YJ noise over bumps in the back
1st let me say a big HELLO to all of you. I'm a new member here. I was convinced to come here by NHCJ7 . (THANX!)
So, here's the prb...
Every bump I cross on the street, I hear this "thump" noise. Sounds like something metal & heavy gets to rub against something metal & heavy. Immagine having a rear axle that is not tightened enough with U-bolts to the leafs, so when you hit the bump, the axle jumps up, hits something, then comes down again hitting again. It is not that, it just kinda describes the sound. Plus, when it happens, I feel a light vibration coming from somewhere under the rear bench. Kinda like from the right-side back.
Now, I was suggested (by NHCJ7 - thx again) that it could be the rear driveshaft U-joint going bad. I checked the driveshaft, and it seems OK - not a minimal movement is possible, except rotating it (the way it does rotate itself when driving). Also, wheels aren't hitting anything in the wheelwell, because the movement needed to produce the "thump" sound is small - like passing down the dislevel of an inch. Front wheels-nothing. Back wheels - the sound.
It's my 1st Jeep, so I can't describe the problem much better than this. Sorry.
I had a "normal" (read: ugly, not worth mentioning) car before, and it used to make somewhat similar sound when it had it's shocks completely empty: driving a bit faster, it'd hit the bump, making the wheels loose the ground (cause of the speed) and since they were going down, they'd extend to the maximum & over, making similar sound. Kinda like lifting a car, holding the wheel compressed up with the hand and then letting it go suddenly - it'd extend and you'd probabyl hear the "thump" noise with a little vibration caused by the "pull" factor of extending shock.
If it helps, I have a stock '93 YJ (sob!), there are no driveline vibrations of any kind, the shocks are "almost perfect" (mechanic's words - checked them 15 days ago).