I'm looking for some ideas here. There is a vibration in my '84 Monte SS that I think is driveline related. It starts at about 85-90km/hr (about 50mph), and I can drive out of it at about 100km/hr (about 60-65mph). The car has a 3.42/1 rear axle gear, and the turbo 350C transmission (no overdrive). The vibration feels like its in the car, not in the steering. The driveline is original in the car, and the car has 119,000kms on it (about 75,000 mi). I've tried a couple of different driveshafts in it, even having the driveshaft balanced, and it hasn't made a difference. I remember reading about someone talking about the bushing in the tailshaft of the transmission causing this type of vibration if its worn, but I don't know if this is the problem with my car. Its not a really big concern, because I don't drive the car much, but it is kind of annoying. Anyone have any thoughts or ideas? Thanks in advance.
Vibration problem
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have you had the tires balanced? after that, check the pinion angles, especially if the springs are sagging/ you have lowering springs. also, check the rear control arms, you want to do this with the wheels in the air, and on the ground.
Megaladon, to answer your questions, yes, the wheels have been balanced. I installed lowering springs on the car years ago, but if my memory serves, the vibration was there prior to installing the lowering springs. The springs that I installed lowered the car by 1" (I just wanted it down a bit). With the exception of the springs and shocks and the front sway bar bushings, the suspension parts in the car are all original (my parents bought the car new, and I've owned it since 1988).
PontiacGP, the pitman arm is original.
If you guys could fill me in a bit on your reasoning, that would be helpful.
Megaladon, I've seen these cars that had sagging springs, so that they sat lower than mine, without any vibration. What puzzles me is that this vibration seems to only occur in a fairly narrow speed range, which leads me to believe that it is driveline related (possibly transmission output shaft speed related?).
Just to add, I've installed 16" IROC rims with P235/60R16 tires, but like I've said, the wheels have been balanced.
Thanks again for your help.
PontiacGP, the pitman arm is original.
If you guys could fill me in a bit on your reasoning, that would be helpful.
Megaladon, I've seen these cars that had sagging springs, so that they sat lower than mine, without any vibration. What puzzles me is that this vibration seems to only occur in a fairly narrow speed range, which leads me to believe that it is driveline related (possibly transmission output shaft speed related?).
Just to add, I've installed 16" IROC rims with P235/60R16 tires, but like I've said, the wheels have been balanced.
Thanks again for your help.
you should still check the pinion angle, it could have been off before. it's known for creating a narrow band of vibration in the rear. worn/cracked rear bushings can cause the same thing, partially for the same reason.
PontiacGP, the idler arm was replaced with a Moog part years ago, and its in good shape. thanks for your input though.
Megaladon, thanks also for your help. I'm starting to understand what you're saying. I didn't think that the pinion angle could be far enough out to cause this condition, but its worth checking. I guess that worn suspension bushings could also be a culprit.
Thanks again.
Megaladon, thanks also for your help. I'm starting to understand what you're saying. I didn't think that the pinion angle could be far enough out to cause this condition, but its worth checking. I guess that worn suspension bushings could also be a culprit.
Thanks again.
FWIW, it only takes a fraction of an inch to change the pinion angle. i have the same problem at about 90mph
when I get a vibration that I can't find I put the rear of the rear of the car up on jack stands placed under the frame. Then I run the car at at the speed where the vibration is felt and if the vibration appears you may be able to see where it's coming from. If it doesn't appear then I start jacking up the pumpkin with the car still running until the vibration appears and then take a look to see where it's coming from. If it still doesn't show up then I know it's in the front end...
the other think like already mentioned it could be a wheel unbalanced....even if you just got them done one could have thrown a weight or it could have been done incorrectly or the machine they used was malfunctioning
the other think like already mentioned it could be a wheel unbalanced....even if you just got them done one could have thrown a weight or it could have been done incorrectly or the machine they used was malfunctioning
I ran into same problem in my 98 tahoe. Check the rear end make sure its full with good fluid. Mine was only bout 1/8 inch low on fluid n was causing a slight vibration from 45 to 60 then again at 85+. It was last thing I checked n was more of a prayer than knowledge.
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