The Stovebolt Site Forums The Shop Area Driveline Driveline Hum/Vibration

Howdy all. I've got a conundrum. '54, 235, 3 speed, torque tube. Drive it all the time, ~30 mile commute mostly highways. A while ago, in town, pulling away from a stop sign, going uphill, KachunK. could still move, with KachunKs, got it to the side and towed it home. Thought I did something to the rearend. Pulled cover, looked it all over, looked good, ran through gears while in air, no problem. When holding brake while letting out clutch could feel start of KachunK. Not audible though.
Next step, removed torque tube from back of transmission. Victory is mine! One broke bolt in u-joint. Found head, able to unscrew broken shaft. Ordered new bolts and keepers, and replaced. Topped off all fluids.

Here's the problem. Now I have a vibration - fast frequency like a 'Hummm' that starts around 30 mph, and is most noticeable from 45-55 mph. pronounced enough that it vibrates the rearview mirror a lot. It definitely wasn't there before. Seems to be most pronounced when cruzing at constant speed. Acceleration and removing foot from gas reduces the volume, but it is still there. Put in clutch while cruzing, still there.

So, almighty Stovebolt brain trust, what do I do next?
Any help would be appreciated.

Not a torque tube expert by any stretch of the imagination but you might try unbolting the joint and rotating 180 degrees and bolting it back up. Might just be balanced better that way. Just an idea.

I agree with above. Redo I joint 180 degrees and see if it goes away

-or the kachunKed bolt is a symptom of another problem, such as a worn bushing in the torque tube. I just can't imagine that bolt giving up like that unless it was under stress from something else wrong in there.

Thanks for the quick replies guys! Looks like i will try to tear it apart next weekend, have company this week. Still drove it today. The vibration isn't consistent, more intermittent - quiet last night on the way home, just one short vibration episode on the way in today. Does this change any ideas?

52Carl - Yes, that has been wearing on my mind (*haha pun not intended). Forgive me for asking before I consult my shop manual tonight, How do I check the bushings in the torque tube?
Before the KachunK episode, it occurred to me that I was starting to get extra vibrations in the gear shift - the rattle would become annoying on longer trips. Bushing going bad, or loose keeper that finally let the bolt loosen and break?

torque tube okie bushing

This thread talks about replacement, and there was just one mention of checking bushings - Tim stated that the shaft will wiggle but was unsure of proper tolerances.
Any Ideas for proper wiggle room?

Thanks again.

The vibration could also be from a worn transmission output shaft bushing.

Forgot that I wanted to update this for people looking for answers....
removing the ujoint, and rotated the driveshaft so it was 180 deg. from the way I had it and the buzz is gone.

thanks everyone.

Thanks for the update. I haven't been right in so long I forgot what it feels like. Glad it's fixed.