AX-15 acting weird

Miles Maheu

New Member
Joined
Oct 27, 2019
Messages
5
Location
United States - Missouri
So I have a 2000 tj with an ax-15. I know doesn’t make sense lol. As nv3500 or 3550 can’t remember which it is that comes stock in my tj is extremely expensive to rebuild for a 1/4 ton truck transmission when it went out last year I swapped an ax-15 out of a yj into my tj. It had an unknown number of miles on it as it had probably been in different Jeeps. Made some noises but just sounded like bearings that were old. One day not sure if I hit a bump or something but I was cruising in neutral getting off the highway and the transmission started making a light grinding sound almost as if I was trying to put it in gear without the clutch but it was in neutral. It wouldn’t allow me to go into gear either. Then it stopped and acted fine. The next day was on my way to work and felt it do the same thing so I took it home and parked it. I need to check the fluid but I just did a fluid change in it because it was leaking and wanted to add some stop leak. I didn’t notice a leak after the fact but am going to check the fluid this weekend regardless and try adding more to see if that helps. If anyone has had this problem before or has any insight on what it is some knowledge on the issue would be much appreciated.
 
If you run low on fluid they can be harder to shift. Mine was getting to the point where it was very difficult to get into gear but a fluid change seemed to solve that. I wouldn't add stop leak or anything other than GL4 gear oil. GL5 will just mess up the synchro's. If you have a leak you're best bet it is get some gasket maker, pop the housings off and make a new seal.

I ended up buying a re-build kit for a few hundred and I spent a day or two tearing it down and rebuilding it because mine was making a lot of noise in 2nd gear. I ended up finding a broken reverse idler gear, and a damaged 1-2 slider sleeve. I took my time, followed the FSM and a good video on YouTube and ended up with a good rebuild in the end. They're really not that complex.

As for the grinding noise in neutral, I'm really not sure. I can't see a way mechanically that any of the slider sleeves would be partially engaged onto the synchro, or even how the reverser arm could engage the reverse idler while the shift forks were all in neutral and then just go away. Its possible you have a chip in there and maybe it just got carried up into the gears and then washed away by the oil?
 
Adding a stop leak to your transmission lube was a mistake, no telling what it did to your synchros. I'd at least try a drain and refill it with the correct gear lube like a synthetic 10W-30 engine oil (yes, per the transmission manufacturer) or Redline MT-90. Both of those lubes have essentially the same actual viscosity.