Unusual AX-15 Problem

D

Dirty4LetterWord

NAXJA Forum User
Location
AZ/SC
Unusual AX-15 problem

Newbie here! I know it's not an XJ, but I have a 94 YJ with an AX-15 5 spd tranny. I have posted on another Jeep forum, but am hoping for some help from the experts here, as well!

I recently installed a new Luk clutch (about a month ago), which has been working fine so far. Within the last week, I began to experience a lot of gear rake when shifting into fourth gear, along with the already-present 2nd gear rake that came with the Jeep. We pulled the Jeep into the garage, put it in neutral, and as soon as I let up on the clutch, the Jeep started creeping forward and makes a pretty loud clicking sound, like a gear is still partially engaged. It also sort of lurches when in reverse, like it wants to go forward as well as backward. All fluids are full. Clutch pedal feels fine and shifts into each gear, although it did try to lock in reverse once. Synchronizers? Broken fork? Tranny problem at all, or something else? I would appreciate any help I can get - does the factory service manual have much AX-15 tranny info?

THANKS FOR ANY SUGGESTIONS!!
 
Re: Unusual AX-15 problem

It certainly does sound like an internal problem. The only clutch-related problem I could picture off the top of my head would be if something wrong in the installation put so much end load on the input shaft that it was causing the interface between the input and output shafts to bind. The input and output shafts are on the same plane, appearing as the same shaft, except with a bearing in the middle to allow them to rotate independently. If there were enough end play in the input shaft, and enough pressure on it, it could cause the input shaft to try to rotate the output shaft even when it's in neutral.

Assuming that that's not the case, though, I'd guess that there's a problem inside the tranny. Fortunately, the FSM does have the full repair information.
 
Re: Unusual AX-15 problem

Dirty4LetterWord said:
Newbie here! I know it's not an XJ, but I have a 94 YJ with an AX-15 5 spd tranny. I have posted on another Jeep forum, but am hoping for some help from the experts here, as well!

I recently installed a new Luk clutch (about a month ago), which has been working fine so far. Within the last week, I began to experience a lot of gear rake when shifting into fourth gear, along with the already-present 2nd gear rake that came with the Jeep. We pulled the Jeep into the garage, put it in neutral, and as soon as I let up on the clutch, the Jeep started creeping forward and makes a pretty loud clicking sound, like a gear is still partially engaged. It also sort of lurches when in reverse, like it wants to go forward as well as backward. All fluids are full. Clutch pedal feels fine and shifts into each gear, although it did try to lock in reverse once. Synchronizers? Broken fork? Tranny problem at all, or something else? I would appreciate any help I can get - does the factory service manual have much AX-15 tranny info?

THANKS FOR ANY SUGGESTIONS!!
Click to expand...

You can rebuild an AX-15 with an FSM, provided you have the tools.

Dumb question - have you tried bleeding your slave cylinder? I'm not sure if the YJ came with an "internal" slave or not (damn bad idea from the off, I'm tired of changing mine at $110 a pop...) but I've got a failing slave/throwout that causes similar symptoms - most notably the wanting to move while the clutch is in and the transmission in gear (since it's damn near impossible to shift into first when sitting still, I end up getting smoke. Should get that fixed this week - since I've got just about everything else tied up for the moment...)

Oh - and I moved this to "other" tech - you may get a better response there. I know this is an OEM problem for you, but it's still not an OEM XJ problem - and some mental gear-shifting is usually required (for instance, I'd not be surprised to find that you have the more useful external slave, vice that "internal slave cylinder" abortion we were stuck with until 1995/1996 or so...)

5-90
 
Matthew: That was another possibility we had just today considered, and hopefully between jobs and sleep will know for sure in a day or so. Believe me, I prefer it to be a clutch problem, but I have a feeling it's not, or only partially.

5-90: I do have an external slave. When we installed the clutch, we re-used the old slave because it seemed to be working fine, (although I do have the new one), but did put in the new throwout bearing. But, no, I have not bled any part of the hydraulic system or replaced any fluids other than the gear oil. It has yet to try to move while the clutch is pressed to the floor, but with the clutch pedal released and the shifter in neutral, it creeps.

Thanks for both of the suggestions and the help!!

Dirty4
 
Dirty4LetterWord said:
Matthew: That was another possibility we had just today considered, and hopefully between jobs and sleep will know for sure in a day or so. Believe me, I prefer it to be a clutch problem, but I have a feeling it's not, or only partially.

5-90: I do have an external slave. When we installed the clutch, we re-used the old slave because it seemed to be working fine, (although I do have the new one), but did put in the new throwout bearing. But, no, I have not bled any part of the hydraulic system or replaced any fluids other than the gear oil. It has yet to try to move while the clutch is pressed to the floor, but with the clutch pedal released and the shifter in neutral, it creeps.

Thanks for both of the suggestions and the help!!

Dirty4
Click to expand...

Interesting. If it's trying to crawl in Neutral, then maybe it's not quite in neutral?

5-90
 
5-90: Exactly, at least that's what it acts like. Somehow a gear's not completely disengaging. I just talked to a mechanic who just happened to walk into my shop a few minutes ago, and he also suggested the air-in-hydraulic-line scenario, but he also said it could be meshed synchros or something melted to something else in the tranny. Guess I'll start with the hydraulics, and go from there. It may be a day or so, but I'll be back soon! If you come up with anything else, let me know. I'll probably have my nose stuck in the FSM!

