Another driveline vibration thread

[Laneinator]

Hey guys. So I've searched around here and other forums and most of the driveline vibrations I've read about were at, or close to, highway speeds. Not mine! I'll get a slight vibration when starting from a stop, and more so when going up a hill (under more load). Freeway speeds are smooth.

Its a '99 4.0 bone stock, AW4 with a NP231 transfer case.

A couple days ago my buddies car broke down, down the street. I drug it home through a residential area going ~3-5 MPH and the driveline was vibrating like crazy because of the heavy load.

My logic is its not bad U-joints as it doesn't happen at high speed. It sounds more like a driveshaft at a bad angle or something like that.

The rear springs are a little saggy but nothing extreme.
I got under it and was pushing/pulling the driveshaft and it didnt move much. The movement it did have came from the TC moving up and down (maybe 1/4in). Basically the rubber mount under it was stretching and compressing.

Anyone have any other ideas?

Thanks guys,
Adam

 

[Miller88]

This is pretty much the only thing I have left on my search for driveline vibrations. I have replaced pretty much everything and still having them. What I found was I can move the engine/trans all around - it very well could be causing your issue.

Remember, your engine /trans/tcase would rather rotate around than move 3200 pounds of XJ and 3000 pounds of car. It probably worked itself to such an angle that the driveline wasn't happy.

 

[joejeep92]

Also, you can find a u joint vibration by changing the driveline angle as you did by adding weight. However, the vibration at take-off makes me think more mounting rather than u-joint.

 

[Miller88]

I missed the 3-5MPH part. You're not spinning the driveline fast enough at those low speeds to cause a vibration.

My guess is the engine was rotating around and the exhaust was hitting something it should have and reverberating back into the cabin.

 

[Black Squirrel]

Axle wrap

 

[Laneinator]

My guess is the engine was rotating around and the exhaust was hitting something it should have and reverberating back into the cabin.

It's for sure a driveline vibration judging by the severity and feel of it. It reminds me of the driveshaft center support bearing going out in my bmw.

Axle wrap

You think its possible on a stock XJ? I didn't feel any wheel hop in the rear end, but this is my first leaf'd vehicle so I don't have any personal experience with that problem.

 

[Laneinator]

The rear pinion seal is leaking too, if that bearing is bad could that cause vibration?

 

[8Mud]

The rear pinion seal is leaking too, if that bearing is bad could that cause vibration?

That was going to be my guess. The bearings could be bad, if it is a 8.25 rear end the collapsible sleeve may have collapsed and your bearing preload is gone. The pinion and ring don't match up well and can cause a vibration or almost stick slip type of feeling. Happened to me I seriously overloaded a 8.25 rear and had the sleeve collapse on me. Slap the side of the yoke with the palm of your hand hard (gloves) sideways and you can often feel if it is loose or not.

My also be your U joints, when they go bad the drive shaft can wobble enough to prematurely wear the pinion seal out. Happened on my front, the slip splines got way loose (side play) and the front drive shaft wobble messed up my pinion seal. One of the first indications of bad U-joint is it spits a little grease past the rubber ring seal on the U-joint bearing cap. In later stages of failure, after all the grease is long gone, it may have a ring of rust on the rubber bearing cap seal.

 

[Laneinator]

That was going to be my guess. The bearings could be bad, if it is a 8.25 rear end the collapsible sleeve may have collapsed and your bearing preload is gone. The pinion and ring don't match up well and can cause a vibration or almost stick slip type of feeling. Happened to me I seriously overloaded a 8.25 rear and had the sleeve collapse on me. Slap the side of the yoke with the palm of your hand hard (gloves) sideways and you can often feel if it is loose or not.

My also be your U joints, when they go bad the drive shaft can wobble enough to prematurely wear the pinion seal out. Happened on my front, the slip splines got way loose (side play) and the front drive shaft wobble messed up my pinion seal. One of the first indications of bad U-joint is it spits a little grease past the rubber ring seal on the U-joint bearing cap. In later stages of failure, after all the grease is long gone, it may have a ring of rust on the rubber bearing cap seal.

Awesome, I'll give those things a look. Thanks.