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AX-15 Gear Engagement Problem

D

DickDC

NAXJA Forum User
Location
Lansing,MI
I have a 1996 JX 2dr 2wd with an AX-15 tranny. I've owned it for 11months and have had engagement problems since the beginning. I have a mechanic that has been working on it, rebuilt clutch , new flywheel, pressure plate, throwout bearing. It still was very hard toget into gear.
Next I tried to by a rebuilt tranny from a company I found on the internet that had good pricing. They advertised that they were in Minn. iirc , but were actually in Texas and an on-line store front for a bigger rebuild company. They sent (Honestly) 3 different tranny's and 1 twice. Four times total. None were the correct one. A couple were easy to tell but one was just splined different and couldn't tell until it was installed. After a couple months dealing with them my mechanic says he has a guy who will rebuild it.
Flash to now, as the XJ heats up driving around town it gets harder to put in gear while upshifting or downshifting until I can't get into gear (except 3 or 4 sometimes) at all. After shuting off the engine I can put it into gear without the clutch.
So far I've been met with skepticisim from the guy who built the clutch and my mechanic.
Has anyone got a good guess as to what the hell is going on with my XJ? It's been expensive so far and can't afford to keep chasing ghosts.
Thanks
Dick--
 
I was told synthetic oil after "rebuild?".
There was some problem bleeding the clutch. Not sure if it is correct.
It seemed tonight like the longer I drove around town it kept getting worse. I just picked it up today because it did it last time I drove and I had it towed to the mechanic. He bled it and thought the clutch felt good. I did also when I started running errands.
Thank for any help.
--Dick---
 
I would definetly change the tranny fluid, if the fluid in the AX-15 gets old they get real hard to shift, your exact symptoms describe old tranny fluid. Jeep uses and recommends 75W-90 synthetic oil for the AX-15, its about $12 a qt. I am about to put AMSOIL 75W-90 manual transmission & transaxle gear lube and see how it does compared to the factory synthetic.
the clutch can be a pain to bleed sometimes, usually they will work the air out of the lines by just driving it though. The first one i did we bleed it for 30min and it still didn't do to well until i drove for a while.
 
I used Redline MT 90 in mine.

Can you get it to shift normally if you double clutch it? Maybe the rebuilder didnt get the synchros right?
 
what ever you do, do not use a gl5 gear oil in the ax-15


if you cant find a gl3 or a yellow metal friendly manual trans fluid, 10w-30 synthetic motor oil is fine to use and many actually prefer the motor oil.
 
souske said:
I used Redline MT 90 in mine.

Can you get it to shift normally if you double clutch it? Maybe the rebuilder didnt get the synchros right?
Click to expand...

the redline is worth every penny they charge.
it basically
"fixed"
my 1st to second shift problems.
make sure it has the right fluid in it. They're very picky.
I know that toyota recommended 30W oil in basically the same trans, but I've never tried it.

You may also want to pull the shifter out of it and make sure that it still has the nylon(?) bushing. If that's missing you won't get full throw on the shift rails from the shifter. Pop off the shifter boot and it's just 4 bolts to take off the whole tower. To remove just the shifter, push down on the stamped "cup" and rotate it about 1/8 turn to the right (IIRC) it will pop up. Be careful, as that spring in there is pretty stout. From there you can pull just the shifter and not the whole assembly, check out the ball area, and make sure that bushing is down in te receptacle it goes into.
This is also the easiest way to get new fluid in, rather than pumping oil into it from underneath.
 
try bleeding your clutch. have you replaced the slave and master cylinder
 
Definitely make sure you have the right fluid--gen-u-ine GL-3; Redline MTL 90; Pennzoil Synchromesh; gen-u-ine Mopar synthetic ($22 quart); any good quality 10w30 synthetic motor oil--MUST BE YELLOW METAL SAFE.

You said "new flywheel"--sure about that? Per FSM if the flywheel requires resurfacing it is to be replaced. However, some post on here that they have had theirs resurfaced without any problems, but others have had disengagement problems after resurfacing the flywheel. Some have corrected the problem by using aftermarket MC with larger diameter pistons like the Howe racing MCs.

Good luck.
 
Your problem sounds like you need to dump the fluid in it, and swap it with synthetic 10w-30 engine oil. Trust me on this.

Also, and most importantly!!!!! LOOK INTO YOUR SLAVE CYLINDER setup. This is where i believe your problems are coming from. If this is the problem your jeep will act as if you aren't pushing your clutch all the way to the floor. leading to grinding entering reverse and stiff engaugement in all gears.
 
Wanted to update you on where I'm at with this problem.
First to answer some of the questions. The flywheel is new. It, along with a Hurst shifter (both from Summit) were the first things I bought for my XJ. I thought it needed a clutch when I bought it and wanted to add a lighter weight flywheel. It did not seem to be lighter. I would still like to find a lighter flywheel that is streetable.
Over last winter I had a mechanic do the cluth, flywheel, etc. . He had a clutch built locally and said he did replace the throwout berrings. He also had the tranny rebuilt locally. The syncros seem a little stiff though.
For some reason he made a shorter rod (outside the trans.) that engages the clutch.
As it heats up and everything clutch related expands, the rod becomes too short. He shimmed it .015 longer today while it was hot and refusing to allow the shift lever to go into gear. I guess it actually wasn't letting the clutch completely engage or disengage. Don't know which. The shimming now allows me to get into gear fairly normally. He said drive it and when the shimming seems correct he will make a new rod. Time will tell more.
The mechanic said he put synthetic oil as recommended in the tranny after the installation.
There was some bleedind problems after he put a new slave cylinder in about 12 days ago. The air seems to be out of the system finally!
Also double clutching never helped. The only way I could get it into first gear when hot is to turn the engine off and the shift.
The tranny feels a bit slow and stiff when I move the shift lever. Not sure why but the idea of a thinner oil sounds like an interesting idea. Posters here have given several different weights to use. Any more recomendations or sources for ideas on oil weight would be appreciated.
So, I need to drive it around for a couple days to see about the shimming.
Would like info on a light weight flywheel for my 4.0 L . Would it be the same flywheel on a 258 crank if I build a stroker.
Where has it been said I could go from 90wt. to 30 wt. Tranny fluid
THANKS
 
