1046545
I just replaced the transmission in my 93 YJ 4.0, the 4.0 has an AX-15 transmission. The NP231 is the transfer case. I replaced it with an AX-15 from a 91 cherokee, slight input shaft difference, had to make fabricated parts for it, nothing tough... back to the topic here. After replacing it... obviously I had to fill it. Because the AX-15 is only a medium grade transmission, it cannot always handle the torque produced by the 4.0L muscleshack(not quite). One problem with these is that the synchronizer in 2nd gear starts to go bad.. then 3rd gear... and so on(not always this order)... When they go bad, you begin to grind all the time, and that eventually will shake your bearings loose. This is what happened to my transmission... Why does this matter to you??? Here is the answer... I read on several other Jeep boards, that there is a way to prevent/resolve this. If you step up the thickness in your gear oil, it can act as a helper to get the synchronizers spinning when they need to. Its a little tougher on the motor when the transmission is cold, and just starting on cold days... but once its warmed up... you get a good smooth shift. An alternative to this would be to get some GM Synchro-Meshing Fluid... This also has agents that protect your synchros and help them to keep your gears in sync with each other when shifting. I went with the thicker oil myself, due to cost reasons, but if I had the money.... The GM S-M fluid is the way to go.... My transmission took 3 1/3 quarts of oil to fill it... It is a pain in the balls to do it, because of the thick nature of gear oil. So I suggest warming it up a little to loosen it up before putting it in. The easiest way to guess how much you will need would be to buy 4 quarts, and fill it until it starts to run out of the fill hole. Check your axle oil levels... if you are low, then use the rest of what you had from the transmission to bring the axle level back up. Let us know how she turns out.[addsig]
