User:MinorProphet/Draft subpages/WW2 ZF gearboxes

Zahnradfabrik Friedrichshafen GmbH (ZF) was formed in September 1915 as an offshoot of two existing companies, Luftschiffbau Zeppelin GmbH of Friedrichshafen and Max Maag Zahnradfabrik of Zürich (later Maag-Zahnräder AG), to make gearboxes for Zeppelin airships.{{cite web|title=Alfred Graf von Soden-Fraunhofen |website=Villa von Soden |language=German |url=http://www.villavonsoden.de/Historie.htm |accessdate=25 July 2021}}

File:Bundesarchiv Bild 146-1978-101-14, Zeppelin Katastrophe in Weilburg.jpg after its crewless catastrophe in Weilburg ]]

The head of the testing department at Zeppelin since 1910 was Alfred von Soden-Fraunhofen (21 November 1875–14 June 1944), an engineer and designer who had previously worked at Daimler AG and MAN.{{sfn|Steude|1965|p=99}}{{efn|Not to be confused with {{ill|Alfred von Soden (General)|de}}, who fought in the Boxer Uprising as a naval Lieutenant where he earned the Pour le Mérite medal, and was commander of occupied Liège and Brussels during WW1.}} He became acquainted with Graf von Zeppelin while holidaying in the area, and was offered the newly-created position in 1910. He was involved with testing the Zeppelin LZ 6 and LZ 7 airships in 1910 after the LZ 5 crashed and burned. (See also List of Zeppelins.) Soden and Claude Dornier, also employed by Zeppelin, wrote a report together on airship drag in 1911.{{sfn|von Soden|Dornier|1911}} In search of high-quality gearbox mechanisms to transfer power from Zeppelin engines (designed and made by Maybach), von Soden contacted {{ill|Max Maag|de}}, a Swiss engineer who in 1913 had started his own factory in Zürich to make precision-ground helical gears.{{sfn|Steude|1965|p=106}}

Count Zeppelin prompted Alfred Colsman, managing director of Luftschiffbau Zeppelin GmbH (LZ), to propose a new independent company based in Friedrichshafen, which was founded in 1915 as Zahnradfabrik Friedrichshafen GmbH, a limited liability company with von Soden as managing director. The company made gearboxes for Zeppelin airships during WWI. By 1918 the company had 600 employees, which had fallen to 570 in 1920.{{sfn|Köster|2008|pp=5–6}}

The harsh terms of the Versailles Peace Treaty forbade all military activity and manufacturing, and ZF turned to making gearboxes for passenger vehicles.{{sfn|Köster|2008|pp=5–6}} The general post-war depression threatened bankruptcy, and the firm was re-financed and incorporated as Zahnradfabrik Friedrichshafen AG (stock corporation) in May 1921,{{sfn|Köster|2008|pp=5–6}} with LZ (Luftschiffbau Zeppelin) as the major stockholder. Theodor Winz was the first managing director, with von Soden as technical director, heading the design department for almost 30 years until his death from previously diagnosed leukaemia in 1944.{{sfn|Steude|1965|p=111}}{{cite web |title=Alfred von Soden-Fraunhofen |website=ZF |url=https://www.zf.com/mobile/en/company/heritage_zf/count_soden/biography_count_sode.html |access-date=24 July 2021}} Soden was deeply religious, and never joined the NSDAP.

File:Soden-Getriebe.jpg

The Soden transmission ({{ill|Soden-Getriebe|de}}), a pre-selector, semi-automatic gearbox, was invented in 1921 by Alfred von Soden of ZF. It was fitted in passenger cars, light trucks and railway locomotives and also in the Leichttraktor, the forerunner of the Panzer III tank.

It was shown to the public on 23 September 1921, at the first Berlin Motor Show since the war.{{cite magazine |last=Beisel |first=Werner |title= Mit dem Sodengetriebe 1920 in Wien |magazine=Austro Classic |date=January 2021 |pages=100–105 |language=German |url=https://www.sodengetriebe.de/wp-content/uploads/2021/05/AC2021-01_9S_Sodengetriebe_mo2-nq.pdf |accessdate=25 July 2021}} This gearbox represented a feat of engineering that was far ahead of its time.{{sfn|Naunheimer et al.| 2010|p=17}}Pic at {{cite web|url=https://press.zf.com/press/en/media/media_1977.html |title=First car with Soden transmission |publisher=ZF Press Center |access-date=25 July 2021}} The fore-and-aft gear selector lever is mounted on the dashboard. A series of pre-series ({{lang|de|Vorserienstand|italic=yes}}) gearboxes had already been launched in Vienna in October 1920, aimed at taxis, light trucks and buses. The range included types S2.5, S3, S3.5, and S4 for passenger cars (Pkw, {{lang|de|Personenkraftwagen|italic=yes}}) and type S5L for trucks (Lkw, {{lang|de|Last\kraftwagen|italic=yes}}) A version for railway locomotives, Typ TS18.5, had 5 forward and 5 reverse gears.{{cite web |title=Getriebevarianten |trans-title=Transmission variants |website=Sodengetriebe |last=Beisel |first=Werner |language=German |accessdate=25 July 2021 |url=https://www.sodengetriebe.de/getriebevarianten/ }}

In 1925 ZF introduced the {{lang|de|Einheitsgetriebe|italic=yes}} or 'Standard Transmission' series which consolidated and rationalised ZF's gearbox production down to a few structurally similar designs, with varying maximum torque capacities.{{sfn|Naunheimer et al.|2010|p=16}}

File:LeichttraktorProfile.jpg with Soden transmission]]

Early versions of the forerunner to the Panzer III, the Leichttraktor of c1930, were made by the competing firms of Krupp and Rheinmetall. Krupp decided on a gearbox with 3 forward speeds and one reverse (3+1) in October 1928.{{sfn|Jentz|Doyle|2006a|p=3–10}} Rheinmetall used a 4+1 "heavy-duty 4-speed Soden transmission in 1930, assembled with the transfer case.{{sfn|Jentz|Doyle|2006a|p=3–11}}{{sfn|Leichttraktor manual|1930|p=A6a [pdf 22]}}

