Vibes after replace trans.sup., cent.bearing & u-joints

[dantye]

I have replaced the Transmission support (was dropped down about 1/2 "), u-joints and center bearing in the drive train. Also rear trans seal. Now there is a very slight but noticeable vibration you can notice only between 30 and 40 mph on a smooth road. Not particularly noisy, but too regular a vibration to be the e-brake cable or such. Tried engine braking in all gears and did not produce any particular effect. Drives fine above 40-70 mph with no sign of the vibration. Having front-end alignment done soon, and wondering if I should have the drive shaft balanced too, but most drive shaft balance problems I have read about here seem to be at higher speeds.

Rear end has fresh oil and never had any leaks, but I have read that worn out trailing arm bushings could lead to diff issues - possibly accentuated by tightening up the drive train? Any ideas on how to check for that?

Thanks!

[redcars]

Did you mark and keep all your drive line parts in the same relationship to each other as they had before you worked on it. If not then the drive line is out of balance as it was balanced as a unit when new.

[dantye]

Did you mark and keep all your drive line parts in the same relationship to each other as they had before you worked on it. If not then the drive line is out of balance as it was balanced as a unit when new.

That seems to be the problem. The first folks that worked on it were clueless and apparently put the two sections together 180 degrees off. Having it flipped Monday and we will see.

Thanks

[narfire]

jack the rear of the car up. Block it securely. Start the car, put it in 3rd gear and with a long stick push the gas pedal while looking underneath the car at the drive line. perhaps a little hokey way of doing things but it worked, but I found my U-joints were out of whack and adjusted the cups just a tad and all was smooth after.
Chris

[dantye]

jack the rear of the car up. Block it securely. Start the car, put it in 3rd gear and with a long stick push the gas pedal while looking underneath the car at the drive line. perhaps a little hokey way of doing things but it worked, but I found my U-joints were out of whack and adjusted the cups just a tad and all was smooth after.
Chris

Thanks for the tip, but since this has had the same symptoms with both the old and the replacement u-joints installed, that is not likely here. It seems that the first BOZOs who worked on it just put the two sections together 180 degrees off. The vibration occurs most noticeably at about 30-40 mph and is much more evident on a smooth road. It also is there whether you are under power or coasting, and particularly when coasting, it is apparent that the center bearing on the drive shaft is the primary transmitter of the vibration into the car.
Hopefully, I will know for sure after it is rotated 180 in a couple of days.