Fighting a vibration

[Washout]

During my recent engine rebuild I used the down time to rebuild the torque tube with all new bearings, rubber donut and heavy duty support bushings. The original drive shaft bearings were not changed. Now I've got an annoying vibration that I can't quite locate. The vibration is speed dependent. Pushing in the clutch or taking the car out of gear does not effect the vibration. It is at a wide range of speeds only getting better or worse at some speeds but never fully disappearing. The vibration seems to be worse with a passenger in the car. I tried a spare driveshaft and found no improvement.

Any ideas of where I can go next trouble shooting?

[wrench459]

what all was changed during the engine overhaul down time?
I would try some hose clamps on the drive shaft first
you may have to play around with how many clamps and position
just my two cents worth sounds like driveline vibs

[wrench459]

another thought remove the driveshaft turn it 180 degrees
after making sure the u-joints are good
and properly seated in the yoke

[ungermm]

I'm going to assume that this is a new problem that wasn't apparent before working on the drive line. You should check the U-joints to make sure all 4 hubs one each joint are properly in place. If they are then, I would first jack up each wheel at a time and roll them checking for smoothness of rotation and any play when you push or pull on them. Then, with just the rear end safely jacked up or on stands, have someone run the car in gear while you check very carefully to see if you still notice the vibration. If you do then you might be able to narrow down the area of vibration. If no vibration, then you may have a front wheel balance problem. Vibrations are hard to narrow down. Generally, they appear when something is out of balance. Jerry

[Washout]

Thanks for the suggestions, I'll try these out today. It really is aggravating, this new engine is really nice but I can't enjoy it for the vibration. I'm pretty sure it is restricted to the driveline.

Of course like an old buddy of mine says "that's OK, if you can't figure out what is wrong just wait until it turns into something you do recognize."

I'd like to avoid that scenario.

[hrcollinsjr]

Engine runs smoothly, correct? So no way it's an engine problem.

Check all the obvious stuff first just to verify that you didn't do something dumb. I've found too many times that we can't see the forest for the trees. Some of these things have already been mentioned such as making sure the u joints are properly seated, wheels are tight, engine & trans mounts, etc. We tend to examine things more closely after a repair and notice things that may have been there to some extent all along.

Good luck and keep us informed of your progress.

Harold

[baronbors]

Just a reminder to check your tires- a ply separation can do it too.

[Washout]

Well, I find that the u joints are properly seated and I find no unusual slack in the wheel bearings. I did find that the housing for the torque tube was touching the floor of the car which may have been transmitting some of the noise and vibration I am feeling. While running the car on stands I did notice more tire runout (wobble) than I expected. I setup a dial indicator on the rear wheels and found .050 runout on the right rear and .030 runout on the left. I took the tires and brake drums off and checked the runout directly on the axle flanges. I had .003 runout on the right axle and .008 runout on the left axle.

I figure some of the problem may be cleaning between the axle flange, brake drum and wheel flange as well as proper torquing of the lugs. The .008 seems a little excessive to me but I was unable to find anything about it my FSM. I have a spare rear end here and the axle I checked on it showed .003 runout. Does anyone know what the max runout is on these axles?

I've already had the tires balanced and I rotated them hoping to move the vibration but it had no effect.

[wrench459]

Originally Posted by Washout I did find that the housing for the torque tube was touching the floor of the car

theres she blows captain
fix the torque tube mount and the problem might be solved

[tomking]

Arent the torque tube mounts supposed to have a washer of about 3/16 thickness between the mount bracket and the floor?

[Washout]

The torque tube housing was touching the tunnel on the right side so I loosened the bolts and forced it over to the left until I had 3/16 clearance. Took it for a drive and found the vibration had been reduced by approx 80%. The vibration is still there but greatly reduced. I'm wondering if what remains is due to the axle runout I found earlier.

I may change out the axle with .008 runout tomorrow and see what that does. Thanks for the recommendations guys.

BTW, I do have the 3/16 washers in place between the torque tube and chassis. But that was a good thought.

[Washout]

Still chasing this vibration down. I replaced the entire rear axle Friday which again reduced the vibration but did not eliminate it all together. It is still speed dependent but is better at some speeds than others. It's smooth at 55 but vibrating at 70. You also seem to feel the vibration more under hard acceleration.

The biggest thing I notice now is what seems to be a harmonic vibration when slowing down with the car in neutral. When I opened up the old rear axle I found the carrier was stiff to turn as if it had a bad race on one of the bearings. I've not pulled it down yet. Today I'll pull the torque tube and check the runout on the driveshaft in the torque tube, maybe it's twisted or badly out of round.

[jmbinjax]

I recently replaced the torque tube items, ie. donut, support bushings, and upper stop. All heavy duty from OGTS. Everything went back to together fine and I didn't even forget the thick washers between mount and body. I did notice a resonance on long hard acceleration and decel in gear. Over time it doesn't seem to be that noticeable - maybe I'm just getting use to it. I'm contributing it to possibly the heavy duty components as they don't have the same dampening ability as the normal ones do. I feel comfortable it has to do with these components as I did nothing else to it at that time and I was sure to install driveshaft in same position.

[Washout]

jmbinjax,
You may be on the mark. I too used all the heavy duty components from OGTS when I rebuilt my torque tube. I'm still going to remove and inspect the shaft for straightness just to settle my mind. I have three other torque shafts here so I'll use the one with the least runout.
Thanks

[Washout]

Did some more trouble shooting this evening. All along the driveshafts I have still had the wire keeping the two U-joint caps together. Not wanting to lose that I didn't directly inspect the U-joint journals other than my rotating them to check for stiffness, or slack, and of course they seemed fine. Well today I decided to cut the wire and get a look at the journals and there was what I hope is the vibration. Each of the journals is damaged with flat spots, without a load on them you can't feel them. But they are clearly damaged, not only on the original driveshaft but also on the replacement shaft I used in the first step of this quest. What are the odds of them both having damaged u joints? Better than I expected!

What made me recheck them was a note in one of the "help letters" that OGTS sends out with their parts. It cautioned against over tightening the U bolts for the driveshaft as it could damage the U-joint. I don't know if that is what happened or they were simply worn out but at least that lead me to a possible solution. Now to find a driveshaft shop than can replace them.

[ungermm]

[QUOTE=Washout;13096I have still had the wire keeping the two U-joint caps together.[/QUOTE]

I've wondered what that wire was for. My thought was that the wire was just welded there to keep the caps in place during the assembly process. I have two shafts off the vehicle and in each case the wire is cut. Jerry

[Washout]

Update for anyone following this. The U-joint was the problem. Not being able to find anyone capable of replacing them I just modified my driveshaft to accept a modern C clip U-joint. I machined a flat on the inside of each side of the driveshaft that allowed the new U-joint to be pressed in and aligned using the C clip.

Hope this helps someone else fighting a driveline vibration. Thanks for the help and suggestions.

[jmbinjax]

Good to know! Thanks for the update.

[wrench459]

thank goodness the bad vibs are gone