Changing gears was effected in two separate stages. First, the driver (anticipating the terrain ahead) moves a small pre-selector lever in a fore-and-aft quadrant into the desired slot. Nothing obvious happens. Secondly, when the new gear is needed, the driver depresses the clutch pedal for a full second. Inside the gearbox, a pre-selected piston at the top of the gearbox moves a selector fork within the gearcase to physically change gears on the shaft; the piston is held in its locating hole by spring pressure. The driver then releases the clutch pedal, and travel continues smoothly and uninterruptedly in the new gear. When changing gear while climbing a gradient, it was important to keep hold of the steering wheel while turning; before reversing; or in a moment of danger.{{sfn|Leichttraktor manual|1930|p=A6a [pdf 22]}}{{efn|Description of gearbox (in German) at {{harvnb|Leichttraktor manual|1930|p=15 [pdf 25] }}. The pre-selector lever is no. 5 in the photo, right on top of the gearbox. The dashboard behind is confusing. Better close-up pic of lever at {{harvnb|Leichttraktor manual|1930|p=[pdf 40]}}. }}

The Soden gearbox was replaced in July 1930 with a "normal transmission",{{sfn|Jentz|Doyle|2006a|p=3–18, 19}} a ZF G55 'Aphon'.{{sfn|Jentz|Doyle|2004b|p=17–4}}

• Combine these two paras!

:Before and during WWII, ZF only made one model of this type of pre-selector, semi-automatic gearbox for a military vehicle, the much more complex 6 EV 75.{{efn|The 6 EV 75 used electromagnetic clutches and was fitted to the Swedish Stridsvagn m/42, but faulty design or manufacture of the clutch plates led to swift mechanical failure. The Swedes made several attempts to improve the gearbox, including the manufacture of replacement clutch plates which controlled the shifting mechanism.}} It was Maybach, ZF's sister company, who pursued the design and development of this type of relatively complex and (at the time) uncommon gearbox, and produced the majority of a small number of types during the war.{{efn|These were installed in the Sd.Kfz. 10 and the derived Sd.Kfz. 250 half-tracks, certain Panzer II and Panzer IIIs, and —most successfully—Tiger I and II tanks.}} ZF also made a few examples of a prototype electromagnetic gearbox, the K 12 E, tested on Panthers and Tigers, which was not put into full production.

:Apart from the Soden transmission used in the Leichttraktor, it doesn't seem that ZF actually made any quantity series production gearbox of this semi-automatic type for military use, except the ill-fated EV series with electromagnetic clutches, fitted to around 100 Swedish Stridsvagn m/42 tanks. In general, ZF made conventional, manual gearboxes, and Maybach made the more complex pre-selective semi-automatic ones.

See also § Overview of gearbox types below.

In 1928 ZF introduced the 'Aphon' transmission (Greek for "without noise" or "noiseless"), a constant-mesh gearbox using helical-ground gears for passenger vehicles. It eliminated the inherent whine of straight-cut gears.{{sfn|Naunheimer et al.|2010|pp=17-19}}

File:Emw327-totale-nah.jpg ]]

The Aphon was designed by Albert Maier (1899–1983).Seherr-Thoß, Hans Christoph Graf von, [https://www.deutsche-biographie.de/pnd119169673.html#ndbcontent "Soden-Fraunhofen, Alfred Freiherr von"] in: Neue Deutsche Biographie Vol. 24 (2010), pp. 521-522 [Online-Version]. Maier graduated from Konstanz Engineering school and joined ZF in 1922, later becoming an engineer in the Design Office.

These first Aphon car transmissions also featured synchromesh (except 1 & R). Transmissions with full synchro on all gears for passenger vehicles such as the AK 4 S series (marketed as Panaphon) appeared in 1934.{{refn|{{Cite web |last=Vogler |first=Janine |title=90 Years of All-Synchronous Transmission |date=25 July 2024 |website=ZF |url=https://www.zf.com/mobile/en/company/strategy/heritage_zf/stories/all_synchronous_transmission.html |quote="The letter "S" stood for synchronization, the first digit for the number of gears and the last for the meter-kilogram of the engine and thus the maximum input torque of the transmission." |access-date=24 March 2025}} }} The AK 4 S-15 was fitted in the BMW 327 from 1936/7 to 1941. {{refn |name="AK4S" |Photo of cutaway 4-speed synchro AK 4 S gearbox, precursor of the AK 7-200 and others. {{cite web |title=Meilensteine der ZF-Geschichte, '1930' section: 1934 - Allsynchrongetriebe |language=German |url=https://www.zf.com/mobile/de/company/strategy/heritage_zf/heritage.html |website=ZF |access-date=26 March 2022}} NB Needs up-date browser}}

Soden and Maier later designed the AK 7-200 gearbox for the Panther tank from 1941.{{sfn|Spielberger|1993c|p=55}}{{cite web |url=https://press.zf.com/press/en/releases/release_3054.html |title=Founders, Decision-Makers, Companions: Influential Figures in ZF History |publisher=ZF Press Center |access-date=22 March 2025}}{{efn| Maier, one of the managers of ZF after WWII also designed ZF's only car, the post-war two-seater Champion with a 200cc supercharged 2-stroke lawnmower engine with 3+1 speed gearbox. He was also a collector of medieval arms and armour.[https://www.zeller.de/de/highlights/sammlung-dr-albert-maier/ Sammlung Dr. Albert Maier]. Auktionshaus Michael Zeller - Auction April 2018 {{dead link|date=March 2025}} }}

ZF produced the the first full synchro gearbox for commercial vehicles in 1957, e.g. the ZF S 6-55 etc.{{sfn|Naunheimer et al.|2010|pp=13, 19}}{{cite book |publisher=Zahnradfabrik Friedrichshafen |place=Friedrichshafen |title=Getriebe-Fibel: Bedienung und Wartung für Allklauen- und Synchrongetriebe |lang=de |url=http://www.ff-zinzendorf.de/wp-content/uploads/2016/10/Getriebe-Fibel.pdf |date=June 1965 }} With humorous illustrations throughout + pic of rebuilt factory

