Clunking and chattering noise

[ghcoe]

So I have been fighting a odd noise for some time. A chattering noise like a chain grinding against something under light drive train loads, such as slowing for a stop or going down hill with light pedal. Most annoying and would usually go away with a slight blip of throttle or braking. At first I suspected the transfer case chain or some component. I had the transfer case apart three times looking for a issue in there. Finally I changed the chain with another used chain I had and swapped the differential with another which passed the bias test better. At first the noise went away and then it slowly started to make the noise again with more and more frequency with time. I even got one of the new chains and was ready for another transfer case tear down. I was doing another drive train inspect for obvious issues and came to find a bad spindle bearing. At first it was not obvious because I had the transmission in park. Once I set the brake and shifted the transfer case into neutral it became apparent that there was a lot of play where the axle stub goes into the back of the spindle. I did not even know that there was a bearing there.

After replacing the bearing the first thing I noticed was that the clunking I had when I shifted into gear was gone. I thought the clunking was due to a loose chain or some wear in one of the splined shafts, even though I could never find any wear in the transfer case, I had already checked the U-joints and rebuilt the CV-joint.

Two day of driving and no chain rattle noise so I am really hoping that this has taken care of this annoying condition for good. A bonus is that it does not clunk shifting gears now.

I think that the noise went away for awhile becuse the clutch bias on my old differential was low to the front axle. Once I replaced it with a differential that passed the clutch bias it supplied a stronger load on the front axle and kept the spindle bearing from rattling until it wore down to a point where it started to rattle again.

Now that I think about it, I never had the noise until I had a bad spline in a cone clutch. I tore down the TC to replace the cone clutch and right after that is when the noise showed up. I thought I had done something wrong with reassymbling the TC and soon after I parked the Jeep. Fast forward 9 years, once I got the Jeep up and running again I heard the noise so I figured it was still in the TC. Two tear downs later I find that the front clutch bias was out of spec and replaced the differential with one that passed spec and noise went away, for awhile. Now I am thinking that the clutch bias was good to the front axle with the old cone clutch years ago. The installed cone clutch must of been out of spec and lightend the load on the spindle bearing which then allowed it to rattle around in the housing. Me having just been into the TC thought I had done something wrong. I never checked the clutch bias back then, never even knew that could be a issue.

Figured I would post since this may come up again.

[CosmicRhino]

Glad you figured it out George, now come do mine :] Not getting much rattling, but I've got the reverse-shift clunk. Ordered a new QT chain and seals set from BJ's, hoping that will take care of mine.

[ghcoe]

Just realized I put this in the off-road section. If someone wants to change it to stock jeep tech that would be cool.

[Tatsadasayago]

Glad you figured it out George, now come do mine :] Not getting much rattling, but I've got the reverse-shift clunk. Ordered a new QT chain and seals set from BJ's, hoping that will take care of mine.

Does your case have a part-time kit in it?
If so, you may be disappointed when the clunk is still there after you replace the chain.
I recently did the same thing and mine still clunks but the chain is tight.

I suspect the replacement shift collar design is part of the problem due to the spacing of it's teeth which allows the output shaft to turn against the driven hub quite a ways before taking up the slack.
Interestingly enough, I discovered that if I am going to back up, it helps to be rolling forward, shift into neutral, then reverse when the vehicle is barely rolling forward. This makes for a very soft and clunk-free backup. Definitely not a fix, but a good workaround.

[ghcoe]

No part time in my case. The clunk is still there, but definitely not as frequent or loud. I am suspecting the other spindle bearing is probably going out as well. I think the best way to check for the clunk at the spindle bearing is to watch the spindle bearing area and have someone shift the transmission from drive to reverse. Make sure the wheels are chocked, don't want to become a casualty. I think if the bearing is bad you will see the U-joint yolk jump as the load is transmitted through the drive train. I am thinking that is where the cluck comes from and transmits to the TC. That is the main reason I always suspected the TC because it sounded like it was coming from the TC area!

