high speed vibration

injdinjn

Active Member
#1
My 86 GP has a high speed vibration. about 82 it becomes noticeable and about 87 it maxes out and stays that bad up to 130, i havent had it any faster.
This has been here thru 3 sets of tires and 2 sets of rims and a performance alignment. And thru a ring and pinion change. Bilstiens all around and for awhile QA-1s (junk) on the back.
No vibration thru the steering wheel
It has been suggested drive shaft (factory) and exhaust hitting the frame. Any ideas on what it could be or the best way to diagnose it.
Thanks
 

injdinjn

Active Member
#3
No, I just replaced the trans and one u joint was bad. Replaced it and no change.
The LCRs are boxed and all the rear bushings were replaced when we changed the rear end gears.

Nice try, reminded me of things I did replace and forgot to mention.
 

charlief1

Just another kinky six
#5
Have you tried a road force balance? You could also have an out of balance driveshaft. Does it feel like it's in the seat or all over?
 

injdinjn

Active Member
#6
No poly anywhere

Whats a road force balance.
Drive shaft was suggested, esp since these cars were anemic and high power was never in their planning. I did mention it to a drive shaft builder and he didnt think the driveshaft was the problem. I have one in another G body. I guess my next test would be to swap drive shafts.

Vibration is all over, first thing you notice is the inside rear view mirror vibrating, then the whole car. Since the steering wheel doesnt vibrate that eliminates anything in the front suspension i would think.
 

charlief1

Just another kinky six
#8
No poly anywhere

Whats a road force balance.
Drive shaft was suggested, esp since these cars were anemic and high power was never in their planning. I did mention it to a drive shaft builder and he didnt think the driveshaft was the problem. I have one in another G body. I guess my next test would be to swap drive shafts.

Vibration is all over, first thing you notice is the inside rear view mirror vibrating, then the whole car. Since the steering wheel doesnt vibrate that eliminates anything in the front suspension i would think.
Road force looks like a normal balancer but has a wheel on the back. It puts pressure on the wheel as it spins to check for imperfections. Makes for an almost perfect balance.

With the vibration all over I'd say something is up with the driveline and not the supension.
 

injdinjn

Active Member
#9
Road force, Ok i know what those are, havent seen one in years.

When I had the trans out the front ujoint felt good, but the back was notchy so we replaced it. Worth checking the new one, God knows where this $hit is made anymore.

My son/crewchief has been pushing for a aluminum one for a couple of years now.
 
#11
I had a similar problem w/ mine. Turned out to be one very badly and one slightly bent axle.
I no this is old but I wonder if he ever found the problem? I have the same issue and I am starting to think it's my brand new moser 30 spline axles I installed a new eaton
Locker with new ring and pinion
All new bearing? Starts around 65
And seems to get better around 80
But is still there? Are the drive shafts indexed? I also installed new
U-Joints
 
#12
I no this is old but I wonder if he ever found the problem? I have the same issue and I am starting to think it's my brand new moser 30 spline axles I installed a new eaton
Locker with new ring and pinion
All new bearing? Starts around 65
And seems to get better around 80
But is still there? Are the drive shafts indexed? I also installed new
U-Joints
Also could it be The torque converter?
 

Chuck Leeper

Waay too old!
Staff member
#15
Short of breaking at the joints, many d/s failures are due to repeatedly exceeding the critical rpm. This causes the shaft to "whip". The shaft stress is concentrated in the center area. Have the shaft checked to see if it has excessive run out in the middle.
 
#20
Short of breaking at the joints, many d/s failures are due to repeatedly exceeding the critical rpm. This causes the shaft to "whip". The shaft stress is concentrated in the center area. Have the shaft checked to see if it has excessive run out in the middle.
This was the cause of vibration in one of my cars. The shop was able to straighten it.

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