However, the motor industry in Germany during the 1930s was not well developed. There was very little mass-production using assembly-line methods common in the US. Motor cars ({{lang|de|Personenkraftwagen|italic=yes}}, Pkw) were only owned by approximately one per cent (1%) of the population, including businesses, government and richer private individuals. The motor industry was small-scale and scattered over thousands of individual businesses. Approx 90% of all goods travelled by rail,Mierzejewski, Alfred C., (2000). The Most Valuable Asset of the Reich: A History of the German National Railway. Volume 2, 1933-1945. Chapel Hill and London: The University of North Carolina Press, passim.{{page needed|date=May 2025}} and another 8.5% was carried by trucks ({{lang|de|Lastkraftwagen|italic=yes}}, Lkw). The most common mode of personal transport was the motorcycle.{{sfn|Friedli|2010|p=20}} In 1934, 45% of the world's motorcycles were to be found in Germany.{{cite thesis |last=Stinchfield |first=Andrew Lawrence |title=Automobiles, Autarky, and Authority: The Effects of Nazi Centralized Economic Planning, 1932-1942 |date=2013 |type=Thesis |place=Schenectady, NY |publisher=Union College |url=https://digitalworks.union.edu/cgi/viewcontent.cgi?article=1766&context=theses}} According to the historian Adam Tooze, "In 1932 there were only 486,001 licensed cars in Germany. In Berlin, a city of 4 million inhabitants, there were fewer than 51,000 cars."{{sfn|Tooze|2007|p=149}} NB Table may be unnecessary...

Vehicle ownership in Europe and USA, 1935 (per 1,000 pop.)

Country Vehicles Country Vehicles

USA 204.5 Switzerland 21.7

France 49.0 Irish Free State 17.8

UK 45.2 Netherlands 17.6

Denmark 41.6 Germany 16.1

Sweden 24.4 Italy 9.5

Norway 22.3 USSR 1.5

Source: R. J. Overy, [https://archive.org/details/wareconomyinthir00over/page/72/mode/1up?view=theater War and Economy in the Third Reich], (Oxford: Clarendon, 1994), p. 73. NB Requires free registration at Archive.org.

Part of the reason was the cost of fuel: in 1937 one gallon of gasoline in the US cost approximately 20¢ ($0.20)[https://www.titlemax.com/discovery-center/average-gas-prices-through-history/ Average Gas Prices in the U.S. Through History (Updated)] but one litre in Germany cost around 40 Pfennigs,{{sfn|Tooze|2007|p=151 [pdf 178}} approximately 3½ times the price at $0.72 per gallon.{{efn|At around 2.50 Reichmarks to the dollar,{{ref needed|date=May 2025}} and approx. 4.5 litres to the gallon, the equivalent of a gallon of gas in Germany would have cost about $0.72. If 1 litre of gas cost 40 Pfennigs, one gallon (at approx. 4.5 litres to the gallon) would have cost RM 1.80. At RM 2.50 to the dollar, one gallon of gas in Germany {{=}} $0.72.}}

After the rise to power of the NSDAP regime in 1933, the manufacture of military vehicles began again in earnest, and many other German manufacturers manufactured their own engines and gearboxes: but by 1936 the gearboxes for the majority of all tanks and half-tracks were designed and made by ZF, with the majority of engines made by Maybach, another offshoot of Zeppelin also based in Friedrichshafen. ZF and other firms were licensed to make Maybach-designed semi-automatic gearboxes, eg the SRG 32 8 145 for the Panzer III Ausf. E–G.{{sfn|Jentz|Doyle|2007a|p=3–2–11}}

ZF's gearbox model identification system generally consists of one to three letters (e.g. G, FG, SSG), followed by a number indicating the gearbox's approximate maximum torque capacity in kilopondmeters (abbreviated in contemporary documents as mkg or mkp.)

For example, 'SFG 75' stands for Synchronisiert Funf-gang Getriebe (synchronised five-speed gearbox), with an approx. maximum torque capacity of 75 mkg.{{sfn|Jentz|Doyle|2006a|p=3–32}} See also § Torque section.

The numbering of the 'AK' series explicitly includes the number of forward gears and maximum torque, e.g. AK 7-200.

Although all the ZF half-track transmissions included a range reduction gearbox (sometimes called 'hi-lo', or 'crawler' box) either separate or integrated within the casing (resulting in 8 forward and 2 reverse speeds), this is ignored in the model number.

File:Sd.Kfz. 7 Krauss-Maffei pic1.JPG Sd.Kfz. 7. Later production versions (KM m 11) used the ZG 55 gearbox.]]

All the ZF series production half-track gearboxes are manually operated and without synchro, having four forward speeds and one reverse, generally coupled with a hi-lo range box (or 'crawler box') (not included in the designation) to give a total of 8 forward speeds and 2 reverse, abbreviated in this article as (4+1 x 2).

• G = {{lang|de|Getriebe}},{{efn| The neuter noun {{lang|de|das Getriebe}} means "gearbox", the feminine noun {{lang|de|die Getriebe}} means simply "a gear". Compare {{lang|de|die See}} (f.) "ocean, sea", and {{lang|de|der See}} (m.) "lake". }} Four forward + one reverse gears, non-synchro. 'Semi-unit' construction with factory-fitted clutch. Two casings are bolted/flanged together: clutch and hi-lo box casing at the front; and main change-speed box in the rear casing (i fink). Fitted to half-tracks with Maybach HL 'TU' type engines (e.g. the ZG 55 fitted to later models of the Sd.Kfz. 7 KM m9, driven by the HL57 TU) - NB An exception is the G 65 VL230 without factory-fitted clutch in the Sd.Kfz. 9.
• ZG = Z-Getriebe (Zug-Getriebe??) Four forward + one reverse speeds, non-synchro, no factory-fitted clutch. 'Unit' construction with both speed change and hi-lo mechanisms within the same casing. Fitted to half-tracks with Maybach 'TUK' type engines (e.g. HL62 TUK in Sd.Kfz. 7, KM m11), where the 'K' always indicates a factory-fitted clutch. An exception is the ZG 35 fitted in Krupp's export tanks L.K.A and L.K.B. (using a Krupp V-8 engine) which had synchro on at least the first two gears, and a single plate clutch.{{sfn|Jentz|Doyle|2002b|p=1–130}}

File:Panzer IV 1.jpg Ausf. G, which used the ZF SSG 76 with synchromesh.]]

