BlackMage

put 4.10's in about 5 years ago, had vibrations from the driveshaft once you hit about 70. put in a windstar aluminum d/s and got rid of the vibration. this past week i put in upper and lower rear tubular control arms with poly bushings. Right after I did that i have a decently bad vibration once i hit about 50mph, and only gets worse from that speed on up. If i push in the clutch, or put the trans in the neutral, the vibration stays, does not go away. I can feel it the worst when im about 5%-25% throttle. I pulled the rear diff out thinking the pinion bearings were shot, and checked all the bearings and everything seems to be fine in there. I also changed the wheels to a different set and still have vibrations. Any other ideas what might be causing the vibrations?

Shampue

did you just change the rubber or the wheel too? I have a small bend on one of my wheels right now (previous owner issue) and I only get the shakes at certain mph

BlackMage

No, i put a whole different set of rims and tires on. Vibration was still there :-/

Shampue

front brake loose?

/straws

cliffyk

Polyurethane bushings...

TRexGAWD

I can't imagine that causing a specific speed vibration.. I can see it making it feel worse but, causing it at 50+, I dunno...

Sure you installed the control arms correctly, were they adjustable control arms?

BlackMage

that was a thought of mine, so i pulled an upper and a lower to compare to the stock arms and they are the same lenghts, and no they are not adjustable.

the only other thought is that maybe the vibration has always been there but the rubber bushings absorbed almost all the vibration and then the poly's just amplified it like Cliffy stated?

cliffyk

I have never been a fan of polyurethane bushings on any street car, unless the owner is willing to deal with the increased NVH--at time greatly increased, you would be amazed at some of the back-to-back comparisons I have done and participated in over the years.

They are a lot cheaper to make than the moulded synthetic rubber units used by automakers, which would save the manufacturers a slug of money, but they don't use them because they would be a complete turn-off for 99.44% of new car buyers...