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mjeep01

Stiff Clutch Pedal After AX-15 Transmission Replacement on 1997 Jeep TJ Wrangler

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Hi,

  Just swapped out my AX15 transmission on my 97 Jeep Wrangler. After I completed the job, with the engine off, I was able to shift through the gears without issue. I pressed the clutch pedal and it was easy the first few times then became extremely stiff. I removed the external slave cylinder from the bell housing and manually pushed in the clutch fork with my finger. The fork moved forward easily, then I heard something fall inside the bell housing. I pulled the tranny back off and found the clutch fork retaining clip had fallen off. I proceeded to put it back in place ensuring it was secured. After attaching the tranny back on, I tested the clutch pedal which appeared to operate normally (engine off) as well as ensuring I could shift through the gears without issue. I then continued with attaching the rest of the harnesses, transfer case, etc.. I fired up the engine and heard a knocking sound which appeared to be coming from the external slave cylinder area. As I depressed the clutch, the knocking stopped. I turned off the engine, removed the slave cylinder and had my wife press on the clutch pedal. It became stiff again. I pulled the transmission again and the clutch fork retaining clip was still secured. This is where I have left off for the night. I plan on bleeding the master / slave cylinder system tomorrow and see if that fixes the issue with the stiff clutch pedal. Some questions:

 

1) How far should I be able to press in the clutch fork manually with the external slave cylinder removed from the bell housing?

2) Should the clutch fork return after being depressed manually (like a spring) with the external slave cylinder removed from the bell housing (mine didn't. After pressing on the clutch fork, it remained in the position I had pushed it to).

2) Should the clutch pedal move freely with the external slave cylinder removed from the bell housing?

3) Could it be the throw-out bearing? It appears to be ok from visual inspection, it slides along the transmission shaft easily, the springs are all intact. 

 

Any suggestions would be welcomed.

Thanks.

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Hi, mjeep01...This sounds like a loose or misaligned clutch release bearing.  Did you change the clutch and release bearing at the same time?  If you changed the clutch release bearing, did you install a new bearing with collar?  This sounds like a loose release bearing and collar.

 

Is the AX15 new or used?  Does the front bearing retainer (which supports the release bearing collar) match your original transmission?  Describe where you got the transmission and its original application.  Pre-TJ era AX15 transmissions do not have the same front bearing retainer.  They use an internal hydraulic clutch release bearing, not like your TJ's cross arm and external slave cylinder.  You need the release bearing sleeve, which is part of the TJ era AX15 front bearing retainer casting.

 

A binding slave cylinder would be most unusual.  The clutch master cylinder simply pushes hydraulic brake fluid into the slave, and the slave has an apply piston that should retract when the clutch pedal releases.  You can test the stroke and movement of the clutch release pushrod.  The pushrod should move freely under apply pressure and retract with the clutch pedal released.  Since you've been testing the slave out of the bellhousing, consider bleeding the clutch slave (while installed and fastened to the bellhousing).  If the system has remained closed and sealed, bleeding should not be necessary, especially if the pushrod moves normally and over its full range of travel.

 

Let's start here...Glad to comment further...

 

Moses

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Hi, thanks for replying. The transmission was from a 1998 Wrangler TJ I got from a private party. I've attached how the bearing / fork is put on the transmission input shaft. Let me know if it appears ok or not. The retaining clips are intact. I did not replace the bearing as the old one appeared ok. I've attached some photos

 

Thanks.

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post-634-0-39257300-1438886759_thumb.jpg

post-634-0-61686700-1438886760_thumb.jpg

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Update ***. I manually bled the slave cylinder by pointing the piston down and pushing the rod in about 20 times. No air bubbles were detected in the clutch master cylinder. I then pressed the clutch pedal and it went all the way to the floor once and came back up. I then tried to press the clutch pedal again and it was stiff again. Did this twice. Thinking it might be the hydraulic system. Anything else it might be?

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mjeep01...At this point, it looks like the parts orientation is correct...If the release bearing collar's inside bore is not matching with the diameter of the transmission front bearing retainer sleeve, the release bearing collar can bind on the sleeve.  If it's binding, this may not show up until the release arm is under tension from the clutch cover fingers. 

 

Check the side movement of the release bearing on the transmission front bearing retainer sleeve.  Check the sleeve for galling or wear.  Any roughness could "catch" the bearing collar, especially under tension, and bind up the arm and release bearing assembly.  The design is traditional and primitive.  There is always some friction between the release bearing collar and the transmission front bearing retainer's sleeve.  If there is too much slop or a rough area that can catch the collar, the release bearing/collar will bind.

 

Also check the height of the clutch cover's fingers with the transmission out.  They should stand out equally from the clutch centerline.  (If you have a clutch disc aligning tool, stick it through the disc splines and into the crankshaft pilot bearing bore...Use the tool for a reference point.)  If clutch cover fingers are not parallel to the flywheel (bad disc, something stuck between the disc and flywheel, a damaged clutch cover, etc.), the release bearing collar can cock and bind.

 

The release bearing collar should slide freely on the transmission's front bearing retainer sleeve, not rock much if at all, and not feel notchy or catch...

