GM F40 transmission

The GM MR6/F40 six-speed manual transaxle was first developed for Fiat, and use after by OPEL and Saab applications. Originally a design developed for Fiat, Opel and Saab applications, the F40 (MT2) is a GM Powertrain - Europe six-speed manual transaxle built by Opel in Rüsselsheim am Main, Germany. Its first use in a North American application was the Pontiac G6 for the 2006 model year. It is also used in some Saab 9-3 and 9-5 models.

The F40 has a three-axis design, with first, second, fifth, and sixth gears on an output shaft behind and below the input shaft, and third and fourth gears are on an output shaft in front of and above the input shaft. Both output shaft pinions drive a helical gear with a conventional differential. The clutch is mounted on a dual-mass flywheel to dampen vibrations on whichever output shaft is idle depending upon which gear is selected.

Triple-cone synchronizers are used on 1st and 2nd gears. These synchronizers have three friction surfaces, which increase their ability to transfer the flow of torque more smoothly from one gear to another. Synchronizers act as clutches to speed up or slow down the gearsets that are being shifted to, and greater friction area results in easier shifting for the driver. The 3rd, 4th, and reverse synchronizers are double-cone, while the 5th and 6th gear synchronizers are single-cone. All of the friction surfaces on the Synchronizer rings are sintered bronze. The ratios in the 6-speed are widely spaced for versatile performance and efficiency.

To adapt the F40 to North American applications and maximize performance, 3rd through 6th gears have been changed to higher-ratio gears starting in 2007 model year. The ratio for 3rd gear is now 1.37:1, and the ratio for 4th gear is no longer an overdrive, with a new ratio of 1.05:1. The 5th gear ratio is 0.85:1 and the 6th gear ratio is 0.71:1.

The addition of a ball-and-spring-type detent on the shift sleeve and detents on the shift rail assists the driver in shifting quicker. The detent raises the force required to move the shift lever which prevents excess movement of the shifter by the driver, and reduces the chance of double bump. Tension between the shift sleeve and the shift rail also prevents the sleeve from vibrating while in gear.

The F40 is cast in aluminum, and weighs 124 pounds (56.2 kg). It has been certified for up to 295 ft-lb ( 400 Nm) of engine torque.

The F40 MT2/MU9 uses a Castrol Burmah (BOT 0063) manual transmission fluid, or GM 88862472 gear oil. This gear oil is identified in GM documentation as a synthetic 75W-85 GL-4. No maintenance is required for normal operation.

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