Pedal-2-Metal

Ok... I have read all posts and cant get this. Some say pinion up some say down??? Some say check by driveshaft some say tranny/motor angle???
I would assume to check by the angle of the tranny since you want the u-joints to be parallel. so I have no clue why the driveshaft would come to play here.

I have adjsuted pinion angle up 2 deg, up 4 deg, down 2 deg, and zero'd it out with NO luck. at 85-90 mph vibraition hits me.

I have the Spohn adjustable solid joint cross member mount T/A.

I was told that there are places whom can put the vehicle on a laser adjusted frame rack and have it adjusted??? Any knowledge on that?

Thanks...

Pedal-2-Metal

ok... thanks

Pedal-2-Metal

anyone.. i had it taken to a place and he put it at -2. but at 90mph still SONS of vibration. any help

Squintz Palladoris

iTrader: (1)

What kind of transmission mount are you running? When did the vibration start?

Brad

JRcamaroZ28

iTrader: (41)

have you had your tires balanced? i ask this cause i was having problems w/ vibration no matter what angle i was at. After I had them balanced the problems went away soon as i got the angle dialed in close. now i just need to work on getting it fine tuned for best traction.

JR

Pedal-2-Metal

I have a poly mount. which i know my car is stiff as hell! 6 pont roll cage, subframes, spohn solid crossmember T/A, air bags in rear springs, 4.10's...

My tires where balanced before i had the T/A added. I had no vibration then?

My rear end pinion as in the actual "PINION" is -2.5... The place I took it to said that he never like rear ends pointing up, but I am guessing he has had more work on leaf spring vehicles rather than coil spring'd T/A mounted stiff A$$ f'ers like mine!

any ideas???

Pedal-2-Metal

help... anyone?

Do you think not having an ADJ Panhard bar could cause something with me rear off center?

Squintz Palladoris

iTrader: (1)

I would say it is the poly tranny mount causing this vibration. I have one in my car and it does the same thing. Try putting the stock one back in and see if the problem is still there.

Brad

Pedal-2-Metal

i give up! thanks

WAHUSKER

iTrader: (4)

This is what I was told.....and how mine is setup with NO vibration & good traction.

Down angle = better traction, too far down = noise (& vibration?).

Measure the drive shaft & compare against that (it is what connects to the pinion, and it's almost parallel to the tranny anyway). You want somewhere around -2*.

Sounds like you might have another issue tho. Vibrations means something is out of balance. Drive shaft, tires, something....hard to imagine your angle is that far off.

As for the pan hard bar, that will center the back tires under the car, but should at worst cause a little dog-tracking, not vibrations.

Hope this helps some.....
Mark

Dustin Butts

iTrader: (5)

First I'm guessing you have an M6 and a 3.42 gear..correct? If so, then you're probably going to have to live with the vibe. I, like you, had the same problem and studied and thought and studied and finally realized that it has to do with some type of weird harmonics in 6th gear. The rear end gear/driveshaft speed is so much more than the engine it cause a weird vibe at that speed(80-90mph). When you start modifying and adding poly mounts and such it gets much more noticable.
If you want you can add a 4.11 gear and then you'll be much happier in 6th gear because at the comfy cruise rpm of 2200ish you'll only be doing about 80mph instead of 90mph with the 3.42 and the vibe will be gone. The 4.11 gear will help save you some speeding tickets on the interstate because of this also.
It will also make your car a bit quicker at the track.
If you have only around 400hp or so and are mostly street, then set the pinion angle at about -2 or -3, just measured straight off the bottom of the diff and you'll be fine.
If you drag race alot with slicks you could experiment with a couple more degrees down and see if your ET's improve.

CHRISPY

If he measured it just from the pinion then you are probably running a total of -4 to -5 degrees pinion angle. The tranny angle is typically 88 degrees or -2. If you want the pinion angle (true pinion angle) to be -3 you need to put the pinion to -1 degree.

I bet it is a little bit off but not much. Is the poly tranny mount the same thickness as stock? If not that'll throw off the calcs and you'll need to pull the DS to actually test it.