I was trying to check the U-joint behind the spindle to see if it had any slop when I noticed that I could move the whole yolk about 1/4 of a inch. I thought that does not seem right so I checked the other side and it barely moved. I used a screwdriver with the TC in neutral. I was able to use the lower ball joint nut for leverage to move the U-joint yolk with a screwdriver. With more investigating I found that there was a bearing there so I figured it was bad. A bearing kit which includes the bearing , disc and two seals was only $13.00 at six states. Installation included renting a bearing puller kit and a spindle removal tool which I was able to rent at Auto Zone.

Still no rattling. Tomorrow should be the big test. Jeep trip up to Silver City so crossing the fingers.

[CosmicRhino]

Glad you figured it out George, now come do mine :] Not getting much rattling, but I've got the reverse-shift clunk. Ordered a new QT chain and seals set from BJ's, hoping that will take care of mine.

Does your case have a part-time kit in it?
If so, you may be disappointed when the clunk is still there after you replace the chain.
I recently did the same thing and mine still clunks but the chain is tight.

I suspect the replacement shift collar design is part of the problem due to the spacing of it's teeth which allows the output shaft to turn against the driven hub quite a ways before taking up the slack.
Interestingly enough, I discovered that if I am going to back up, it helps to be rolling forward, shift into neutral, then reverse when the vehicle is barely rolling forward. This makes for a very soft and clunk-free backup. Definitely not a fix, but a good workaround.

Funny, I've noticed the same thing works for me to shift to reverse 'clunklessly' and felt like it was backwards logic, but I guess it works.

I'm new to the QT and FSJs in general, maybe you can help me clarify what I have.



I've got a QT with a reduction unit, right? Is there any way to tell if someone before me has installed a part time kit without opening it up? The hubs are in free and have been since I picked it up. Presumably that means there is a part time kit? Maybe I've read incorrectly, but if you have full time you have to keep the hubs locked at all times or you'll burn up your t case?

[Tatsadasayago]

You are correct. Hubs are a good sign of a part time kit being installed.
Your TC is the usual Borg Warner 1339 with the reduction unit.
Having hubs on the front end isn't a 100% guarantee that it has a part time kit since I've run across many that did yet were still original inside.
You can check the glove box dial for an updated E-Drive decal which most installers took the time to place there.
Lastly, with the hubs in FREE, you can spin the front driveshaft easily if there is a PT kit installed. If it turns with quite a bit of effort, the TC is probably still full time.

[Tatsadasayago]

BTW: I suspect the reason the 'Clunk-less' trick works is that while rolling forward in neutral, the transmission's overrunning clutch is starting to engage and somewhat braking the output shaft. Going into reverse causes the clutches and servos to apply softly. My theory is that between the overrunning clutch and clutches/servos applying there is a braking effect on the output shaft, TC hub, chain and output shaft.
I know that if I come to a complete stop in neutral, or stop in drive, then go to reverse, I get a hellacious clunk.

[fulsizjeep]

Moved to Stock FSJ Tech.

Assuming the QT vacuum shifter is working OK... I start with drive shaft ujoints then front axle ujoints when the clunk chatter starts. The front drive shaft is not always revealing installed, so I drop it for inspection. While drive shaft is out, good time for a bias test on QT. Then I pull the low range and check the ten spline shaft and sun gear. Inspect fluid for metal. A couple times I have found the low range unit loose and fixed the chatter by tightening it back down. So many things can play into the noises a QT FSJ can make.

Determining whether a QT has a part time kit or not is very difficult without opening it up. If you can see under the shifter inspection cover, there is a visual difference at the shift collar (stock) or slider (part time). I thought I had one out of a 75 Waggy once but when I opened it up, it was all original except someone had taken a cone washer out of each side of diff making it an open diff floating in ATF.

In this picture you see a stock diff and a PT 16% OD diff.