All the series production gearboxes for German tanks made by ZF (including other full-tracked vehicles based on tank chassis, such as self-propelled artillery, tank hunters, assault guns etc.) have five, six or seven forward gears, with synchromesh (except 1st and reverse).

• FG = {{lang|de|Funfgang Getriebe}}, five forward gears + one reverse, synchro on 2nd through 5th.{{sfn|Jentz|Doyle|2002a|p=1–83}}
• SFG = {{lang|de|Synchronisiert[er] Fünfgang Getriebe}}, Synchronised Five-gear Gearbox (synchro on all gears except 1st & R).{{sfn|Jentz|Doyle|2006a|p=3–32}}
• SSG = {{lang|de|Synchronisiert[er] Sechsgang Getriebe}}, synchronised six-gear transmission.{{sfn|Jentz|Doyle|2006a|p=3–50}}
• AK = All-Klauengetriebe{{cite web |title=AK Getriebe: Allklauengetriebe |website=ZF |url=https://www.zf.com/products/de/zf_race_engineering/products_74625.html |access-date=5 October 2024}} ({{langx|de|Klaue}} (tech.) = "claw", "dog clutch", an internal mechanism for shifting gears.){{efn|Since the German words for 'six' ({{langx|de|sechs|label=none}}) and 'seven' ({{langx|de|sieben|label=none}}) begin with the same letter, it is possible that 'AK ' was chosen over the ambiguous 'Synchronisierter Siebengang Getriebe'.}} See also #General overview of gearbox construction. The AK series (whether series production or not) have the number of gears and max. torque stated explicitly in the model number. For example, the AK 7-200 used in the Panther had seven forward gears, the non-production AK 5-80 had five forward gears, and the AK 6 series had six.
• ZF had earlier produced a series of 4-speed manual gearboxes with synchromesh on all gears in 1934, the AK 4 S.{{refn |name="AK4S"}}[https://img.ricardostatic.ch/images/007de00b-25c0-49f6-b1fb-030d29b01895/t_1000x750/zf-4-gang-getriebe-vorkrieg-mercedes-horch-oder-maibach Pic of AK 4 S casing and innards] from [https://www.ricardo.ch/de/a/zf-4-gang-getriebe-(vorkrieg-mercedes-horch-oder-maibach)-1212779836/ Ricardo] The AK 4 S 15 was fitted in the BMW 327 from 1936/7 to 1941.{{cite web |title=BMW 327 |website=BMW Historic Motor Club |url=https://www.bmwhistoricmotorclub.co.uk/cars/bmw-327/ |access-date=6 October 2024}}{{cite web |title=1938 BMW 327 Sport Cabriolet |website=Top Speed |last=Fira |first=Michael |date=9 November 2018 |url=https://www.topspeed.com/cars/bmw/1938-bmw-327-sport-cabriolet/ |access-date=5 October 2024}}

;Other tank gearboxes:

File:Stridsvagn m42 Revinge 2012-2.jpg, fitted with the problematic 6 EV 75 with internal electromagnetic clutches]]

• 6 EV 75 (6+1) - Electromagnetic gearbox with synchromesh, fitted to Swedish Stridsvagn m/42 tanks. Seen as very unreliable (due to poor quality steel in manufactured internal clutch plates, perhaps not the basic design...)
• SMG = ?? This was a series of experimental, non-production gearboxes.{{refn |name="SMG90"}} For example, the SMG 90 had eight forward gears and possibly semi-automatic operation.{{efn| Although Jentz and Doyle state this was made by Maybach, the 'SMG 90' style of designation is specific to ZF: Maybach's numbering system was consistently much more detailed (eg the 'Olvar' OG 40 12 16 indicating approximate max. power in PS, max. torque in mkg, and total gearbox reduction ratio.) }}

Almost all the gearboxes fitted to tanks included a clutch as standard,{{efn|There was generally no room for a clutch in the cramped rear engine compartment of a tank, and a cardan shaft ('prop shaft') connected the engine to the gearbox via a clutch (either bolted-on, or integral with the gearbox casing) at the front of the vehicle.}} as well as some half-track gearboxes (e.g. for many early Sd.Kfz. 6 variants.) The ZF SSG 76 and 77 (both supplied with a clutch from the factory) were installed in the pre-production Panzer III Ausf. A–D{{sfn|Perrett|1980|p=5}} and the Ausf. H–N respectively.{{sfn|Koch|2000|p=20}}{{sfn|Perrett|1980|pp=6–9}} Between these two series, the ill-fated semi-automatic Maybach SRG 32 8 145 was used in the Panzer III Ausf. E–G. Maybach's own modified clutch was fitted at the factory as a option: and thus the Maybach HL108 TR and HL120 TRM engines (differing between the Panzer III and Panzer IV tanks) could be ordered from the manufacturer with or without a clutch, depending on the gearbox.{{cite web |title="478. WH Dienstvorschrift Maybach HL 120 TRM Ersatzteilliste \ Wehrmacht Manual: Maybach HL 120 TRM spare parts list" |url=https://bushmakow.com/library-cat/maybach-motoren/ |via=Bushmakow.com |publisher=Maybach Motoren |place=Friedrichshafen |series=Nm 261/237 5.43.25 |access-date=16 March 2025 |quote=On title page: Beachten: Ausführung "A" oder Ausführung "B".}}{{cite web |title=487. Heft 90 D Maybach HL 108-120 TR TRM Panzer |url=https://bushmakow.com/library/487-heft-90-d-maybach-hl-108-120-tr-trm-panzer/ |via=bushmakow.com |access-date=5 October 2004}}
Official Memorandum including engine parts list; Appendix [pdf 35] listing all the different engine parts to be supplied for each Ausf. of all Panzer III and IV tanks; and illustrations [pdf 43].

