84 245Ti... TABs replaced, along with U-joints and center rubber donut all in the past year.

It contiunues with a persistent vibration which seems to resonate most around 50 mph. If antyhing, it decreases when power is applied and increases when throttle is backed off and "coasts."

Plan the following steps:

- Take to tire shop to see if any wheels are out of round
- replace control arm bushings
- drop driveshaft and take to a shop for balancing

Anything I am not thinking of?

Thanks

Robert

It's most likely not any of the items you have listed.You need to do the following before any expensive repairs are tried.


1. Make sure the drive shaft is properly aligned. Both from front
to back but also front half to back half. The drive shaft must
be assembled with the U joints at 90 degrees ofset. Look in any
manual.

2. Check the rear motor mount for wear. If the back of the trans.
is dropping, it will cause the drive shaft to be out of align.
This they do not discuss in the manuals but is VERY important.


3. Finally, check the center carrier for wear.

Hello Robert,

I have the same symptoms on my '86 240 wagon which I just acquired with a torn up rear transmission mount. After replacing the mount, I started looking for a driveline mis-alignment or anything that would cause enough vibration to induce failure in the transmission mount.

I did not find the problem until I backed the car up on a set of ramps and left the weight on the rear axle. The trailing arm to axle bushings were gone, (along with severe wear to every other bushing) allowing the axle to move considerably.

I am replacing all eight (8) bushings in the rear of the car to resolve the issue.($102.00 at www.autohausaz.com)

Hope it helps,

Automatic tranny? If modest mileage (150k-200k miles), then you might have a worn tailshaft bushing.

--
Don Foster (near Cape Cod, MA)

Thanks Don;

Had ruled out the t.s. bushing because it doesnt leak... there is a little lateral play though.

Robert

Yeah, a leaking seal is a strong clue.... but I don't know about the inverse -- I don't know if no leak absolutely means a good bushing. I noted that my trannies had a bit of play with new bushings, too, but I'd say that it was barely discernable -- maybe a few thous, or so.

The other thing is the character of the vibration. With a bad tailshaft bushing (as with a bad u-joint or imbalanced d-shaft), the vibration is about 4 times higher in frequency than a wheel imbalance. It becomes a "drumming" or "humming" that causes the rear view mirror to shake at 50 mph.

--
Don Foster (near Cape Cod, MA)

Trailing arm bushings? Tires out of round? I don't think so..
--
john,, 1985, 245:Ti, 251k mi..so.california,,,1974, 145, 230k mi. ..

The upper control arms or reaction rods as I call them, can go bad. Two styles of bushings used, and the steel backed ones are tougher to replace. With those done, and the previously done lower bushings you should be good to go.

Check to make sure that the two parts of the drive shaft are in phase. If you have a 50.8mm diameter shaft there should be some index marks to align it correctly. You may have to clean some grime to find them.
--
'80 DL 2 dr

yes, I found the factory marks and aligned them when installing the driveshaft.
Thanks, Robert