Trans oil?

[beltman]

Let me start by saying that I have done all the reading that I can on the subject and I still dont know for sure. I picked up a new to me 1979 CJ7 a couple of weeks ago. The PO didnt have any records and this thing was leaking from every gasket so I am changing all the fluids and some gaskets. So far I have done the valve cover and the oil pan. Now I want to change the Transmission fluid. I am thinking napa 85w90 GL4 or Mobil 1 75w90. Cost is no problem. This jeep is my every day driver. I live one mile from my work also I live in northern Illinois so it gets cold in winter. Also very little off road for now. I have a stock AMC 258 i6 / 4.2l with a 3 speed T-150 I think. Thank you very much for any help.

 

[yleefox]

Hi,
I borrowed this from Novak Adapters website. I hope it helps you out. Of course, you should make sure that you have the T-150 3 spd Transmission , since it is possible that someone may have changed it at some point in the Cj's life. Novak's website offers plenty of information on each of the common Jeep transmissions, including how to identify them.

When filling your T-150 with gear oil, we recommend that you select a conventional mineral oil or a para-synthetic in lieu of a full synthetic oil. Properly assembled manual gearboxes do not have the thermal strains seen by combustion engines or hypoid gears. Synthetic fluid in these gearboxes, while not harmful, is probably an economic waste.

Hypoid gear oil is sulphurized higher than Transmission oil and can be mildly corrosive to the non-ferrous alloys used for synchros, bushings and thrust washers in these transmissions.

An 80W-90, API-GL5 or MT-1 rated fluid is very good. Some claim faster shifts from using a 50W engine oil in their Transmission and we do not consider this to be contraindicated unless you operate your vehicle in a very warm environment.

 

[beltman]

Yes I read that whole page and thats where I get confused. I thought GL5 is bad for brass and copper? I can find GL 4 but in 85W90. Or Mobil 1 in 75W90. But thats a full syn. The only bad thing I have read about the Mobil is cost.