Stock 86, High Speed Vibration

Posted By: guitars

Stock 86, High Speed Vibration - 05/10/22 12:04 AM

At speeds above 55 MPH I feel a buzzing and hear the dome light vibrating. Here is what has been checked.
1. wheels rebalanced
2 off ground testing with weight on rear axle, wheels removed, brake drums removed = rear axle vibration
3.driveshaft u joints checked for movement -ok, - rear of driveshaft at pinion shaft= no runout, at pinion bearing=no play
4. front of driveshaft has little play in transmission output bushing, seal and bushing 1000 miles old- no leak
5 left axle bearing has very little play, right axle bearing a bit more play and a little runout(plus a very slight wobble)
6.right axle shows more c clip wear in-out movement

Summary - the vibration is felt at both ends of the axle housing equally but not as pronounced at pinion bearing end, This is an axle without wheels and brake drums for testing.

Will measure axle shaft at bearing diameter and check for bearing wear surface
Would the driveshaft u joint angles need to be verified?
Is there anything I missed
1986 SS, 90k miles, no accidents, always had vibration since I bought it about 8k miles ago
Thanks, in south eastern Ontario
Posted By: Buick Runner

Re: Stock 86, High Speed Vibration - 05/10/22 12:36 AM

Did you check the driveshaft for balance? That includes clocking it to the same position it was removed from.
Posted By: AkronAero

Re: Stock 86, High Speed Vibration - 05/10/22 01:01 AM

X2 on Buick's balance check.

Also note that apparently MANY shops will replace a bad bearing cap assembly rather than change out the entire U-Joint. Sort of makes sense except not all bearing caps are interchangeable. As I mentioned in an earlier thread, my driveline shop finds several mis-matched bearing caps each week. I believe the outer bearing cap diameters are the same but the inner/bearing dimensions are not. I had an earlier shop build a NEW drive shaft for me and they mis-matched parts using different vendors. Took it back to rebalance and it still vibrated. Kept welding on washers to try to correct. Thus the stop at a pro shop where they put the yoke in a vice and twisted the other side all over the place. Inspect the u-joints for play (may not see when mounted?) and if any doubt swap them out for a new set (not expensive).

Good hunting and let us know.
. .
Posted By: 86ttop

Re: Stock 86, High Speed Vibration - 05/10/22 01:24 AM

Try this, I know, you're gonna think it's goofy, but an old time mechanic told me to put a hose clamp on the driveshaft at the rear u joint and mark the positions at the caps as 1-2-3-4 and spin it just as you already did and if the vibration is still there, move the hose clamp 1/4 turn,to the next mark and retry, if that takes care of it, you're good, if not, try the next position and so forth! Good luck and let us know how it turns out!
Posted By: guitars

Re: Stock 86, High Speed Vibration - 05/11/22 01:29 AM

It looks like the driveshaft yokes are welded off center causing oscillation at either end and the middle - 25 -30 thou. It's visually easy to see if the shaft is spinning. I checked all u joints - no looseness, C clips firmly seated, u joints check good, no missing internal spacer in bearing cups, no pinion/companion flange runout or looseness, Not sure if I have enough hose clamps to offset the wobble.
Posted By: 86ttop

Re: Stock 86, High Speed Vibration - 05/12/22 01:05 AM

Use just one large enough to fit around the driveshaft and see how it works, good luck!!
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