Clunk felt when letting off accelerator

[JAWIT]

So last weekend, we took an hour and a half drive and when we arrived at our destination, I noticed the Mountaineer would would make a "clunking" sound when I'd take my foot off the accelerator. This was at low speed probably less than 25 mph. It also seems to do it when shifting from 1st to 2nd gear. To me, it feels like universal joints. I took it to my mechanic yesterday, who said no issues with the u-joints. I thought it was a transmission issue since it felt like the clunk happened when it was shifting from 1st to 2nd gear on one occasion, but transmission was serviced last year and I don't experience any shifting issues. The clunking seems to occur more often if I slow down at a quicker pace versus gradually. Could engine/transmission mounts also cause something like this if not the driveline?

I had also taken it up to the mechanic since i noticed an all over vehicle vibration when we had the mountaineer up to around 65-75 mph on the interstate. The tires are new, but the tread is a bit more aggressive than what was on there, so mechanic thinks the vibration was due to tires. This same mechanic installed the tires, balanced them and did a 4-wheel alignment a few weeks ago. He is going to rebalance again.

Unrelated (I think), they noticed the right front cv boot was damp, but not dripping. It's probably a seal. They didn't think it needed to be addressed right now. I had the front and rear differentials, as well as transfer case fluids changed last year.

Any thoughts on the clunking symptoms and vibration?

 

[Littleant]

The clunking symptoms and vibration lead me to believe C/V or U Joint. As far as the tires go I have aggressive tires on my 02 jeep that are just louder but no vibration. Also check front and rear differential if 4wd. Grab the shaft and and then it back and fourth to see how much play and for the noise.

 

[JAWIT]

The clunking symptoms and vibration lead me to believe C/V or U Joint. As far as the tires go I have aggressive tires on my 02 jeep that are just louder but no vibration. Also check front and rear differential if 4wd. Grab the shaft and and then back and fourth to see how much play and for the moise.

Thanks for the suggestions. Mechanic told me yesterday they felt no play at all with the U joints, but said that in order to really determine if the are faulty, they would need to be removed and inspected by hand. I may get a second opinion on this at a different mechanic's shop to see if they too show no play in the u-joints or CV.

As far as the vibration goes, they did a re-balance. He said one of the new tires in the back seemed out of balance spec. When they put on the tires and did the initial balance a few weeks ago, I noticed that none of the tires had the small weights attached to the rim. The old tires that came off did have the weights, so I thought that was strange, but chalked it up to the new tires not needing them, as they did a 4 wheel alignment then as well. Upon re-balance, they now have weights on each tire, which leads me to believe they weren't balanced correctly to begin with. It's been rainy here the last couple of days, so I don't want to speed down the road at 70 mph in this weather to see if there is improvement, so once it dries out, I'll get it up to speed and see if the vibration is gone or at least way less than it was.

 

[Mbrooks420]

If there were no weights on the tires they didn’t balance them.

For the price of u-joints there’s no point in removing them and checking them, just replace them. Does your front driveshaft have a cv joint? If so, I’d suspect that.

 

[JAWIT]

If there were no weights on the tires they didn’t balance them.

For the price of u-joints there’s no point in removing them and checking them, just replace them. Does your front driveshaft have a cv joint? If so, I’d suspect that.

Thanks for that info on the weights. Sounds like the shop got sloppy and forgot the weights then. I have AWD, so does that mean I have CVs?

 

[Mbrooks420]

AWD doesn’t require a CV joint, but is the better way to do it. You’ll have 4 CV axles, one at each wheel, and then 3-4 u joints on the driveshafts.

 

[Larryjb]

...I noticed that none of the tires had the small weights attached to the rim. ....

Sometimes the weights are added to the inside rather than the outside rim where they are not visible from the street. Could this have been the case? Could one of the weights have fallen off?

 

[Littleant]

JAWIT u joints do not have to be loose. If a u joint is frozen and does not move a bad vibration will occur. When you accelerate from a dead stop do you hear a clicking sound. I agree with Mbrooks. If your u joints are original i would change them. AWD would have CV joint

 

[JAWIT]

Sometimes the weights are added to the inside rather than the outside rim where they are not visible from the street. Could this have been the case? Could one of the weights have fallen off?

Well, I didn't check to see, but strange that they are all on the outside upon re-balancing.

JAWIT u joints do not have to be loose. If a u joint is frozen and does not move a bad vibration will occur. When you accelerate from a dead stop do you hear a clicking sound. I agree with Mbrooks. If your u joints are original i would change them. AWD would have CV joint

I'm not sure if the u-joints are original, but likely are. I'm going to order and have a shop install them for good measure. No, I did not notice any clicking noise when accelerating from a stop, like when I'm at a stop light, but I'll double check.

Thanks again for all input!

 

[JAWIT]

I've had some time now to road test the vehicle and the vibration is gone, so it appears the shop re-balancing and using the tire weights greatly improved the situation. Also, the clunk that was felt when downshifting/coming to a stop is gone for the most part. Replacing the universal joints (the one in the front and both in the rear position) seems to have fixed the issue. So if your u-joints are original and you have 100K+ on your vehicle, it might be a good idea to replace them! I went ahead and bought Moog brand non-greasable joints since they were available locally. They were more expensive, but should last quite a while.