With the exception of 'EV' and 'SMG' gearboxes above, it appears that all of the transmissions which ZF produced for installation in German tanks, halftracks and other military vehicles were manual: all the pre-selector, semi-automatic gearboxes fitted to some German tanks and the Sd.Kfz. 10 etc. as mentioned above, were designed by Maybach (their SRG, VG, & OG series), with some made under license by ZF and others.{{efn|The ZF Soden gearbox used mechanical (spring) pressure to control the shifting; the VG was pneumatic/vacuum actuated; the SRG used vacuum for the selector valves/pistons, and hydraulic pressure for the accelerator & brake clutches; and the OG was completely hydraulic. NB! Copy to Maybach g/box draft! }}

Good website about the Panzer IV: [https://panzerivuniverse.phelpscomputerservices.com/Default.htm Panzer IV Universe] with lots of refs.

File:Panzer III Ausf. F U.S. Army Armor & Cavalry Collection.jpg

Tanks etc. which did not use a ZF gearbox included the Panzer II Ausf. D & E,{{efn|Many Ausf. D & Es were converted to (or built as) Panzer II(Flamm.) flamethrowers, and subsequently to Marder IIs.{{sfn| Jentz|Doyle|2010c|pp=2-3-6, 11}}{{sfn|Jentz|Doyle|2005a|p=7–80}} }} which used the pre-selector, semi-automatic, Maybach SRG 14 4 79 (7+1);{{sfn|Spielberger|1974|p=102 + Appendix p. 151}} the Panzer III Ausf. E-G which used the troublesome Maybach SRG 32 8 145 (10+1);{{sfn|Jentz|Doyle|2007a|pp=3-2-36 to 38}} and production models of the Tiger I, Tiger II and derivatives, which used the Maybach Olvar OG 40 12 16 (8+4).{{sfn|Jentz|Doyle|2000b|p=181}}{{sfn|Jentz|Doyle|1997b|pp=23, 26, 164 [pdf 158]}}

Half-tracks which did not use ZF gearboxes included the Sd.Kfz. 10 and Sd.Kfz. 250, fitted with the pre-selector, semi-automatic Maybach VG 10 2 128H (7+3);{{sfn|Spielberger|1993a|p=157}} and all Sd.Kfz. 11s and Sd.Kfz. 251s, which used Hanomag's own manual 4+1 x 2 gearbox designs.{{sfn|Spielberger|1993a|p=158}}

All refs from Walter J. Spielberger, Die gepanzerten Radfahrzeuge der d. Heeres 1905–1945 Motorbuch Verlag Stuttgart (1991) ISBN 9783879433377 {{sfn|Spielberger|1997}}

• The amazing [http://www.leadwarrior.com/Lw35210-h.htm Magirus Mannschafts Transportwagen I] (8-wheel, Achtrad-Wagen ARW), 1927-9 had a "ZF Wendegetriebe" (ie reverse gear unit) p. 142 [pdf 140]. Hugely expensive, replaced with the 6-wheel Sd.Kfz. 231.
• Schwerer Panzerspähwagen Sd.Kfz. 231 and (Fu) 232 (8-rad) made by Magirus (type M 206P) used a ZF Umkehrgetriebe (ie 'reversible gearbox'). p. 150 [pdf 148] The 8-wheeled armoured cars could be driven in either direction, with full driving controls at each end.
• The Daimler-Benz (Fu) Sd.Kfz. 232 (type G3a/P) used a Maybach DSG 40 vacuum. p. 152 [pdf 150].
• The schwerer gelandegänginger gepanzerte Personenkraftwaken (s.gl.gp.PKW lol) Ausf. A (6-Rad) Sd.Kfz. 247 made by Krupp (only 10 made pre-war) used a "ZF Aphon Gb 35 bL + GG35". p. 159 [pdf 157]

Need incorporating into the tables...

Zahnradfabrik Friedrichshafen (ZF) designed and produced the gearboxes for the vast majority of German tanks and half-tracks during World War II, shown in the tables below.

Gearboxes which reached series production are shown in Table 1: experimental or test (versuchs) gearboxes are shown in Table 2.

[https://bushmakow.com/library/139-d-655_2-panther-ausf-a-d-u-g-befehls-panther-ausf-a-d-u-g-bedienungsanweisung-z-turm/ Dienstvorschrift D.655/5, Panther driver's manual], pp. 18 and part D, Bild 22 - 24 shows that it the AK 7-200 is definitely a standard synchro manual gearbox.

None of the gearboxes listed here, and very few of the vehicles they were tested in, actually reached series production during the war.{{efn|In the 1950s/60s ZF sold the AK series as pneumatically controlled pre-selector gearboxes (with a similar mechanism to the Maybach types) for commercial trucks, either without synchromesh (e.g. the AK 5-35) or with synchro (e.g. the S 6-70).[http://www.ff-zinzendorf.de/wp-content/uploads/2016/10/Getriebe-Fibel.pdf Getriebe-Fibel]}}

{{main|Manual transmission|Semi-automatic gearbox}}

The general terminology of gearboxes may differ considerably by country. Gearboxes are often called transmissions, although the latter term is often colloquially used by mechanics and others to refer to the complete drivetrain by which power is transmitted from the engine to the driving whelks wheels. In modern terms, this may include the gearbox (which may be separate or of unit construction with the engine}, propeller shaft (or Cardan shaft, or simply 'prop shaft') and final differential gear. There are many implementations of this overall concept.

This article interchangeably uses both 'gearbox' and 'transmission' to refer only to a speed-shift mechanism. In this context, the gearbox or transmission is almost always a separate unit, either flanged directly to the engine (as in the half-tracks mentioned here) or powered by a prop shaft from the engine which is usually located at the rear of the vehicle.

