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Originally Posted by HWYSTR455
Oh yeah, duh on the different part numbers! Ok, strike one against me!
I'm curious about this latest topic, and really want to hear other's input too. I just disassembled my entire cutlass rear suspension, wish I would have taken all the measurements prior, and compared the uppers with the aftermarket ones. My LeMans has GW uppers I believe, and it doesn't have any vibration issue, and I've topped that thing out many times. I did have a pinion bearing go bad due to a yoke 'nub' being worn, and the u-joint not seating right, which vibrated and took out the bearing. Aside from that, no vibration though.
Explain the vibration? Specific speed range, or above a certain speed? And it's not RPM related?
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I am open to hearing from anyone that wants to comment on this issue. The vibration occurs at high speed. It starts at about 75 mph and down not go away as you go faster. It is dependent on the driveline speed, not engine speed. In other words it will occur in any gear that will go to that speed and is also present if you pop it into neutral. By those symptoms the vibration is in the driveline, most likely the driveshaft. This vibration has been present with two engines, two sets of tires, three driveshafts, two pinion yokes (the latest pinion yoke made it a little better), two front brake systems, and two rear end assemblies. The other clue that tells me that it is related to the driveshaft speed is the fact that the vibration moved in the MPH range when I switched rear ends. The first rear had a 3.31 gear and now it has a 3.73 gear. When I went to the 3.73 gear the vibration started to occur at a lower MPH (but same driveshaft speed) as before.
I had a lengthy conversation about this with Frank at the Driveshaft Shop. He is a good guy and I have dealt with him on some custom axles for my RX7. He just got a new high speed balancing machine and has been doing a lot of work with several NASCAR teams. He seems to believe that a material change is in order to bring the weight of the driveshaft down. Stock a-body driveshafts are about 2.5" in diameter and are fairly light. Even though I have gone through three different driveshafts they have all been 3.5" mild steel, and pretty heavy. Frank believes that going to an aluminum shaft will solve the problem and a carbon shaft would be even better.
As I said, I am all ears if anyone else has comments or suggestions.
Andrew