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Discussion Starter · #1 ·
Hi Forum,

I'm at a loss with what to do next on my TJ and need some help. It is a 1999 4.0L with an AX15. 123,000 miles.

Sorry for the long post. This has been a year in the making. I've googled and read extensively and have exhausted every option/solution I know of short of replacing the transmission. I want to make sure that is my only next step before I pull the trigger.

A while back I drove it through high water, I didn't get stuck, but it was to the door handles and I got out very slowly. Shortly after, I started having a slight grind into 3rd only when the jeep was warm. If I let the RPMs come all of the way down before shifting into 3rd, it wouldn't grind most times.

I changed out the tranny fluid to 10w30, ran it for 1,000 miles, then switched to Syncromesh. Didn't fix the issue.

It started grinding into 5th too, every time. No amount of RPM matching, slow shifting, or double clutching will resolve this.

Then I noticed that it wouldn't roll backwards on an incline when in 1st with the clutch fully depressed. And wouldn't roll forward in reverse the same. It will roll backwards when in 3rd to 5th gear though. It won't shift into 1st or reverse when rolling the opposite direction even slightly. If I'm on a steep enough incline, it will roll, but with resistance and chatter. Here is a video of it.


So I began thinking it was a clutch disengagement issue. Replaced the master and slave cylinders. Bought as individual units and bench bled them. Didn't fix it.

I bought a Luk clutch kit. Replaced the pilot and throw out bearings, pressure plate, and clutch disk. The clip on the fork was broken, so I replaced that (it may have broken when I disassembled it). Sanded the flywheel. Put it all back together...no fix.

I though I may have bought a bad master or slave, or didn't do a good enough job bleeding it. So I bought a sealed master and slave unit from Napa. No fix.

When driving it, I noticed that when rolling in neutral at about 20mph WITHOUT pressing the clutch pedal and with the shifter centered in neutral, it chatters. While it is chattering, I can't shift into any gear. Once the chatter stops, I am able to press the clutch and shift. While it is chattering, if I pull the shifter towards a gear, without pressing the clutch still, the chatter stops. Since this has nothing to do with the clutch, I'm thinking that it isn't a clutch issue. Here is a video of it.

I'm at a loss for what to do next. I think it is the tranny (in light of the water) and probably needs to be rebuilt, but before I pull it and spend $700 on a rebuilt AX15, is there anything else I should look into based on these symptoms? Could it be a shifter problem, tranny mount issue (seems fine, but I may just not know what to look for), flywheel issue since I didn't replace it (seemed fine, no cracks)?

Sorry for the long post, and thanks in advance for the help.
 

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Discussion Starter · #4 ·
Yes, but you can still feel it through the shifter. A ticking, if that makes sense. It just isn't as audible with the clutch depressed, and you can't feel the whole jeep shake.

And if I depress the clutch while it is chattering and try to shift from neutral to second, it won't go into gear and I can feel the spinning through the shifter when I'm up against the gear. It won't grind or go into gear until the jeep has slowed down to almost a stop.
 

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When you drained the gear oil were there gold flakes in it?
How about shifting out of gear with the clutch in and engine running....is it harder than normal?
 

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Sounds like his clutch is not releasing

If it won't roll freely in a low gear with clutch all the way down the. That would be my guess

Find a flat parking lot away from everyone shut the jeep off and with transfer case in 2 hi and tranny in first and Park brake off and no foot on brake pedal now with clutch pedal all the way down still no brake and leave tranny in gear and crank the starter.
Does the jeep move forward when starter spins the engine?
 

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Sounds like his clutch is not releasing

If it won't roll freely in a low gear with clutch all the way down the. That would be my guess

Find a flat parking lot away from everyone shut the jeep off and with transfer case in 2 hi and tranny in first and Park brake off and no foot on brake pedal now with clutch pedal all the way down still no brake and leave tranny in gear and crank the starter.
Does the jeep move forward when starter spins the engine?
I agree.
 

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Discussion Starter · #8 ·
I didn't see any brass in the fluid.

Jeep doesn't move when starting with the clutch depressed.