The term 'transmission' may also include a separate 2-speed manual transfer gearbox, although no Wikipedia article appears to accurately define this specific simple mechanism. It is sometimes called a reduction gearbox ({{lang|de|Untersetzergetriebe}}) although not necessarily of planetary construction, 'transfer case' 'hi-lo box', or 'crawler box', also often found in agricultural tractors. For the purposes of this article this type of reduction gearbox was fitted to most of the WW2 German half-tracks (except the Sd.Kfz. 10), providing a second set of low ratio speeds when very low speed and high torque was needed, such as hauling disabled vehicles out of a ditch, mud, etc. In the ZF transmissions under discussion here, the reduction box may be of separate construction and flanged to the rear of the change-speed gearbox, or of unit construction within the gearcase. This article does not discuss the differentials, steering gear or braking systems installed in tanks etc. made by other manufacturers.

File:Crash gearbox 3gears and reverse.gif

File:Gearbox 4gears.gif

• A) Manual transmission
• 1) Sliding-mesh type ({{langx|de|Schubgetriebe}} or {{lang|de|Schubvorgelege}}). This is one of the oldest gear change mechanisms, dating back to at least 1906.[https://repozytorium.biblos.pk.edu.pl/redo/resources/38408/file/scans/DEFAULT/OCR_rezultaty/100000299536_A_v1_200dpi_q60.pdf Der Motorwagen und seine Behandlung] (in German) p. 89 [pdf 103]) The gears are physically moved up and down the (input) shaft ({{langx|de|Welle}}) to engage with the corresponding gear on the (output) shaft. Almost always without synchro, and often called a 'crash box'. Skilful double de-clutching is needed to effect gear changes without 'crunching' the gears as they mesh at different speeds. Very often the gears are straight-cut, which produces a pronounced whine.

::None of the ZF transmissions listed here are of this type, although various gearboxes are briefly described by historians (eg Spielberger) as "Schub-", perhaps possibly to distinguish from synchro boxes.{{efn|Jentz & Doyle in Panzer Tracts 23 {{sfn|Jentz|Doyle|2011|p=23–5}} state that Spielberger only worked in the USA, perhaps without access to original documents. J & D used only original documents. Try their Sd.Kfz 251.}}

• 2) Constant-mesh ({{langx|de|Klauengetriebe}}) type. As the name suggests, all the gears are constantly in mesh. Instead of shifting an entire gear wheel on a shaft, a selector fork moves a dog clutch (in purple in the diagram) on a shaft between a pair of gear wheels. All the ZF transmissions listed here are of this type, with or without synchro, and all with helical-cut (or helical-ground) gears.
• ZF's trade name for this type of transmission was § 'Aphon' (Greek for "without noise" or "noiseless"), a helical-ground constant-mesh transmission introduced in 1928 for passenger vehicles. It eliminated the inherent whine of straight-cut gears.{{sfn|Naunheimer et al.|2010|pp=17-19}}See also ZF site
• 3) Synchromesh gearbox or 'synchro' ({{langx|de|Synchrongetriebe}}) type. A development of the constant-mesh gearbox which eliminates the need for double de-clutching by the incorporation of 'synchro rings' between the dog clutches. The rings absorb the speed difference between the two shafts, essentially acting like basic automatic inline clutches. Almost all ZF gearboxes fitted to tanks etc. were of this constant-mesh synchro type.
• eg Aphon SSG 45 synchro in the Panzer II, SFG 75 & eg SSG 76, Panzer III & IV etc.
• 'AK' (Allklauen) series ({{langx|de|Klauen}}, 'dog clutch'), were all synchro - eg AK 7-200 (7+1) for all Panthers. Also experimental AK 6-200 (6+1) & 5-200 (5+1) for later high-revving experimental Maybach HL154 etc. engines - neither the prototype engines nor gearboxes ever reached series production during WW2.{{efn|ZF Allklauen series continued after the war as a commercial pneumatic pre-selector g/box, eg the ZF S 6-55[http://www.ff-zinzendorf.de/wp-content/uploads/2016/10/Getriebe-Fibel.pdf Maybach post-war catalogue Getriebe-Fibel] which included technology from Maybach's Variorex.}}
• B) Semi-automatic gearboxes.
• Preselector gearbox type. Apart from the unsuccessful 6 EV 75 (see below), ZF doesn't appear to have made any series production of this type during the war, although it seems likely that they worked with Maybach on the designs of various models (eg SRG, Variorex and Olvars.) See List of WW2 Maybach gearboxes.{{efn|I deffo found somewhere a manufacturer nameplate on a 'box saying 'made by ZF under licence from Maybach' I fink the Tiger Olvar gearboxes were made by ZF? No, it was the Maybach SRG 328 145, production was outsourced to ZF.{{sfn|Jentz|Doyle|2007a|p=3–2–11}} }}
• ZF Electro series - used internal electro-magnetic clutches, eg ZF 6 EV 75 (6+1) fitted to c.100 production Swedish Stridsvagn m/42 tanks in 1943–1944 (very unreliable - see table); and ZF K 12 E 185 proposed for late model Panthers but never reached series production.{{sfn|Spielberger|1993c|pp=162–3, 174}}

;Summary:

• The 'G' and 'ZG' gearbox series installed in some half-tracks are all non-synchro.
• All the ZF gearboxes fitted to a number of half-tracks had manual, non-synchro transmission with 4 forward + 1 reverse gears, coupled with a hi-lo range transfer box giving a total of 8 forward and 2 reverse speeds. This is expressed as (4+1 x 2). Some early models of the Sd.Kfz. 6 had a further hi-lo reduction box giving 12 forward and 3 reverse speeds. NB Spielberger in the English version of Halftracks has some very differing views, but I suspect he (and/or his translator) is completely in error. See talk. Some sources say that the Sd.Kfz. 9 may have had a synchro gearbox, but this is almost certainly incorrect.
• Not all gearboxes fitted to half-tracks were made by ZF: eg the Maybach pre-selector Variorex in the Sd.Kfz. 10/250; and Hanomag installed their own gearbox in the Sd.Kfz. 11 and 251.{{harvnb|Spielberger|1993a}} Halbketten in German, although the English edition makes some outlandish statements) J&D, Pz. Tracts, p. 22-2-7 state that a late trial version (not made in quantity), the H7, used a Maybach pre-selector box. Not further discussed. In some cases the range box is completely or semi-separate, as in the early 'G' series; and if of unit construction, the 'ZG' series (and, illogically, the G 60 in the Sd.Kfz. 9).

