Noise from rear axle

TurboTJ

TurboTJ

TJ Addict
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Jan 5, 2019
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Walnut Creek, CA
Today we started to get a strange noise that was hard to localize but it didn’t sound good. We got the noise any time the engine was producing any torque In gear. Either coasting with the foot off the gas or with the transmission in neutral the sound went away. When in gear and producing any torque at all there was a rubbing or grinding sound that seemed to be independent of engine or vehicle speed. It was louder at higher speed though. It didn’t matter what gear I was in or what configuration (2H, 4H or 4L) was selected. I checked out a bunch of things but I couldn’t find anything until I removed the rear driveshaft and I think the noise went away. It is hard to say for sure because sometimes the noise would come and go anyhow. But when I replaced the driveshaft the noise, or perhaps I should say a noise came back. It sounded different this time but it occurred under exactly the same condition, I.e., only when the engine was producing torque. BTW, the universals in the driveshaft appeared to be fine. These was no binding, grating or anything else suspicious.

So what do you think of this theory? The rear diff might be starting to fail in some fashion or another? If the driveshaft is ok, as it appears to be, what else could cause the noise only when under torque and only when the rear driveshaft is installed?

BTW, this is a 2006 Rubicon with the NSD370 transmission. The rear driveshaft is a Tom Woods DC with about 20k miles on it. The rear diff is the standard Rubicon 4.10 Tru-Lok which means it’s is 1) a gear based LSD and 2) a pneumatic locker. Aside from the noise, everything appears normal.

Ideas anyone?
 
The common culprits tend to be either the outer axle bearings or the pinion bearing, at around 300K my Dana 35 was ready for all three and it let me know.
 
TJ4Jim said:
The common culprits tend to be either the outer axle bearings or the pinion bearing, at around 300K my Dana 35 was ready for all three and it let me know.
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My bearings have about 120k miles on them. Failure at such a low mileage would be rather disappointing.
 
hosejockey61 said:
Open the diff and take a look. Have you verified that the locker works? IIRC @jjvw had similar noise with his when the locker broke.
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I have had the pleasure of breaking the rear Rubicon locker in every way possible. These things are ticking time bombs.

When the first locker broke, only the locker was affected. It wouldn't fully lock and there was a rumbling noise when there was differential action when trying to engage. Pull the cover and there will be small chunks and flakes in the housing.

This did not affect normal driving and I lived with it for about a year before I found a factory locker on Craigslist.

With the second one when the LSD broke apart, chunks of the helical gears would clog the LSD creating loud cracks and bangs. Anytime there was differential action, the diff would briefly lock up and try to push the Jeep in a straight line during a turn before that chunk broke free. Pull the cover and there will be big chunks and debris at the bottom of the housing.

If it is the LSD, there is no fix. I drove it like that for a little over a week and a few hundred miles before I could get an ARB in there. To the best of my knowledge and experience, this won't leave you stranded in the short term. But driving will be awful until you can deal with it.
 
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Thanks for the replies. I have not tried to engage the locker because I am 700 miles from home and I am afraid it will lock and stay locked. Then I will have an even bigger problem. I have not actually used the locker in a long time (months) other than to test it. This noise started in the unlocked condition. One thing comes to mind. I flat tow the a Jeep much more than I drive it. Do you suppose the LSD doesn’t like flat towing?
 
If this is the LSD, flat towing has nothing to do with it failing.
 
TurboTJ said:
I wouldn’t think so either but I am just trying to figure out why this thing would fail for no apparent reason.
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I doubt this is locker related.

Again, assuming this is the LSD, they do not like to be driven hard. Powering hard around corners is an example. Heavily relying on them as an LSD while off road is another. These things are ticking time bombs.
 
I don’t do any rock crawling, just forest roads and old mining roads. I have had to use the lockers on just a few occasions. I was hoping that the gear type LSD would be relatively bullet proof under these conditions. It does work real good on steep slopes with loose gravel. I have sometimes been amazed at places I have gone in just 2WD.
 
Mine survived 150k miles of me not being careful with it. 100k was entirely me and I ruined the locker portion, not the LSD.

The second used factory locker allegedly had about 60k miles on it. I managed to get one year and maybe 5-8k miles out of it before the LSD broke apart. And I was careful to not rely on the LSD this time. I guess my point is that it is impossible to predict what did it or when it will happen.
 
I think I was mistaken about the drive shaft. I removed it again (the noise went away) and when examine it more closely I can detect some slight resistance to movement and some noise. It also appears to have a torn centering ball seal. So when I get home I will be rebuilding that.

Next question: Is it ok to flat tow the Jeep with the rear driveshaft removed? I seem to recall a comment about not towing the Jeep on a dolly because two wheels would not be turning. I would have the same situation because the rear shaft of the transfer case would not be driven.
 
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