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A look at Ford and GM's jointly built 6T40 Transmission

Tuesday, March 1, 2016 - 08:00
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Oct. 10, 2002, Ford and GM announced that they would join together to develop a new six-speed front wheel drive automatic transmission. Working on this project together would not only offer a cost-saving factor in its development, they could bring a new transmission to market sooner. Production began in 2006 for a few of their 2007 model year vehicles. Ford builds what they call the 6F35, 6F50 and the 6F55 transmission. GM builds the 6T30/40/45 and 50, as well as the 6T70 and 75 transmissions. The first vehicles Ford placed their transmissions in were the 2007 Edge and Lincoln MKX. GM began using their transmissions in the Saturn Aura, Outlook, Pontiac G6 and the GMC Acadia vehicles.

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Interestingly enough, Ford and GM must have enjoyed the experience as they have joined together again to develop an all-new generation of advanced 9- and 10-speed transmissions for cars, crossovers, SUVs and trucks. They expect to go to production in 2016 for some of their 2017 model year vehicles.

A little about GM’s 6T40 transmission (Figure 1) — a second design (Generation 2) arrived in 2012, which consisted of both software and architectural changes. Pressure switches were eliminated from the TEHCM, solenoids went from being variable bleed to variable feed type, and the valve body and many internal parts have changed with Generation 2 design. By this time (2014-2015), all 6T series transmissions should be converted to the Generation 2 design.

Figure 1
Figure 2
Figure 3

SAE International’s 2011-01-1428 paper entitled “Gen 2 GF6 Transmission Hardware and Controls Updates” states that the first generation of transmissions was analyzed for potential enhancements in an effort to increase fuel economy and improved shift quality.

Changes were made with architectural hardware controls in conjunction with system software to increase capacity, reduce system delays (optimize system response times) and increase efficiency.

One example of an architectural change is with the 4-5-6 clutch. The wave plate was removed and an additional friction was added for increased torque capacity (Figures 2 and 3).

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