• The 'FG',{{cn|date=March 2022}} 'SFG', 'SSG' and 'AK' series, installed in many other tanks and SP gun carriages etc., are all synchro (except 1 +R).
• Despite Spielberger's list in Halftracks of the German Army, ZF don't appear to have made any pre-selector gearboxes at all except the electromagnetic 'E' or 'EV' series, and they weren't a success (although due to manufacturing faults rather than design.)
• See the interesting and fruitful discussion Talk:Sd.Kfz. 8, the reason for this article.

Gearboxes (colloquially, simply 'boxes') are generally designed to transmit a specific maximum torque.

The unit of torque used in Germany at the time was the Kilopondmetre, abbreviated as mkg in contemporary literature (sometimes mkp): modern abbreviations are kp·m or m·kp. 1 mkg = 9.80665 N·m = 7.233 lb·ft

• Torque (lb.ft) = 5,252 x power (hp) / speed (rpm)
• Torque (N.m) = 9.5488 x power (kW) / speed (rpm)
• Torque (mkg) = 716.19724 x power (PS) / speed (rpm) (thanks to GNU Units and the [https://en.wikipedia.org/w/index.php?title=Wikipedia:Reference_desk/Science&oldid=1035012324 Science Ref desk])

Max. torque of an engine is often reached at lower revs (approx 2/3 max revs) than maximum power, eg 2,000 rpm vs 3,000. Refs needed... Diesel engines (inherently lower-revving through their basic design) produce max. torque at lower revs than a petrol engine, although diesels were not fitted to most German armoured vehicles.

ZF's naming scheme almost always indicates the rated torque of the gearbox - eg the SSG 45 was designed for Maybach HL62 TR's max torque output of 45 mkp/mkg.{{sfn|Spielberger|1974|p=71}} In some cases the gearbox was uprated to handle a greater torque, but kept the same model number.Ref pls! Similarly, the AK 7-200 was apparently designed for the HL210/230's max torque of c.200 mkg.

• I think I need a list of engines and/or gearboxes whose max. torque (Md. = {{lang|de|Maximaldrehmoment}}) are definitely known. (Done: see Talk.) Spielberger's Panther tank and variants includes Appendix 18 with lots of original diagrams, graphs etc., including HL108 and HL230. NB! My thoughts below about tractability and flat torque curves may be completely wrong. They say (i fink) that a noticeable torque rise through the rev range with more gears, is equivalent(?) to a flat torque curve with fewer gears. Or something. Check, fool!

In tank and prime mover engines, the maximum power of an engine may be rather less important than its maximum torque.

Insert stuff about the relationship between the two. Not particularly easy to explain. Sports analogy: a bit like having a load of rugby players to haul you through the mud rather a bunch of sprinters to achieve maximum speed. See Büffel-Charakteristik, 'Buffalo characteristics' (Spielberger, Panther tank and variants, p. 236)

:"A flat torque curve makes an engine much more driveable because acceleration is the same at any point on the curve. Transmission can be less complicated, not more. Engines with peaky torque curves require a lot of gears as acceleration is maximum only in a narrow rpm range.It is just difficult to get with max hp output." Put another way, a flat torque curve is desirable in a tank engine. More info needed.

:"Torque can be increased by increasing the mean effective pressure of the engine, or by lowering the torque losses." [https://x-engineer.org/automotive-engineering/internal-combustion-engines/performance/power-vs-torque/ power vs torque] Includes lots of graphs for various fuel-injected spark car engines.

{{see also|List of WWII Maybach engines#Clutch}}

Clutches, like gearboxes, are designed to transmit a specific torque from the engine to the drivetrain. The firm of Fichtel und Sachs (see also :de:Fichtel und Sachs) supplied the majority of factory-fitted clutches either for ZF gearboxes or for Maybach engines/gearboxes where specified.

Most of the ZF gearboxes fitted to tanks (and SPGs, tank hunters etc.) discussed here were delivered to the various manufacturers' assembly plants with a clutch attached. These were connected by a prop shaft to Maybach engines without a 'K' in the model number (e.g. HL62 TR used in some Panzer IIs). There is at least one exception: a clutch was bolted to the HL120 TRM motor in the Panzer III Ausf. H and onwards, not to the SSG 77 gearbox.{{efn|{{harvnb|Jentz|Doyle|2007a|p=3–2–70, 71}} Jentz uses the term {{lang|de|angeflanscht}}, 'flanged', meaning the two components are bolted with a gasket to form a seal.}} Maybach engines with a 'K' in the model number, almost all used in half-tracks (e.g. HL108 TUKRM in later Sd.Kfz. 9s) indicate that the clutch was fitted as standard by Maybach.

Although a number of sources (mostly websites) claim that some ZF gearboxes used planetary gears, this never appears to be the case, although some differentials and final drives (not made by ZF) did.

The final drive and steering mechanism used in the Panther is one such device, developed at MAN. Although this article is about change-speed gearboxes, there is a good of description of the Panther's final drive in

• {{cite book

|last=Ogorkiewicz

|first=Richard M

|title=Technology of Tanks I

|date=1991

|publisher=Jane's Information Group

|place=Coulsdon, Surrey, UK

|isbn=0-7106-0595-1}} pp 280–283, [294–7] with diagram 12.10 on p. 281.

The author describes it as "a much more elegant form of multi-geared steering" which may be true but they often only had a fatigue life of 150km or so. See List of WWII Maybach engines#Development of the HL210 and HL230.