Thanks, guys!

Dirty4
__________________
DirtyJeep? DirtyGirl?
 
If it were a clutch problem, you'd have trouble going into gear - especially when sitting at idle (it would be easier with the vehicle in motion.)

I haven't torn apart an AX-15 yet, so I don't know the internal arrangement as well as I'd like to, but does it make any noise when it's trying to crawl on you?

5-90
 
No problem shifting into any gear at idle, but with the clutch pedal released and the shifter in neutral, it makes a pretty loud & fast clicking noise, like maybe the edge or teeth of a gear? Also, I put it in neutral (without ignition), got out of the Jeep, we pushed it about 4 or 5 feet forward, the same distance backward, started it. When it first started, there was no noise or creep in neutral, but once the clutch had been pressed and the shifter moved into any gear and back into neutral, the noise and creep returned. (I'm reasonably sure the creep is not just from vibration, it's a pretty good crawl.) And, when I put it in reverse and let out the clutch, it feels and sounds as if there is some kind of resistance and the Jeep sort of lurches a little bit, like something else is catching, almost like it is trying to go forward as well as backward (I know that sounds weird, but that's what it feels like.) I ordered a(n) FSM today, hopefully I'll have it before the weekend. I'm pretty curious about those tranny guts, myself! I found a parts diagram, but it's not really a good exploded view that shows what goes where.

But, I am wondering about the clutch hydraulics. Every manual, catalog & tech site I've read claims that I should have an internal slave & sealed system. I've already replaced the clutch MC twice, and have obviously ordered a slave by itself separate from the whole system, and can check & replace fluid in the clutch MC. And the dealership told me I could not order the hydraulic line by itself, had to order the whole sealed system. Could it be that my system is not stock? Or did they change it mid-year? (Just thinking out loud!)

I'll know more tomorrow!

Dirty4
__________________
DirtyJeep? DirtyGirl?
 
OK, I'm back! Over the weekend we finally got the tranny out. Clutch looks fine. We put the shifter in the tranny and went through all gears, all seems nice & smooth inside the tranny. All gears engage & disengage, and shifter feels smooth in neutral. Input & output shafts both move like they're supposed to. Now I'm leaning toward hydraulic issues. We're going to clean everything back up, reinstall, and stroke the slave cylinder to see if that helps. Cross your fingers for me, I MISS MY JEEP! Thanks a bunch for the assistance!!

Dirty4
___________________
DirtyJeep? Dirty Girl?
 
Do you have the proper lubricant in the tranny??????
 
I've been using what the owner's manual calls for - 75w-90 gear lube. Could you recommend something else that may be better? I've seen on some posts where some people have been using a couple of other brands, but hadn't really paid much attention to what they were because I wasn't having any problems at that time.

We haven't cracked open the case, and had kind of decided not to because everything seemed so smooth once we had it out of the Jeep. What did you find was the problem with your synchros, just so I know what I need to look for?

Thanks!
Dirty4
___________________
DirtyJeep? Dirty Girl?
 
Dirty4LetterWord said:
We haven't cracked open the case, and had kind of decided not to because everything seemed so smooth once we had it out of the Jeep. What did you find was the problem with your synchros, just so I know what I need to look for?
Click to expand...
Its been 10 years since I was in that transmission but I "think" the problem was they were worn down and the didn't fit over the cone of the gears right. They would go down too far and stick them selfs to the cone.

As far as additive....The place we bought parts from told us of an additive you should run in them. Now I can't remember what it was called.

You might want to call a professional tranny parts house and ask them.
 
I had the same problem, I had a small air bubble in the hydraulic line. I don't recomend additives as they mostly cover the problem, not cure it. If you have synchro problems, get them cleared up while the tranny is out. They aren't that hard to change, and IMO worthwhile doing. I redid mine, and at the same time, put in new seals, and it was happier, but I was frustrated by the air pocket, and was going to rip out the tranny, when a friends suggested we rebleed the slave, and after that it has been no problem.

Dirty4LetterWord said:
I've been using what the owner's manual calls for - 75w-90 gear lube. Could you recommend something else that may be better? I've seen on some posts where some people have been using a couple of other brands, but hadn't really paid much attention to what they were because I wasn't having any problems at that time.

We haven't cracked open the case, and had kind of decided not to because everything seemed so smooth once we had it out of the Jeep. What did you find was the problem with your synchros, just so I know what I need to look for?

Thanks!
Dirty4
___________________
DirtyJeep? Dirty Girl?
Click to expand...
 
I'm pretty sure there was something going on with the synchros, but I think possibly also hydraulics. We pulled out the gears this weekend, and when we drained the fluid, there was quite a bit of ground synchro material in the fluid. Unfortunately, we didn't pay close enough attention to the fluid when we redid the clutch in Nov., so I don't know if this has been an ongoing problem, or if it was the result of something we did when we installed the new clutch. I found a bearing/seal rebuild kit w/synchros for about $145 (thought I was gonna have to pay $400!), so I think I'll try that, plus installing the new slave cylinder that I probably should have installed in the first place. I don't have the gears torn apart yet, but I can't really tell where or which synchros are shedding all the material, because I have nothing to compare it to.

Dirty4
__________________
DirtyJeep? DirtyGirl?
 
Usually when synchros go, you can see visually when you get to the gears, which ones have been worn down, especially if you have lots of discoball juice coming out.
 
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