F35 transmission

It weighs approximately 99 lb/45 kg and uses 2 quarts/1,9 l of GM 88862472 gear oil. This gear oil is identified in GM documentation as a synthetic 75W-85 GL-4, Castrol Burmah (BOT 0063) manual transmission fluid, and is validated as "fill-for-life". No maintenance is required for normal operation. The gearbox is rated for 260 ft-lb (353 Nm) of engine torque.

The GM transmissions are usually numerically designated in newton metres that means F35 is rated at 350 Nm, the weaker rod shifted SAAB version of the F35, the F25, at 250 Nm, F40 at 400 Nm, M32 at 320 Nm, and so on.

A limited-slip differential is available for high-output applications. GM has sourced Quaife's automatic torque biasing (ATB) torque-sensing (Torsen-style) differential, which is an all-mechanical geared unit that uses no clutch packs or preloading to transfer torque from one axle to the other. The torque transfer occurs automatically and gradually when one wheel loses traction. This type of differential can severely reduce the effects of torque-steer.

The gearbox has shown to hold more power than the factory stated quite reliably. That being said, a lower geared final drive helps eliminate excessive stress on the gears; thus the 3.82 FD (final drive) is weaker than the 4.05 and the now hard to source 4.45 gearset is the strongest. The transmission can still break, especially with a fast spooling turbo to create a low end boost spike. The most common gear to break is third, and commonly a boost ramp is tuned in to help prolong the stock transmission. In general, the transmission will hold up better if the boost comes in later so it is not a sudden surge of power. Wheel hop is a killer of transmissions and axles, creating excessive stress as the wheels load and unload.

3.61 final drive is used on Saab 9000 2,3l engines with turbocharger, other final drive rations used on early cars is 4,21, 4,05, 3,82 and 4,45 (non turbo).