Wanted to update you on where I'm at with this problem.
First to answer some of the questions. The flywheel is new. It, along with a Hurst shifter (both from Summit) were the first things I bought for my XJ. I thought it needed a clutch when I bought it and wanted to add a lighter weight flywheel. It did not seem to be lighter. I would still like to find a lighter flywheel that is streetable.
Over last winter I had a mechanic do the cluth, flywheel, etc. . He had a clutch built locally and said he did replace the throwout berrings. He also had the tranny rebuilt locally. The syncros seem a little stiff though.
For some reason he made a shorter rod (outside the trans.) that engages the clutch.
As it heats up and everything clutch related expands, the rod becomes too short. He shimmed it .015 longer today while it was hot and refusing to allow the shift lever to go into gear. I guess it actually wasn't letting the clutch completely engage or disengage. Don't know which. The shimming now allows me to get into gear fairly normally. He said drive it and when the shimming seems correct he will make a new rod. Time will tell more.
The mechanic said he put synthetic oil as recommended in the tranny after the installation.
There was some bleedind problems after he put a new slave cylinder in about 12 days ago. The air seems to be out of the system finally!
Also double clutching never helped. The only way I could get it into first gear when hot is to turn the engine off and the shift.
The tranny feels a bit slow and stiff when I move the shift lever. Not sure why but the idea of a thinner oil sounds like an interesting idea. Posters here have given several different weights to use. Any more recomendations or sources for ideas on oil weight would be appreciated.
So, I need to drive it around for a couple days to see about the shimming.
Would like info on a light weight flywheel for my 4.0 L . Would it be the same flywheel on a 258 crank if I build a stroker.
Where has it been said I could go from 90wt. to 30 wt. Tranny fluid
THANKS
 
I think you need to look more carefully into the clutch linkage. Make sure that the linkage itself is not bent or damaged. There's a weak spot (poor weld) on the bracket that engages the MC rod, which can bend and cause poor clutch action as well as eating the master cylinder bore. You shouldn't need to shim or modify the rod if the pedal bracket is in the right place.

You need to find out if the clutch is disengaging properly before you dump much more into transmissions. The AX-15 tends to be a little stiff at times, but with the right oil and a clutch that lets go properly it should work all right without a lot of fuss, and a synchro problem should be helped by double clutching. On the other hand, I can testify from experience that this tranny is almost impossible to shift clutchless, even when up to speed in higher gears. So that's where I'd look for your problem.

The sealed hydraulic system can be tricky to bleed, since there's no bleeder hole. If you take the slave cylinder off the housing, and compress it all the way in, then fill the master cylinder, then pull the slave cylinder out as far as it can come without coming out of the bore, and repeat that process, it should bleed. But you must be very careful not to let the slave rod come out of the bore, or you may ruin the slave cylinder. The slave piston travels further in both directions when you do this than when it's installed. The trick here is to make the slave cylinder displace more fluid than the master and line combined.
 
DickDC said:
Wanted to update you on where I'm at with this problem.
First to answer some of the questions. The flywheel is new. It, along with a Hurst shifter (both from Summit) were the first things I bought for my XJ. I thought it needed a clutch when I bought it and wanted to add a lighter weight flywheel. It did not seem to be lighter. I would still like to find a lighter flywheel that is streetable.
Over last winter I had a mechanic do the cluth, flywheel, etc. . He had a clutch built locally and said he did replace the throwout berrings. He also had the tranny rebuilt locally. The syncros seem a little stiff though.
For some reason he made a shorter rod (outside the trans.) that engages the clutch.
As it heats up and everything clutch related expands, the rod becomes too short. He shimmed it .015 longer today while it was hot and refusing to allow the shift lever to go into gear. I guess it actually wasn't letting the clutch completely engage or disengage. Don't know which. The shimming now allows me to get into gear fairly normally. He said drive it and when the shimming seems correct he will make a new rod. Time will tell more.
The mechanic said he put synthetic oil as recommended in the tranny after the installation.
There was some bleedind problems after he put a new slave cylinder in about 12 days ago. The air seems to be out of the system finally!
Also double clutching never helped. The only way I could get it into first gear when hot is to turn the engine off and the shift.
The tranny feels a bit slow and stiff when I move the shift lever. Not sure why but the idea of a thinner oil sounds like an interesting idea. Posters here have given several different weights to use. Any more recomendations or sources for ideas on oil weight would be appreciated.
So, I need to drive it around for a couple days to see about the shimming.
Would like info on a light weight flywheel for my 4.0 L . Would it be the same flywheel on a 258 crank if I build a stroker.
Where has it been said I could go from 90wt. to 30 wt. Tranny fluid
THANKS
Click to expand...

Here is a link to the mt-90 http://www.summitracing.com/parts/RED-50304/
And a flywheel:http://www.summitracing.com/search/Year/1996/Make/JEEP/?keyword=fidanza
Its still billet steel though, no aluminum listed. Probably going to have a rough time with that one as most of us want a heavy flywheel for wheeling.

Any reason you cant use a new rod and call it a day?
 
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