Fire-formula 93

iTrader: (1)

It is driving me nuts. When I first bought my car, it had no vibration on the highway at all. I installed a rebuilt rear with 4.10s and I think that is when the vibration started. Right at about 60 mph and faster is where the vibration occurs.

Since then, I have bought all new wheels with 2 new tires (other 2 were transfered from old wheels), the vibration stayed the same like it should have.

I have also put the stock rear end back in and the vibration stayed the same. I know the driveshaft is supposed to be in balance with the pinion yoke so I remove the driveshaft from the pinion yoke, flipped it 180* and bolted it back together. Vibration is still the same.

So the only thing left to blame is the driveshaft right? But how would that go out of balance on its own?

As stated the vibration starts right at 60 mph. There are some speeds above 60 that has less vibration, 64 mph seems to be the worst though. I can feel the vibration in the steering wheel only sometimes which really confuses me. Any help is very much appreciated, this is really bugging the hell out of me.

JD_AMG

Do you have stock brake rotors? They may be warped, get some duralast or brembo blanks at autozone for cheap, they wont warp.

TORCHD 02 TA

iTrader: (39)

i think that the DS is out of balance and will need to be re-balanced or your rear is not straight. What i mean is you may need get an adjsutable TQ arm and get a pinion angel finder and adjsut the pinion agnel

SoCalZ28

iTrader: (10)

I agree

Fire-formula 93

iTrader: (1)

Why would my pinion angle be off though? The car is not lowered or anything.

I was thinking about the rotors being bad. They do pulsate when braking at high speeds.

yekta

iTrader: (8)

discs warped = vibrate only when u brake

perhaps u remember wrong, and they couldn't balance your tires when u changed

trackbird

iTrader: (4)

Is it a steel driveshaft?

Driveshafts have a "critical speed" where they can potentially fail due to rpm. The stock steel shafts have a lower critical speed than the aluminum ones. Where this gets important is that at 1/2 of critical speed, strange vibrations and resonances can take place. So, if you have a driveshaft that's only good to 120 mph with 4.10 gears (driveshaft RPM is the key, the steeper gears just lower the speed that you reach that rpm with the driveshaft), you'll start getting vibrations at 1/2 that speed. And, off the top of my head, I didn't think the steel shaft was good for much over 120 (not that they will all fail "instantly", but they could fail at that rpm) with 4.10's. The LS1 aluminum shaft is good for something in the mid to upper 160's with 3.42's (as I remember). Again, this is a rating based on diameter, material, wall thickness and length, they calculate where the driveshaft will resonate and calculate the RPM that can set up that resonance (which could lead to failure).

Or, you might have a twisted driveshaft. After many launches, the stock driveshaft can start to twist and not return to shape after each launch (aluminum and steel driveshafts can both do this). You can eventually put enough stress on the driveshaft to twist it slightly. Once it's twisted, the u-joints will be out of phase and will bind slightly, this can result in a vibration at certain speeds.

I'm going to suspect it's a driveshaft issue. My 1989 Formula had a nasty vibration (from 60-85) for a year or so (until I swapped the driveshaft), and when I finally changed the steel driveshaft to a new aluminum driveshaft, it was gone. I don't know if mine was bent or twisted or just not straight, but it was one of the three.

I'd get that driveshaft checked out.

Edit: I'm speaking of the stock steel driveshafts, the aftermarket nitrous shafts and such will have a much different critical speed and I don't want anyone thinking they need aluminum for a higher critical speed, it can be done with a properly designed steel driveshaft as well.

yekta

iTrader: (8)

I think he is driving a 02 WS6, gotto be aliminium

TORCHD 02 TA

iTrader: (39)

it could be off from who ever set the ring and pinon.. a pinion angle wil find that.. i think if i am not mistaken you want it a -3

JD_AMG

Does your steering wheel shimmy?
Its your brakes man, I had warped rotors, and they do vibrate the car no matter if I was braking or not. Changed them and problem solved.

TORCHD 02 TA

iTrader: (39)

it is not the brakes. it vibrates at 60 mph. he was not hitting the brakes.... my buddies LT1 did that too. it was a combo of DS, and TA

trackbird

iTrader: (4)

-3 is pretty aggressive. If you get it angled too far down, you'll bind the u-joints and that also can cause a vibration. I'd try to stay at or under -2 for a street car to avoid u-joint wear issues.

JD_AMG

I just said I had the same problem witout touching the brakes(around 50-60mph, then comes back around 80). Warped rotors will vibrate the car even when your not braking, my car was living proof.

Fire-formula 93

iTrader: (1)

Thanks for all the help guys.

I do get the steering wheel shimmy sometimes, not all of the time that the vibration is occuring.

Remember, the stock rear is back on, so pinion angle should not have changed from when I first got the car.

It is really hard to tell if the brakes are warped, sometimes I feel the pulsating in the pedal, sometimes I dont. When I do feel it, it is fairly minimal.

First, I think I am going to take the DS off of my moms TA and put it on my car and see if it makes any difference. If there is no difference I will get some Duralast rotors. If there is no difference after that, I will look into an adjustable TA. I just dont think pinion angle is my problem.

Oh one thing I forgot, I might replace the energy suspension Tranny mount too, I heard that can cause a vibration.

trackbird

iTrader: (4)

It can cause a fair amount of vibration, based on my experience.

98boxer

iTrader: (7)

Isnt the energy suspention tranny mount made out of polyurethane? I belive it is, and this is one cause of your vibrations, im assuming you just got the energy mount put on. Well happens after a while the poly tranny mount doesn't cause as much rattles. After i put on my poly tranny mount, high way runs were loud with a lot of vibration especially when in 3rd. But now, i don't have the vibration i used to have at first, so i belive after awhile the poly mount will eventually cushion the vibrations.

Fire-formula 93

iTrader: (1)

Yeah the tranny mount was on my car when I bought it.

Hey JD_AMG, When you had the vibration from your brakes, how bad was the pedal pulsating when you did brake? Like I said before, it is really hard to tell if it is my brakes that are vibrating.

JD_AMG

I dont really remeber my pedal pulsating, but rather the whole car would 'wobble' when I braked, and the steering wheel would shimmey more than if I wasnt braking. Got the rotors turned, then about 2 weeks later it came back, and I wasnt braking any harder than I would be in any other car.
Either way the stock brakes are pretty much crap, and will warp eventually, so getting new ones should be on the top of the list anyway. If I ever buy another F-body, thats the first thing thats going to be replaced.

TORCHD 02 TA

iTrader: (39)

thanks for the confirmation i just was not too sure..

ramairracer

iTrader: (13)

in my overall experince in dealing with these cars i noticed that like guy mentioned alrady the brake rotrs tend warp rather quick may be from running over a puddle while they are hot.. or it may just be a simple thing that occured on its own. Either way my first step would be to install NEW rotors the ones you have on your car have more than likely already been turned too many times. when handling new rotors make sure not to letANY grease touch them because they will warp really quickly. My first thought when i read this post was that whoever messed with you diff. probably didnt scribe the pinion flange to the housing, but since you reinstalled the stock diff. then thats not it. Typically our driveshafts tend not to loose balance unless they are removed or added .. another question to ask is that are your tires all the same i.e. tread and brand, more importantly are some directional biaised while another ir normal if so thats the problem, and are you certain that they were balanced correctly i dont know how many times ive seen people go to other shops and get them "balanced" only to find they are off, some places tell you its done without do it correctly to simply get you in and out..
try what ive said and im 99 perecent sure thats the problem