RedWS6 00

Hi, I have gone through many posts on here, all say in the Manual transmission we should use Auto Transmission Fluid. Many posts talk bout different forms of ATF. So I guess that tellsme something... use ATF.
I have a whinning noise from the transmission, as ATF is so thin it dosn't protect bearings well, (so I been told), so spoke to a transmission person, who dosn't know much about our transmissions, but said use 75w90, its good for modern cars, high performance carsand trucks, ans reduces whinning. So he talked me into buying 4 quarts of the stuff. Just about to go down the garage today to put it in, but thought I'd check here first.

So my guestion is is it safe to run 75w90 gear oil in the Manual Transmission? what would go wrong? what are the numbers for Dextron III are they close to 75w90?

MeentSS02

iTrader: (11)

The Tremec T-56 definitely specs Dexron III ATF as the fill - I currently run Mobil 1 ATF in mine, and it is 7.6 cSt at 100C, and 34 cSt at 40C. Something thicker would be Pennzoil Synchromesh, at 9.1 cSt at 100C, and 42 cSt at 40C.

Find the cSt numbers at 100C and 40C and compare to what I just listed. Higher numbers means it is thicker.

Personally, I wouldn't want to run an oil that was not spec'd for the transmission simply due to the cost of an overhaul. These trannys are not cheap. Plus, damn near all the old school guys I've ever been around when talking about this transmission would have guessed that it took a heavier weight oil. It just simply isn't the case.

RedWS6 00

Thanks for the info, I think that 75w90 oil is more for the rear diff. Its probably too thick for the transmission. The people I was speaking too knew more about the older cars so I guess its best to get info on here.

Thanks for your help anyway. I'll stick with Dextron III or some other ATF spec'd on here.