Originally Posted By: onion
Originally Posted By: BearZDefect
Not to sound thick here, but don't many FWD manual and automatic transmissions have the differential sharing the same lubricant? Is this differential less stressed than what Pablo suggests in "Because simply put a transmission is not nearly as stressed as a differential."
In vehicles with transverse-mounted engines (typical American and Japanese fwd cars), the differential generally uses helical gears. Whereas the differentials used with longitudinally-mounted engines (which Pablo is referring to) use hypoid gears in all modern automotive applications... seeings how the torque has to make a 90 degree turn.
The 1980s-early 1990s Saab 900 had FWD and a longitudinal engine. The AT was filled with Ford Type F, but at the hypoid gears, there was a separate reservoir that required 80w90 GL-5 gear oil.
The Chrysler LHS and Dodge Intrepid had a longitudinal engine and FWD. The AT took ATF+3 or ATF+4, but the differential was separate, and required 80w90 GL-5 gear oil.
The 5th generation VW Passat had a longitudinal engine and FWD with AWD being optional. I never saw an AWD Passat, but every FWD Passat had an AT filled with some proprietary ATF, then the differential was seperate. It called for something unique: SAE 80 GL-4.
Most subaru cars have a longitudinal engine, and in the cases of Manual transmissions, GL-5 oil is required. Automatics called for Dexron ATF, and there was also a separate reservoir for GL-5 oil. Viscosity varied by temperature. SAE 90 when temps would not drop below freezing, SAE 80w90 for almost all temperatures, and SAE 75w90 in extreme cold.
In short, ATF can't lubricate a hypoid diff of any kind, and GL-5 is almost always required, with very few exceptions.