2000 XJ. 3 inch lift. 31 inch tires.

Have a loud clunking noise while accelerating/ decelerating. If I ease on or off the gas it is not as loud and if I just let off or hammer on ( most of the time anyways.)

While shifting from R - D / D-R it is extremely loud.

Any suggestions on what to check and how?

Thank You.

 

Check clearance between exhaust pipe and crossmember.
Also check motor and trans mounts

 

On top of what was said already look at your engine to tranny "connecting" bolts.( holding engine to bell housing) pretty scary.

 

Ok so the U-Joint seem's solid. Next thing to check seem's to be the Tranny Mounts. Can anyone provide a diagram or pic on where the mounts are located? Or is it obvious? I don't think I have every eyeballed them before. Any info would be greatly appreciated.

 

There is one transmission mount and two engine mounts. The transmission mount is right on top of the crossmember. The engine mounts are on the left and right side of the engine. Look for signs of sagging, cracks, or if the rubber feels spongy from oil soaking into it.

New vs Old transmission mount



Motor mounts.
The one on the left is OK but the one on the right is cracked and sagging.

 

Ok, I must have been mistaken about the u-joint. I check motor and tranny mounts and they are all good. My XJ was in 4wd full time while I was hearing the clunking before. I just manually shifting it into 2wd and when I go from R-D / D-R there is minimal noise at all. When I am back in 4wd it is loud. Would that indicate the front u-joint?

 

anbody?

 

Yes that would indicate it is more likely one of the front U joints, or the front joints are i. Worse shape. There are three in the front prop shaft and two in the axle. Probably in the prop shaft.

How have you gone about checking them?

Also, you havn't mentioned if this noise is constant or just intermittent, such as only when you shift.

 

Noise is constant. Any time I hit the gas or remove foot from pedal there is a loud noise. Also while shifting. The noise is much more noticeable while in 4wd. If I rotate the front driveshaft by hand I can hear the same noise just not as loud. Sounds like it's coming from the front diff area.

 

Okay "anytime I hit the pedal" is NOT constant. Which one is it?

Is this done with the Jeep in the ground? If the front U joint is toast you should see the drive shaft yoke move, but the pinion yoke will stay still.

BTW are you using 4WD on pavement?

 

It is anytime I hit the pedal or release the pedal. Not while under throttle. Yes I am using 4wd "Full time" on pavement. Can you help me identify the difference between driveshaft yoke and pinion yoke? I have not replaced U-joints before nor have I identified there failure without having a shop tell me and have them replace them so basic english is key please.

 

Phew not Part-Time!

Sure. First check out this diagram:



A U joint yoke simply looks like this:



On the XJ, joints are fastened in with little straps and some bolts.

The pinion is the driving gear inside the axle. That's where the yoke from the drive shaft goes.



When A U joint goes, with pretty much exactly the symptoms you've described, the needle bearings inside the caps have disintegrated.



When this happens, the cross will flop around inside the cap. You check for it by turning the driveshaft with your hand (make sure it's either in Neutral or 2WD for the front shaft)

 

Had a similar problem, clanging noise everytime off and on the gas most noticeable when driving slow. Turned out to be a bad universal joint on the front axle shaft end by the wheel. Was a real pain to remove as had over 25 years of rust holding the hub together.
Hope this helps.

 

Thanks for the help guys. Those pictures really helped. I am sure the u-joint is toast now. The only thing i'm not sure of is if I should buy a u-joint press and get after it or take it to the shop (no tool rentals within 2 hours of me ). Probably be around the same price
Thanks again guys.

 

If you've never done it it's best to get it done. They can be done without a press. Would be nice if you could get someone who KNOWS HOW TO DO IT to walk you through it.