T-90 Transmission

The stock transmission during the 20 years of production of the Willys Jeep Utility vehicles was the Borg-Warner T-90 3-speed transmission. The gear ratios are on the Gears page.

First and reverse are not synchronized. Second and third are synchonized. The shift pattern is and 'H' with reverse upper left, 1st lower left, 2nd upper right and 3rd lower right.

You should make sure that your transmission has adequate gear oil. There are two plugs in the side of the case. The lower one is to drain the old oil out. The upper one is to fill the case with new oil. You will need a pump to squirt oil up into the case from underneath. It can be filled from the top if the shift tower is off, but removing the shift tower is a lot of work just to add some oil. You can get a plastic pump that screws onto the top of the gear oil jug. 80W90 gear oil is the standard. (Some people use 90W140 for more protection in hot tempertatures.) This is the same oil that you should be using in the transfer case and the differeentials.

I have taken the T-90 on my pickup and the T-90 on my wagon a part. I won't try to describe the whole process. My internet friend Rick Stivers has done a better job than I could. Take a look at his T-90 Rebuilding Guide.

If you are having trouble shifting into second or third without grinding, it is probably because the brass synchonizer rings are worn. If you take your transmission a part for any reason, it is advisable to replace these unless you know they have been recently replaced. It is difficult or impossible to see the wear on the syncho rings.

When you service you transmission, you can get a "small parts kit" which includes the free rollers for the bearings, thrust washers, lock plate for the shafts, and felt seal for the input shaft.

Off-road also has some information at Jeep Transmissions: T-90.

© Richard B. Grover 1997 to 2006. Last updated: Friday, October 13, 2000