I agree. It seemed to me like it wasn't fully disengaging. But after replacing the hydraulics, and clutch parts other than the flywheel and fork, what else could be causing it? Could the clutch cause the chatter when rolling in neutral?

There is a chance that the fork was slightly bent. I didn't really inspect it too closely but I don't think there was an issue. If it was bent, it wasn't much though.
 

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Discussion Starter · #9 ·
Wouldn't the jeep lurch forward when running too, not just when cranking it?

I also tried pushing the clutch in, putting it in gear, and reving the engine without the brake to see if it would move forward and it doesn't.
 

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With slight drag of clutch brakes will win so if park brake set or foot on brake even with drag it won't lurch forward so what does it do if you try what I posted
 

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Discussion Starter · #11 ·
It doesn't jump when starting on a flat surface with no brakes.

Is there any other explanation for the fact that it won't roll freely in gear with the clutch depressed? I wondered if it was tcase or diff related, but it rolls when in 3rd gear and higher. Maybe an driveline alignment issue of some sort?

It seems that clutch drag would explain everything other than the rolling in neutral chatter. It would also explain the grinding and inability to downshift. But all of the clutch components other than flywheel and fork are new.
 

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With clutch in (pedal down) it should roll freely and tranny gear should make no difference

What a higher tranny gear does is require less engine spinning for a given roll speed with clutch pedal up

Think of if as a lever arm
In low gears like 1st or reverse engine has big lever arm over wheels and wheels have small lever arm over engine so easy for engine to spin wheels and hard for wheels to spin engine

In high gear like 4th or 5th exactly the opposite
 

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If it isn't clutch related, there has to be something locking up/binding in some other part of the drive train. If different gears produce different amounts of resistance, my guess is that it would have to be an alignment issue between input and main shaft of the transmission.....possibly a transmission input shaft bearing that's toast?

You might want to pull the rear drive shaft, and have someone depress the clutch while you turn the t-case out put shaft by hand. If it still is binding up, start it up and use a mechanics stethoscope to see if you can pinpoint the noise.
 

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I figure the gear difference in free roll means clutch is not disconnecting tranny from engine completely and that slight drag while not enough to lurch jeep forward with starter is enough to screw up shifting

So I am still betting clutch drag issue possibly related to damage from operation under water maybe clutch plate is swelled thicker

Good news is tranny is probably ok but bad news is that either way he is gonna have to remove tranny and replace damaged clutch components

But never a good idea to drive a vehicle you like and plan to keep thru deep water unless a true emergency with no choice
 

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Yep, sounds like either way he's going to wind up pulling transmission....at least that way it might give him a definitive answer.
 

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Discussion Starter · #16 ·
I definitely didn't intend to drive it through deep water. It had just rained a bunch and I didn't realize how deep it was. It looked like a puddle.

I put a couple thousand miles on it after the water episode before problem started showing.

All clutch components have already been replaced with a new LUK clutch kit. Everything but the flywheel and clutch fork.
 

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Discussion Starter · #17 ·
Couple of more data points. Thanks for all of your help.

I tried the roll in 4H. Still won't roll freely. Not sure if that should matter.

When idling (engine running while stopped), if I try to shift into 3rd or 5th WITHOUT the clutch pedal depressed, there is no "stop" and it will freely clash the gears. Very high pitched whine. In any other gear, if I try to shift into it when idling without the clutch depressed, you hit a "stop" and it doesn't allow the gears to touch.

3rd and 5th are my grind issue gears when driving. This points to trashed synchros, correct?
 

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I'm thinking if the symptoms are exactly the same as they were before replacing all the clutch parts, and you're sure all the clutch parts were installed correctly, that leaves transmission. Since you have to pull the transmission to get to either one anyway, it seems to me the best option would be to pull it, recheck your clutch install and check the operation of the transmission out of the jeep.
 

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10-4.

How would you check transmission operation out of the Jeep?
I would think if there is a binding issue while in neutral that is enough to not allow the Jeep to roll, you should be able to feel it between input shaft of the transmission and output shaft of the t-case.
 
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