just bought an xj and it has a vibration that starts at about 30mph and it vibrates when im on the gas. if i let off the gas and let the truck coast it goes away. any suggestions on what it can be or any tests i can do to figure out what it may be

 

Welcome to the forum! Hope some of the smarter one's here can help you with all your upcoming questions in the future.


Really need more information to be helpful. Is the engine that does this (misfiring), the drive line (U-Joints?), axle shafts? Can you be a little more helpful in your description there are quite a few things that can do this?

 

Wobble in torq converter? Does it vibrate even at low RPM's?

 

Does it have a lift and if so, what size?

I bet it is a bad U joint on your driveshaft though unless you have a larger lift on the cherokee.

 

Dollars to doughnuts someone removed the rear drive shaft, likely to replace a U-Joint, and reinstalled it 180 off. The rear drive shaft is balanced with the yoke. If you install it 180 degrees off, it will vibrate exactly as you describe.

It's kind of a pain, but if you disconnect the rear U-Joints, rotate the drive shaft 180 and reinstall it, you'll immediately know if that the problem. If it was, the vibration will go away and you're done. If that's not the problem, the vibration will be worse and you'll have to rotate the drive shaft again.

While you're under there, inspect the U-Joints. If they're shot, that would also create the symptoms you describe.

 

I wonder if it has any lift?

I added heavy duty rear leaf springs yesterday to my XJ. With the new springs it is about 6" higher than it was in the back, and there is now a little vibration at around 35 mph, but only while accelerating. It had no issue 2 days ago, which was before the spring replacement.

As the springs settle and the rear lowers a little, I'm guessing this will go away for me.

If yours had a lift, it could be throwing the drive line stuff off - as I understand it, it causes some binding if the lift changes the angle too much.

 

We really need to know more about your vehicle. If stock then it could be a u-joint. If it's lifted then it could be driveline angle, worn driveshaft u-joints/ centering ball, or an unbalanced droveshaft. In either case it could also be shot bearings in the rear end.

 

I would say driveline. If it vibrates as it's loaded up and goes away while coasting I would say U joints on one of the driveshafts

If the vibe is felt in the pedals it's up front, in the seat rear. I'd start there, they probably need replaced anyway. If they are new you should probably have the differential looked at

 

Please take to your local automotive repair shop for a professional diagnosis. You DO NOT have to have them do the repair. Once you know exactly what is causing the vibration. You can get help on how to do the repair yourself.

 

thanks for all the posts. it is a 92 cherokee 4.0 4wd with a 3 inch lift. i tried to shake the driveshaft around to feel for any play in the u joints but it seems to be solid. i feel it mostly in the peddle

 

The U joints won't feel sloppy if bad. If anything they will be binding and tighter

Could be front axle U joints or it could be the front driveshaft

In all honesty if it's a 92 I'd replace them all no matter what the real problem is just to rule out future vibes. If the lift is new and so is the vibe, I would look at the rear shaft and consider an SYE or dropping the cross member for the trans an inch. I chased vibes forever on my 3" 00 and in the end the SYE finally fixed it.

These things have 7 U joints in them and they all will go bad eventually.

Rent a press, buy a pile of U joints and camp out under that thing for a weekend. Replace the hubs while it's apart if you can afford it. Timkin hums only. they are about $120 each but they won't fail in a year.

If you do not have the coin and MUST do it a part at a time you may want to take the advice above and have a shop diagnose the issue and then DIY

 

Hi: I have the same problem. My xj is a 2000 w166k. I've had this problem for over a year,local garage says frt&rear u joints feel ok,r/f axle u joint was changed because of dry bearings,but had nothing to do w/problem . I've worked on my own cars for at least 60+ years, can't do much anymore like I used to. Seems to me if it was a u joint it would have gotten much worse by now,just sayin". Hope someone can be a little more definite w/repair. Don't want to get nickled and dimed to death to fix this teen agers problem