Drive train vibration. Scratching my head.

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JoePole1 said:
I believe it's Motive gear set. No gear noise. It's the vibration that is causing the noise and only at high speed/RPM. Very faint at low speed (35).
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Ahhhhhhhhh! The old chicken or the egg thing, which came first.
You stated that this popped up after you changed the ring and pinion set.
What you have described sounds like gear noise, Cruz'n speed is the worst.
Your vibration could be a bearing going bad causing the gear to go out of proper engagement. Check the grease for metal.
 
512Stroker said:
Ahhhhhhhhh! The old chicken or the egg thing, which came first.
You stated that this popped up after you changed the ring and pinion set.
What you have described sounds like gear noise, Cruz'n speed is the worst.
Your vibration could be a bearing going bad causing the gear to go out of proper engagement. Check the grease for metal.
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Gear oil was clean when we re-checked for contact pattern and gear wear. That was after about 600 miles. The timing could be coincidental. Vibration wasn't immediate but soon after.
 
Follow up. I did 3 things. I removed the 2 hose clamps I was using on the driveshaft to determine out of balance. Remember the vibration was there prior to placement. Secondly I swapped out my trans mount with a used spare I had per RRR however I do recall doing this months ago. Lastly I noticed that the driveshaft had a 4 inch clean section djrectly above the H pipe band clamp with bolts facing up. Spun it around. Anyway the vibration only comes in around 75mph now and is mild. I will undo one thing at a time to determine which was adding to it. Doubtful it was the clamp because no damage on bolts or shaft. Maybe a nick but would have had scraping noise.
 
More follow-up. Looks like the vibration was from a combination of bad u-joints and transmission mount. I still get some vibration above 80 (no comments). I was speaking to a mechanic friend of mine and I remembered that years ago I had removed a funky looking bracket and weight (weight savings) from the back of my trans. He said that was for vibration dampening. I found the bracket but tossed the rubber isolation weight. It was about the size of a large soup can. Anyone have an idea on fabricating one or other solution for dampening?
 
JoePole1 said:
More follow-up. Looks like the vibration was from a combination of bad u-joints and transmission mount. I still get some vibration above 80 (no comments). I was speaking to a mechanic friend of mine and I remembered that years ago I had removed a funky looking bracket and weight (weight savings) from the back of my trans. He said that was for vibration dampening. I found the bracket but tossed the rubber isolation weight. It was about the size of a large soup can. Anyone have an idea on fabricating one or other solution for dampening?
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I have never seen a set up like that, got any pic's?
 
Couldn't find a picture online. Will check shop manual when I get home.

Grainger shows something similar. Can shaped piece of rubber with a bolt sticking out of it. Was about 5 pounds if I recall correctly.

I'm sure balancing the driveshaft would cure the vibration but I have a A500/A518 plan for the near future. Will need a new driveshaft.
 
Its odd, as lots of people have tossed those weights without any ill effects. Especially the big cast iron one saddled around tailstock.
 
Been a little while but have an update. Drivetrain still has vibration. Was at a "tolerable" place above 65 so didn't bother me much but really feel it at highway speeds and need to put this to sleep. I recently replaced my trans mount bushing with a polyurethane type and the vibration got/felt much worse at lower speeds from about 50mph and up. My next step is to place the car on jack stands and run it while underneath the car. Not looking forward to this. The vibration is not steady. It oscillates in sound at steady rpm/speed and occurs under load. 8.25 Rear.
Here is a rehash.....

Appears to have started after installing 3.55 gears and sure grip with unused parts. Also added crush sleeve eliminator.

Rechecked mesh pattern and pinion turns freely and smoothly. Both good. Wear good. Replaced fluid. Yes anti slip additive.
Checked driveshaft orientation.
Found bad front u-joint. Bingo. Replaced. No change. Also replaced rear u-joint.
Tried checking driveshaft balance using 2 hose clamps in 4 different positions 90 degrees apart. No change. Weights are in place.
Swapped used rubber trans mount with another used trans mount and then poly mount. Vibration rpm feel changes and has been noticeable anywhere from 45 mph to 70 mph.

What am I missing???
 
JoePole1 said:
Been a little while but have an update. Drivetrain still has vibration. Was at a "tolerable" place above 65 so didn't bother me much but really feel it at highway speeds and need to put this to sleep. I recently replaced my trans mount bushing with a polyurethane type and the vibration got/felt much worse at lower speeds from about 50mph and up. My next step is to place the car on jack stands and run it while underneath the car. Not looking forward to this. The vibration is not steady. It oscillates in sound at steady rpm/speed and occurs under load. 8.25 Rear.
Here is a rehash.....

Appears to have started after installing 3.55 gears and sure grip with unused parts. Also added crush sleeve eliminator.

Rechecked mesh pattern and pinion turns freely and smoothly. Both good. Wear good. Replaced fluid. Yes anti slip additive.
Checked driveshaft orientation.
Found bad front u-joint. Bingo. Replaced. No change. Also replaced rear u-joint.
Tried checking driveshaft balance using 2 hose clamps in 4 different positions 90 degrees apart. No change. Weights are in place.
Swapped used rubber trans mount with another used trans mount and then poly mount. Vibration rpm feel changes and has been noticeable anywhere from 45 mph to 70 mph.
I just live with the 10%.
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I had a driveshaft that drove me nuts. Had it to the local shaft shop twice they swore there was nothing wrong. Took it to a different shop and they found that the driveshaft was in balance but that the tube was badly out of round so they replaced the entire tube and the beat up rear yoke and the vibration was 90% gone. I just live with the 10%.
 
512Stroker said:
I had a driveshaft that drove me nuts. Had it to the local shaft shop twice they swore there was nothing wrong. Took it to a different shop and they found that the driveshaft was in balance but that the tube was badly out of round so they replaced the entire tube and the beat up rear yoke and the vibration was 90% gone. I just live with the 10%.
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Thought about that. I will check for runout from under car.
 
JoePole1 said:
Not sure but wouldn't that happen at all speeds and even neutral if say weight came off?
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Maybe not ALL speeds, but yes you would think that it would be replicated in neutral. Sorry I missed the post that took that one off the list. Only when driving....copy that.
 
So are the axles nice and smooth where the bearings are. If not u can get a repair bearing from Napa that is wider and moves the rollers on to the undamaged part of the axle. Kim
 
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