Hard shifts in a AX15..

Jeep9748

TJ Enthusiast
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I imagine this has been discussed, but I am in need of help.. 97 4.0 AX15 219000 miles. So about two-three years ago, I changed the oil in my 5 speed. I used 10w-30 synthetic. This was great it shifted perfect. Well now I am having an issue with shifting. I have push extremely hard into first, and it will only go some of the time. I feel I am going to break the shifter if I push any harder. Second gear is the same way. There is no grinding unless I am attempting to stop and go into reverse. I am currently at the point where I have to turn the engine off shift then restart. Also the shifting is getting the same way in 3-5 gears. I am going to drain the fluid tonight and put 75w-90 in and see if that helps. If anyone else has had this problem, let me know what you discovered. Oh the clutch seems fine.
 
I had notchy shifting w my AX-15 w only 12k miles on it. I changed the fluid to Pennzoil Synchromesh, and it noticeably improved. But I can't say for sure if that'll cure any of your issues. I have been told to go w a Mopar Clutch kit to improve the shifts (sounds like hog) and that AX-15's are often noted as finicky / notchy shifting transmissions, especially in 1 & 2nd gear.

The only thing this trans did better than my NV3550 is run quietly.


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A Mopar clutch kit shouldn't shift any better than any properly working clutch. LUK is my go-to for clutches and they manufacture the OEM clutch anyways. They all work the same for shifting purposes.

Probably not the fluid either since motor oil is approved for the AX-15, and his problems seem pretty out of the blue. Fluid doesn't usually go bad all of the sudden and cause hard shifts. Although, I would definitely recommend Redline MT90 if any fluid change is to be done.

His exact symptoms are what has happened to me every time my master/slave cylinder combo has gone bad. It doesn't fully release the clutch so it's as if you're shifting while in gear.

My money is on the hydraulic assembly.
 
(Edit) as said above, start with master and slave you can order a sealed bled assembly off rockauto and is very easy to replace.

I had the same exact symptoms turned out being the throw out bearing, bearing itself was fine but the clips that hold it in had worn and broke off so my clutch was not completely disengaging. If this is the case don't drive like that too long or it will prematurely wear the syncros.
 
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I had the same exact symptoms turned out being the throw out bearing, bearing itself was fine but the clips that hold it in had worn and broke off so my clutch was not completely disengaging. If this is the case don't drive like that too long or it will prematurely wear the syncros.

This makes perfect sense. I think it's probably time to pull the transmission and inspect things @Jeep9748
 
Being that the hydraulic unit is removed as simply as 4 bolts/nuts and a retaining clip on the clutch pedal, I would do that before pulling the transmission for a throwout bearing that may or may not be broken. While that's a possibility, I would definitely try the easier route first.
 
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Well super, Guess I am gonna have to figure something out. Military budget says no to 142.99 on the slave cylinder. Really hoping to not pull the trans. Oh well guess I will have to find another way, time and money are against me as of late....
 
Park it and save up some money (if you can)?

Not sure where you're stationed, but when I was stationed at Fort Lewis (Army) I never needed a car, it was so easy to get around base without one.
 
The hard shift problem has long plagued the manual transmissions in the TJ, both the AX-15 and NV3550. My previous TJ's AX-15 often had big problems shifting into 1st gear. I dunno what the fix is, nothing easy really seems to provide an immediate fix. Mine still had that shifting issue after switching to Redline MT-90, installing a new pilot bearing, installing a new clutch and throw-out bearing, and verifying that the hydraulic mechanism was working properly and pushing the clutch mechanism all the way in as it should have. I didn't perform all those steps to fix the shifting issue, they were just normal maintenance items, but I was disappointed the shifting didn't improve after doing any of them.

Maybe there's a definite fix but I've yet to see it in all the many threads on this issue in the various Jeep forums I have been in over the past 20 years.
 
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So is it more likely the slave cylinder or the master cylinder? is one more prone than the other.
 
You need to buy the assembly together. Slave, master, line, all connected and pre-bled. Some setups don't even have a way to bleed, so purchasing parts separately won't work. The ones that do have the bleeders, are such a PITA to get bled correctly that it isn't even worth the time messing with it.

To answer your question, it's most likely the slave. I would still only buy the pre-bled kit.
 
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For what its worth, I went out on break and looked the entire system over. The master and slave are bone dry on the outside, meaning no evidence of a leak. Stupid question if the fluid is low, could that cause it to malfunction?
 
They don't have to leak necessarily. Neither of mine leaked anywhere, they just stopped being effective when I pushed the clutch.

Yes, not having enough fluid is a problem. However...if you're low on fluid, then it went somewhere and is a good sign that your hydraulic unit is faulty. I would try to get that money as quick as you can and get you an assembly.

Check a junk yard for one from any TJ. Surely you can get one somewhere. If you can't find junkyard, I would say try to find and purchase the Mopar original part. It'll make it another 219,000 compared to my O'Reilly junk parts that die every 1.5 years. I'm about to cave and buy a Mopar unit and keep the O'Reilly as a spare.
 
Yup! If everything is okay beside being able to get it into 1st gear then there is a clutch problem. So the clutch hooks up fine and it shifts fine in other gears ( thank you synchros) your problem sure seems to be in the linkage between your foot and the throw out bearing. So either save the $$ to replace parts, or do what I did and learn how to shift with rpm throttle management. No I am serious. I have been broke and lived thru it. Ya just have to adapt;)
 
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Well I made the worst drive getting home. Fairly certain it's the hydraulic setup. Left work and it was a horrific drive. Pushed clutch pedal to floor and couldn't get any gear to engage. If I did get it in gear would have to hold brake or it would keep going as if still engaged. Clutch is strong as at some points I only had third gear engaged and would have to start or stop in that. When I stopped at stop signs with it in third gear, brake held to keep from rolling on, engine rpms would be up around 1200. So I guess I am gonna be in the wife's minivan until I get the new master slave cylinder kit.