Clunking on acceleration from rear but not coasting

[mbed]

Suddenly get a clunking sound, almost like a semi flat tire while driving. Only occurs while accelerating but if I let off gas and coast, the sound goes away. Initially thought it may be U joints on main drive shaft but supposedly they were replaced when trans was rebuilt about 3mos ago...they look somewhat new as well. Is it possible to post a video to this forum? Thanks in advance!

2002 Ford Explorer Eddie Bauer with ~208k mi

Just noticed a tiny bit of play in back rear wheel...can a failing hub bearing make the sound in the video? Thanks again!

 

[mbed]

Here is the rear U joint...look newish (supposedly replaced (3mos/3k mi ago?)...

 

[Stephenms]

That certainly does sound like a Universal joint or differential chatter. U-joints can look completely undamaged and still be bad. If they were cheap ujoints they could have premature failure or just been bad out of the box. My 87 Corvette had that noise while I was driving one day, I thought it was transmission chatter but when I got the rear end off the ground I applied hand torque to the rear tires(moving the tires back and forth very abruptly and listening) come to find out I hear a pop from the right rear half shaft drive shaft. When I got it apart it looked totally fine until I went to remove the universal joint from the shaft. Two of the caps had no bearings left and were slapping the inside of the cap, basically there was a quarter inch slack and as you accelerate and apply torque that quarter inch is smacked by the rest of the universal joint. That's why you only hear it under acceleration. Or you're low on differential fluid and your gears are grinding. But to me it sounds like universal joint. Differential wouldn't be that harsh of a noise unless something is loose back there.

 

[Hugh Janus]

Suddenly get a clunking sound, almost like a semi flat tire while driving. Only occurs while accelerating but if I let off gas and coast, the sound goes away. Initially thought it may be U joints on main drive shaft but supposedly they were replaced when trans was rebuilt about 3mos ago...they look somewhat new as well. Is it possible to post a video to this forum? Thanks in advance!

2002 Ford Explorer Eddie Bauer with ~208k mi

u-joint.

 

[mbed]

That certainly does sound like a Universal joint or differential chatter. U-joints can look completely undamaged and still be bad. If they were cheap ujoints they could have premature failure or just been bad out of the box. My 87 Corvette had that noise while I was driving one day, I thought it was transmission chatter but when I got the rear end off the ground I applied hand torque to the rear tires(moving the tires back and forth very abruptly and listening) come to find out I hear a pop from the right rear half shaft drive shaft. When I got it apart it looked totally fine until I went to remove the universal joint from the shaft. Two of the caps had no bearings left and were slapping the inside of the cap, basically there was a quarter inch slack and as you accelerate and apply torque that quarter inch is smacked by the rest of the universal joint. That's why you only hear it under acceleration. Or you're low on differential fluid and your gears are grinding. But to me it sounds like universal joint. Differential wouldn't be that harsh of a noise unless something is loose back there.

any chance it could be the rear wheel bearing / hub assembly? Just noticed it had a tiny (~1/16-1/8"?) side to side play...thanks again for your opinion!

 

[Stephenms]

Same thing with the differential. It would be more of a grinding or rubbing, not a clunk. Anything is possible but bearings are unlikely.

 

[mbed]

Will do the u-joints then...going with moog. Anyone have a preference between greaseless, end zerk or cross zerk, other than price? Everyone says all are great but can only pick one type so...thanks again!

 

[Stephenms]

Good choice with the MOOG. When you go to buy both joints, open both boxes and make sure they're the same cap size. I bought 4 and three/four were different sizes. It happens to some of our customers too. Fitting location is up to you. I prefer them with the grease fittings so I can maintain the joints and push out old greese when it's tune-up time. But that's just preference

 

[mbed]

Update: Driveshaft is out and the u-joints are Spicer. Only have heard great things about them and wonder how to test them. They look rather new and may have been replaced by trans shop (they don't know) about 3mos ago.

Figured out how to post pix...in next post though...they don't look bad and don't seem to have any play!

 

[mbed]

the whitish spatter is my spray paint for alignment marking...