;END OF MAIN ARTICLE TEXT

;Notes

{{notelist}}

;Citations

{{reflist}}

{{columns-list|colwidth=20em|

• {{cite web |ref={{harvid|Leichttraktor manual|1930}} |last=Anonymous |date=c. 1930 |url=https://tanks.mod16.org/pdf/leichttraktor.pdf |title=Leichttraktor manual |language=German |accessdate=25 July 2021}} - Dude, sort this one out at least...

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• {{cite book

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• NB This volume gives Jentz and Doyle's final production estimates for most of the German fighting vehicles covered in their earlier Panzer Tracts series and other publications. The authors state they had not completely understood the complexity of the original documentation. It is essential to use this book in conjunction with any other Panzer Tracts volume to ascertain the correct production figures.

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• {{cite book

|ref=

|last=Perrett

|first=Bryan

|others=Illustrated by David E. Smith and Mike Chapell

|date=1980

|title=Panzerkampfwagen III

|place=London

|publisher=Osprey Publishing|isbn=0-85045-362-3}}

• {{cite book

|last1=Sawicki

|first1=Robert

|last2=Ledwoch

|first2=Janus

|title=Mittlere ZgKw 5t: Sd Kfz 6

|place=Warsaw

|publisher=Wydavnictwo "Militaria"

|language=Czech, English

|year=2007

|isbn=9788372192875}}

• {{cite journal

|last1=von Soden

|first1=Alfred

|last2=Dornier

|first2=Claude

|title=Mitteilungen des Luftschiffbau Zeppelin in Friedrichshafen: Die Bestimmung des Schiffwiderstandes durch Farhtversuch

|trans-title=Determination of airship resistance through flight tests

|journal=Zeitschrift fur Flugtechnik und Motorluftschiffahrt

|language=German

|volume=2

|date=1911

|url=https://catalog.hathitrust.org/Record/000553396

|url-access=limited}} (US access only)

• {{cite book

|last=Spielberger

|first=Walter J.

|title=Die Panzerkampfwagen I und II und ihre Abarten

|others=Illustrated by Hilary L. Doyle and Uwe Feist

|publisher=Motorbuch Verlag Stuttgart

|language=German

|date=1974

|isbn=3879433356}}

• {{cite book

|last=Spielberger

|first=Walter

|title=Die Rad- und Vollketten Zugmaschinen des deutschen Heeres 1871-1945

|others=Illustrated by Hilary L. Doyle

|publisher=Motorbuch Verlag Stuttgart

|language=German

|date=1978

|isbn=3879435286}}

• {{cite book

|last=Spielberger

|first=Walter J.

|title=Die Halbkettenfahrzeuge des Deutschen Heeres 1909-1945

|edition=4th

|others=Illustrated by Hilary L. Doyle and Uwe Feist

|publisher=Motorbuch Verlag Stuttgart

|language=German

|date=1993a

|isbn=3879434034}}

• {{cite book

|last=Spielberger

|first=Walter J.

|title=Panzer IV & its variants

|others=Illustrated by Hilary L. Doyle and Uwe Feist. Translated by Edward Force

|place=Atglen, PA

|publisher=Schiffer Military/Aviation History

|date=1993b

|orig-date=1977

|isbn=0887405150}}

• {{cite book

|last=Spielberger

|first=Walter

|title=Panther & its Variants

|others=Illustrated by Hilary L. Doyle and Uwe Feist

|place=Atglen, PA

|publisher=Schiffer Military/Aviation History

|year=1993c

|isbn=0887403972 }}

• {{cite book

|last=Spielberger

|first=Walter J.

|title=Sturmgeschutze: Entwicklung und Fertigung der sPak

|others=Illustrated by Hilary L. Doyle and Uwe Feist

|edition=2nd

|publisher=Motorbuch Verlag Stuttgart

|language=German

|date=1994

|isbn=3613013568}}

• {{cite book

|last1=Spielberger

|first1=Walter J.

|others=Illustrations by Hilary L. Doyle and Uwe Feist

|title=Die gepanzerten Radfahrzeuge des deutsches Heeres 1905-1945

|publisher=Motorbuch Verlag

|place=Stuttgart

|date=1997

|lang=de

|isbn=978-3-87943-337-7}}

• {{cite book

|last=Spielberger

|first=Walter

|title=Der Panzerkampfwagen Tiger und seine Abarten

|others=Illustrated by Hilary L. Doyle

|edition=6th

|publisher=Motorbuch Verlag Stuttgart

|language=German

|date=1998

|isbn=3879434565}}

• {{cite book

|last=Spielberger

|first=Walter J.

|title=Panzer III and its Variants

|date=2007

|place=Atglen, PA

|publisher=Schiffer Publishing

|isbn=978-0887404481}}

• {{cite book

|last=Spielberger

|first=Walter J.

|title=Halftracked Vehicles of the German Army 1909-1945

|publisher=Schiffer Military History

|place=Atglen, PA

|date=2008

|asin=B013RODT6M}}

• {{cite journal

|last=Steude

|first=Heinz

|title=Graf von Soden-Fraunhofen

|journal=Tradition: Zeitschrift für Firmengeschichte und Unternehmerbiographie

|language=German

|date=June 1965

|volume=10. Jahrg.

|issue=3

|pages=97–111

|publisher=Verlag C.H.Beck

|jstor=40696961}}

• {{cite book

|last=Tooze

|first=Adam

|author-link=Adam Tooze

|title=The Wages of Destruction: The Making and Breaking of the Nazi Economy

|place= New York

|publisher=Viking

|date=2007

|url=https://archive.org/details/wagesofdestructi0000tooz

|isbn=9780670038268}}

}}

:Category:World War II tanks of Germany

• [https://www.youtube.com/watch?v=5T9LC_jc8Cs Panther Tank's Steering and Gearbox conical Synchromesh] on Youtube
• [https://www.youtube.com/watch?v=k9NCPthmTsU Panther Tank Transmission details] on Youtube
• [https://kedoki.livejournal.com/95606.html Zahnradfabrik 12 E 170] by Kedoki (in Russian)
• [https://kedoki.livejournal.com/124326.html Report on Interrogation of Dipl.-Ing. Ernest Kniepkamp (tank engines)] Transcription of BIOS report