YJ/NP231 NIGHTMARE! HELP!

boostaddict

boostaddict

Active Member
Joined
Jan 29, 2008
Location
Greensboro
Sorry for being dramatic but this thing is driving me nuts!

Problem: no power transfer from tranny to t-case

89 YJ

original 4cyl swapped to 93 4.0L (if it matters)

NP "231 J" is what t-case tag reads (this t-case has recently been installed)

No matter what position I shift the t-case into the Jeep does not move. I can put it in 4H or 4L and turn the front driveshaft and the rear turns and when I put it in N or 2H I can spin the rear driveshaft (rear axle is on jackstands).

I pull the t-case, flop it out in the floor it works FINE! I run through the gears on a few times, it's FINE!

I check the tranny output shaft, it's spinning when in gear and engine running and won't move when I shut the engine off like it's supposed to.

So I decide to throw the t-case back in. I leave it in 2H and sit it in, then I go ahead and stick the rear driveshaft in and check to make sure it is locked like it should be (tranny in gear, engine off). THEN I tighten up the t-case bolts and pull it all together snug. PROBLEM RETURNS!!!! No power transfer from tranny to t-case but all other t-case functions are fine.

Am I missing something???? THANKS IN ADVANCE!!!
 
Yep. Just what Lee said. What transmission are you running? I know personally that a 21 spline output will fit inside a 23 spline input w/o engaging the splines.
 
That makes about as much sense as anything......I checked the OD of the tail shaft with a cheap little caliper I had and it was so close to the ID of the tcase shaft I just assumed it was correct, didn't count the splines though. I will do that next. THANKS!!!
 
Idk what tranny is in it, my YJ tech is slackin.....it's the original 4cyl 5spd but the Jeep has not moved since this tcase was installed. I trailered it to my shop.
 
The AX5 4 cyl tranny is a 21 spline output. Did you somehow adapt the 4.0 to an AX5 (4 cyl) tranny? If so, you'll need a 21 spline input for the t case.
 
Early AX15s are 21spl, too.
 
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