stangkillin99ss

Guys i am at my wits end with this car, i badly need your help. I am having a horrible vibration at moderate to high speed. The car has a moser 12bolt spohn tq arm, dennys driveshaft, and built t56. For a while now i have had a horrible vibration, i thought it was the clutch so i changed it, nothing, brakes, nothing. Heres what happens at about 50 up i get a vibration that gets worse the faster i go. HIt 90 and it feels like the car is going to come apart! if i let off the gas it gets worse as oppose to giving it a little throttle but it is still very bad. Also when i shift the hard car sounds like something is banging up under it.

For the vibration everyone says Drive shaft, but i have tried 2 different ones, same out come still vibrates like hell. I called moser and they said its IMPOSSIBLE for the vibration to be coming from the gears...but i dunno if thats true.

I put the car up on a lift and drove it to 90mph did get it to vibrate like it was before.

WHAT COULD THIS BE?? PLEASE HELP ME!

ErikElvis

iTrader: (1)

Does it wobble the steering wheel? or does it feel isolated to the rear? Did you check all of your mounts ie: engine/tranny?

02Z28LS1

iTrader: (2)

if it doesn't have any vibration when the rear wheels are up in the air, it's likely not a problem with the driveshaft, rear end, or wheels/tires.

in that case, it sounds more like something to do with the front wheels/tires/suspension.....especially if the steering wheel vibrates too.

one thing you can do is swap the front wheels to the back with it off the ground and run it to 90 again....if it starts vibrating then, get your wheels re-balanced. if it still vibrates after that, have the rims checked....they may be bent.

if there's still no vibration after the swap, you need to start looking at the front suspension components.....bushings/tierods/shocks/a-arms/etc.

stangkillin99ss

the transmission mount has been swapped to the 1LE and new engine mounts have been put on. As for the wheels and tires they have been balanced and rebalanced even new tires put on. There is some vibration but nothing to write home about with it on the lift at 90mph. the steering wheels vibrates a little but nothing like ive seen with cars that have alignment issues. even though i "think" its coming from the rear, could it possibly be the front end? I mean this thing really sounds bad at high speed!

The sophn did bang a hole in my floor board under the tunnel from the damn thing hitting. I have checked and re checked the pinion angle and tried everything from +5 to -5* with no avail.

any other ideas?

I too thought it may be a problem with the shocks so i installed a set of HAL QA-1 Full coil overs front and rear, didnt help

stangkillin99ss

ok i spoke with steve at spohn and he said that it is the TA contacting the body when the suspension is compressed at highway speeds. I am going to have to cut a hole in the body to allow the TA room to move through its range of motion without touching, this should solve my problem, i will keep you guys posted.

02Z28LS1

iTrader: (2)

instead of drilling a hole, you may want to try using a BFH first to just pound on the bottom of the car a bit where the T/A is touching....it may be enough to do the trick.

by now, you should be able to see all the places it's hitting, since the paint should be scraped away.

stangkillin99ss

ok i did the deed and got out the cutting wheel and cut out where the TA was hitting. drove on the highway same ****...however i put it back up on the lift and drove it in the air, it definatly is doing it while on the lift. vibrates like crazy at 80mph up....could i possibly have had 2 bad driveshafts, one from dennys and one stock? or could it be somewhere in the transmission or even the gears on the rear end?

BarneyMobile

iTrader: (4)

I can only think of two things causing what you describe. I'd set my pinion angle to -2 degrees and see if that takes care of the problem. I'd also check the drive shaft U-joints. I had in issues with my LT1 camaro where I had a bad vibration at 70+ mph. Turned out to be bad u-joints.

cam

iTrader: (9)

I'd try another set of wheels off a friends car that you know are smooth. Vibrations are a bitch to solve and I've been foiled by a "balanced" wheel and tire before those machines dont always reflect what happens at speed when things go weird

Jimmard

iTrader: (12)

I'm having the same issue. Here's what I have done so far, you should try the same.

First I jacked the car up by the rear axle, so that the suspension was still compressed, and got it up to speed, vibration was still there. Pulled the wheels and tires off, ran it again, still there. Pulled the calipers and rotors off, ran it again, still there. Put in brand new driveshaft, ran it again, still there. Adjusted the torque arm in 1* increments from +4* to -4* and ran each time, didnt help at all. Last thing I can do is to replace the bushing in the tailhousing of the transmission because the stock ones sometimes break loose and spin, causing uneven wear and a vibration. I just have to order the parts up.

CW00BlackTA

iTrader: (31)

I'm going to say your problems are related to either pinion angle, pinion yoke or u-joints. I've been through all of this with mine and have done the same things you've tried. I had a bad pinion yoke with excessive runout. Changed that and much of the vibration went away. Get a dial indicator with a magnetic base and check yours. I had to adjust my pinion angle to 0 to -1/2 degree to minimize vibration--it has to be exact. I also had tried the one degree increments without success. Try it again in half degree increments between +/-1 degree. Finally, if your pinion is off by much, it will eat your u-joints in a hurry. Change your rear u-joint when you check the rest of this to eliminate that variable. Finally, I also put 1/2 rubber spacers where my Spohn TA mounts to the body and did the BFH mod to make room for the TA in the back. Do all of this and a Ford 9 rear with Spohn body mount torque arm on a lowered Trans Am will be almost (but not quite) as smooth as the factory set-up.

stangkillin99ss

How will i know if the pinion yolk is bad? I just took the driveshaft off and sent it back to dennys for testing. We'll see what happens. Right now im at a point where i cant do much because im driveshaft less and the stock one no longer fits with my Viper t56. I have changed the ujoints out, that wasnt it though.

RAGENZ28

iTrader: (5)

Never set the pinion angle at 0* you'll screw up the u-joints

Some place between -1 to -3 is where our cars should generally be set at, if it is vibrating at -2* changing it -1* isn't going to do much because it shouldn't be vibrating at that pinion angle anyways.

Vibration can be from a lot of things be more than likely it is incorrect pinion angle, loose or incorrectly installed suspension parts, play in the pinion yoke, bad u-joints, drive shaft isn't balanced right, bad tires, bad alignment or front suspension parts, trans shaft play.

There is a lot all you can do is check one at a time. If you're getting vibration in the steering wheel normally you'll want to look for things up front first.

A bad drive shaft or gears you'll mostly feel and hear the vibration but not really in the steering wheel.

Also check the wheel base, not sure if you have adjustable control arms or not, but if the wheel base is off that will cause vibration too, especially at high speed.