 

Moses

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Yep. The bearing appears to slide in / out without binding. The sleeve appears smooth as well as the inside of the bearing. the clutch assembly fingers appear uniform, parallel and undamaged. I think if I get this master/slave cylinder issue resolved, I may be home free (wishful thinking). I still don't know if the master/slave hydraulic system is good or not. I'm leaning towards not based on my description earlier in the thread but I wanted to see if anyone could confirm that or tell me if there is some other method of verifying it's bad before I go out and spend some money on replacing it.

Thanks again for responding.

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I re-read your post on bleeding the hydraulic clutch slave...The hard pedal sounds like fluid does not retract back into the clutch master cylinder.  When you get a "hard" pedal, the clutch master cylinder is stacking fluid into the slave and pushing the slave piston to the bottom of its bore.  Fluid should retract to the clutch master cylinder with moderate pressure on the end of the slave pushrod.

 

This is a "self-adjusting" clutch.  Fluid finds its own level when the clutch pedal is released.  This allows for the normal wear on the clutch disk, which will raise the clutch cover fingers as the disk gets thinner.  The release bearing throws back from the clutch cover release fingers each time the pedal gets released.  This places slight clearance between the release bearing's face and the fingers.  That space is required to prevent the release bearing from spinning continuously.

 

Likely fluid is not retracting back into the clutch master cylinder reservoir properly.  This can be caused by one of two things:  1) the port between the reservoir and cylinder bore is clogged, or 2) the clutch pedal is not adjusted for adequate free-play with the pedal released.  The clutch master cylinder pushrod must retract far enough to expose the port into the reservoir.  If not, the fluid will stay trapped in the system (slave cylinder) and stack up as you continue to pump the clutch pedal.

 

Pedal released, check for slight clutch pedal pushrod clearance at the clutch master cylinder.  Watch the fluid retract into the reservoir as the pedal releases.  This step will likely involve your wife.

 

Moses

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Ok...figured out the stiff clutch pedal. Bad master/slave cylinder. I replaced it and now have a functioning clutch pedal! Now for the bad news. After reinstalling the transmission (lost count how many times I did this...4, 5 times I'm guessing), I tried to fire up the engine...nada. I did some research and found a way to bypass the clutch interlock switch (had to disconnect the switch harness and connect the end of the harness that was not connected to the switch to another harness located nearby) and the engine fired up. On a side note, I tested the clutch interlock switch for continuity and it tested good but I will address that later. Once the engine was running with the clutch pedal depressed, it sounded good until I released the clutch...tap tap tap tap. I replaced the throw out beforehand but that made no difference. I pulled the transmission out again and started monkeying around by moving stuff in the transmission bell housing area. I discovered that the transmission was making the tapping sound when I rotated the input shaft by hand. The noise was muted as I was turning the input shaft by hand instead of the clutch/flywheel turning it but it sounded the same. I suspect that when the clutch pedal is depressed, the transmisison input shaft isn't turning because the clutch disc is detached from the flywheel but as soon as I let my foot off the clutch pedal, the clutch presses against the flywheel with turns the clutch and the input shaft of the transmission, making the tapping noise. I am now currently in contact with the seller of the transmisison for a refund/replacement. I'll post follow ups as I get them. Thanks for you assistance.

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One question...the seller was indicating I should be using 10w30 instead of 75w90 (specified in the FSM). I've read other posts where 10w30 has been used but wanted your opinion. Regardless of which oil, the transmission should not be making any tapping noise if rotating by hand right?

Thanks.

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Tapping noises from within a transmission are not a good sign, anytime.  I would use 75W-90 as originally specified.  At the AX15 forum topics, we discuss oil/lube at length.  The new replacement for Mopar 75W-90 GL is supposedly 10W-30.  I'm not in favor of motor oils in a transmission.  Transmissions require an EP (extreme pressure) lubricant.  Engine oil is not.

 

There was a Mopar AX5/AX15 specified oil that I used until at least a decade ago.  Toyota recommends GL-4 gear lube in its rendition of the AX15.  I stick with gear lube.  The deal breaker is when synchronizer braking action will not take place. 

 

Valvoline recommends its MTF oil, an EP gear lube replacement for the original Chrysler lube designed for the AX5/AX15.  Here is my currently and affordable choice:

 

General Motors & Chrysler:

Valvoline Synchromesh Manual Transmission Fluid

 

• High performance manual Transmission lubricant

designed to meet the extreme demands of passenger

car manual Transmission gearbox applications

• Enhanced performance in both low and high

temperature operating conditions

• Excellent wear protection under high loads and

extreme pressure

• Resistance to oxidation and remains stable under

extreme pressures

• Exceptional anti-foam performance for added protection

• Recommended for General Motors and Chrysler vehicles

including GM part numbers 12345349, 12377916 and

12345577 as well as Chrysler part number 4874464

Part# 811095

 

Was your original transmission rebuildable?  Is this one?  Do you want to rebuild the unit?  Many have done so successfully by following my Vimeo On Demand AX15 rebuild how-to video.  See the trailer at:  www.vimeo.com/ondemand/ax15rebuild.

 

Moses

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