Crunchy Rear End Sounds

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Brendon Holt

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So ever since shortly after I bought the Liberty I began to notice that there is a weird crunchy sound from somewhere in the rear. It seems to happen mostly when you shift weight or direction. Think of going around a roundabout and then turning out of it, that shift in weight and direction seems to elicit the crunchy response from the rear. Rarely makes noise over bumps in a turn or in a straight line. It doesn't really sound like gears binding. It's more of a scrape/crunch kind of sound, to the extent that one of the things I checked for was tires rubbing in the rear under hard turns but no signs of rubbing.

My theories (In no particular order):

1) Something to do with the rear sway bar being over tightened. I read some people having issues with this.
2) Chatter from a Trac-Lok rear end that needs friction modifier. Pulled the build sheet and spun the wheels in the air so I know I have a Trac-Lok rear end.
3) Worn out tri-link. Still unclear as to how exactly this one would make this sound but it's connected to so many components that move during corners it seems like it could be a suspect.
4) Worn out shock(s). Because, well, they can make those sounds when they go. But it doesn't make the same sound over, say, a speed bump and on bumpy roads. It's actually fairly smooth and quiet in a straight line. So Idk.

What do y'all think?
 
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turblediesel

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Find an empty parking lot and do about a dozen slow, tight figure-8s. This gives the trac-loc a little workout that makes everything move. I think it's in the FSM.

Or parking brake noise?
 

tommudd

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Trash lock needs fluid changed, new modifier installed then driven in tight circles both ways
using dino fluid
 

Brendon Holt

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Trash lock needs fluid changed, new modifier installed then driven in tight circles both ways
using dino fluid

There is nice new fluid in the diffs and TC (changed before I bought it and have visually verified that it's in there) so do you think it's fine to just add the friction modifier and do the tight circles routine? I can't verify that the fluid that's in there is dino fluid, tho. Just that it's new.
 
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LibertyTC

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Change the gear oil out, with the Mopar 4 oz bottle of limited slip additive.
Do not use synthetic gear oil- Dino only. I use Lucas 80W-90 or 85W-140 if trailer towing.
Service on the rear diff should be frequent. I change mine every 30K.
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Brendon Holt

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Change the gear oil out, with the Mopar 4 oz bottle of limited slip additive.
Do not use synthetic gear oil- Dino only. I use Lucas 80W-90 or 85W-140 if trailer towing.
Service on the rear diff should be frequent. I change mine every 30K.

Fiiiiiine. I shoulda known y'all wouldn't let me off easy on this one ;)
 

Royy

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Check the exhaust hangers as well. They tend to rust pretty badly over time. A couple of years ago one of mine broke off, and as a result the tailpipe would intermittently rub against the inside of the wheel well, creating all kinds of weird noises. Took me forever to track that one down. If one of them is broken, that allows the muffler and tailpipe to 'swing' more, which could explain why you hear it after a shift in weight/direction.
 

Brendon Holt

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Check the exhaust hangers as well. They tend to rust pretty badly over time. A couple of years ago one of mine broke off, and as a result the tailpipe would intermittently rub against the inside of the wheel well, creating all kinds of weird noises. Took me forever to track that one down. If one of them is broken, that allows the muffler and tailpipe to 'swing' more, which could explain why you hear it after a shift in weight/direction.

All exhaust hangers are good. That was one of the first things I checked as well.

Had the same issue with my 2007 KJ. Rear sway ball joint worn out. (#19). Replaced rear sway bar and problem solved.

That's the tri-link right? I notice a little bit of movement in the ball joint above the diff if you rock the wheels back and forth in park but not crazy and I plan on replacing it but it doesn't make noise. Not to say it couldn't under side to side forces though.
 

Brendon Holt

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Oh interesting bit of additional info: I've noticed that on hot days it doesn't happen as much or at all. Drove home this afternoon while it was 81 and didn't hear the noise at all. Idk what exactly this means but it seems like a useful piece of information.
 

tommudd

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Had the same issue with my 2007 KJ. Rear sway ball joint worn out. (#19). Replaced rear sway bar and problem solved.
Rear sway bar does nothing and does not have a ball joint ( all of mine have had their sway bars removed and the balls as well for years ( the 04 hasn't had a sway bar in the rear for 15 years and over 230,000 miles LOL)
only the rear tri link has a ball joint
 

Brendon Holt

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Rear sway bar does nothing and does not have a ball joint ( all of mine have had their sway bars removed and the balls as well for years ( the 04 hasn't had a sway bar in the rear for 15 years and over 230,000 miles LOL)
only the rear tri link has a ball joint

This makes me feel better about just taking the sway bar out. The balls are good to take off too, eh? Are they supposed to be some kind of balancing mechanism for the driveline?
 

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