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Knocking vibration - Do I have a bad U-joint?

861 Views 7 Replies 6 Participants Last post by  rubitx
This morning, the Rubi suddenly developed a knocking vibration. Thought it was a flat tire. It is something rotating causing the vibration. When I applied the brakes, tho' to slow down and pull over, the knocking vibe stopped went away. The knocking started and sounded just like a rock in the tire tread. But then increased. Tires were fine. Suspension pieces all seemed in place and tight. Got back in and drove ahead slowly and got the knocking again, increased as I went faster. But when I turn very sharply to the right, no knocking. Very sharply to the left, no knocking. Just driving straight ahead.

Feels like its coming from the rear end, but can't be sure. I have a 4" lift with the transfer case lowered to reduce driveshaft angles. Has run butter smooth without any vibes at all. Until now. Got about 54K miles. Went into and out of 4WD ok, didn't seem to affect anything with the knocking.

Bad U-joint here?? Something is amiss with a rotating part. ANY ADVICE GREATLY APPRECIATED
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Turning the sound goes away? That doesn't sound like a Drive shaft U joint to me... still might be possible that it is a front axle u joint perhaps. One suggestion if you can do it... put the whole jeep up on jack stands and put it in gear and walk around to see if you can hear where the sound is comming from.

I had this issue once, but it would go away when turning in one direction, but get louder turning the other direction and the noise was comming from the rear. Turned out it was a threaded lug bolt that had come loose on one of the rear axle shafts (alloy). So it was sticking out a hair too far and was clicking against an internal E-Brake part making the sound.
The other likely possibility would be an internal problem in a differential. That would be much more expensive than a driveshaft U-joint, I hope it is not the problem.

If that turns out to be the case - were you wanting to re-gear the axles? Now would be the time to take the plunge and spend the money if so.
When chasing vibrations, I learned from a wise man that MOST of the time, if you feel it through the steering wheel or your feet, it's the front end. If you feel it with your butt, it's coming from the rear.
Re: Knocking vibration - Problem Resolved in Unusual Way

Well, guys. I figured out the knocking thing. I deduced the problem as I watched my right front wheel go rolling off to the right of the road into the ditch and felt my brake disc rotor scrapping the pavement. I was on the way to the dealer with my buddy right behind me. Only going about 15 mph as the knocking got worse. Bada bing! I had checked the lug nuts on the wheels earlier this morning, but didn't actually get right down at the hub to see them on each wheel. My Cepek DC2's have a large black center cap that pretty much hides the lug nuts. I have locking nuts on each wheel and I saw that on all four, but... my bad. Very bad.

Turns out someone removed 4 of the 5 lug nuts on the wheel last night when I was at a friend's house for dinner. Secluded area of condos and townhomes, no lights and really dark. I didn't feel anything untoward driving home, and nothing until this morning when that knocking sound happened. Never felt anything thru the steering wheel at all. Evidently they were trying to steal the wheels, and when they figured out the locking nut was there, they stopped, or maybe heard me coming out to the Jeep.

Whatever the case, every bolt stud had sheared off, but the one with the locking lug nut was the last to go, and it had been holding the wheel on ok until this morning. Filing police report, etc, but nothing will come of that. I can't believe someone would do this. I consider it life threatening. Thankfully, no one was injured, the tire flew off to the right and not into traffic. The Rubi will need some attention, but I'm alive. If I do find the culprit(s), a visit from Uncle Guido in the wee hours will make everything alright..
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Wow!!!!!!!!!!!! :eek:

Glad your ok man and any/everyone else around! That could have been a very horrible situation! Your lucky, I think if you had been going faster this would have been a catastrophic ordeal!
I hate thieves, :dhorse:
Better yet...just let a few of your ROF buddies know and we'll take care of it. :grab:
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