Oscillating noise and vibration out of 10 bolt

**BlackPearl** · 04-05-2012, 08:11 AM

I jumped in my wife's TA this morning to take it to work, its a 97. We dont drive it much except to shows and it reminded me it still has a unsolved problem.

At about 70mph, it has a "woom, woom, woom" oscillating sound and vibration out of its rear end. It does it under steady throttle and if I throw it into neutral to coast. That points to a problem after the tranny right? It also vibrates a bit more while under hard acceleration.

The PO put lowering springs on it and dropped it an inch or so but left the stock LCA and Panhard on it. Would that slight shift in pinion angle be whats making it sound like that? Has anyone has lowered theirs and still had it drive fine with stock LCA'S and PH?

The other thing I was thinking is that the PO had WAY offset wheels on it that stuck them out nearly an inch on the rear. Is it possible the axle bearings are going bad? How do you check that?

Maybe pinion or carrier bearings?

I am at a loss, it is a daily driver that never gets beat on so I dont want to put in a 9" or 12 bolt but I dont want to just blindly throw money at the rear end to have it rebuilt.

Anyone have any ideas or ways to test to point to a more exact culprit? Any reputable shops in this area (columbia city/Fort wayne, IN) that you could recommend for an honest assessment?

Thanks

**danjo11** · 04-05-2012, 09:06 AM

Im not that techy, but my old 97 did the same thing on the highway under steady throttle. Mine was not lowered or modded in any way. When the vibration got into rhythm it groaned like what your explaining but it didnt do it during in town driving. I think its just the nature of the beast.

**BlackPearl** · 04-05-2012, 09:10 AM

Did yours also have a vibration associated with it? I can't believe GM would let that go on a new car, but then again.........

**Supershafts** · 04-05-2012, 10:00 AM

Check your angle but it may just need the shaft rebalanced, does it go away if you get to 80 / 85 mph

**BlackPearl** · 04-05-2012, 10:57 AM

Had a new driveshaft installed last year, custom built from Fort Wayne driveshaft with new U-Joints, helped a little bit but is back again. Gets worse above 70-75. Stays there to 90, have not gone much faster than that. I live a stretch of highway that the cops love to nail people on.

**Supershafts** · 04-06-2012, 04:06 AM

I'd look at the shaft before the rear, rears don't vibrate unless they are literally falling apart.

Shafts can vibrate because the shop that made it used a dynamic machine which will guesstimate speed and only turns the shaft at 200 to 500 rpms (depending which machine they have), which is something i correct a lot in my area with the other 2 shops using the hines guesstimate machine.
The other issue is that when they balanced it most shops weld the weights on, which is fine but then don't recheck the balance and weld adds weight.
You may have a joint going bad also. . .