Maybe you guys can help me, this is going to be VERY hard to explain on here but I will try

As I am driving the car is vibrating, it's not like a tire is out of balance though, if so it should be constant... My vibration is RYTHMIC! Here is the funny part, I feel a vibration in my ass, then in my hands but not my ass.. The Vibration starts at the BACK of the car and rolls forward the vibration "Wave" lasts about 1 second, then 1 secnd off then another WAVE... It only happens ABOVE 100 klms (60mph).... It just feels weird (and it happens on any highway so it's not the road I am on)

Wheel Alignment!

here, here!

quote Originally posted by Wolfhound: Wheel Alignment!

Are you sure? I do'nt see how wheel alignment could cause that....

Excesive front toe in or toe out will cause the tire to distort as it tries to take a nonparrallel path and then correct it,s self. this is the viberation you feel.
This can happen also with the rear but you mentioned that you feel it in the steering ,so it,s likly the front.

quote Originally posted by Wolfhound: Excesive front toe in or toe out will cause the tire to distort as it tries to take a nonparrallel path and then correct it,s self. this is the viberation you feel. This can happen also with the rear but you mentioned that you feel it in the steering ,so it,s likly the front.

But it's a ROLLING wave of vibratoin that starts in the rear I feel it BEHIND me then it moves forward and i feel in in the wheel and in front but NOT in the rear at that point....

Pretty Sure! You have lost your alignment for some reason. Pothole , Worn steering parts or something? I can't be sure the exact cause without checking it myself but thats pretty much it . Are your lug nuts tight?

Two tires out of balance and resonanting. Since they are not exactly the same, they go in and out. About a 3 second period right? Worse at three places? 35, 70 , 105-ish?

If so, have them spun on the car.

Grinthock,
I have the almost the same problem. I noticed it when I got a new set of tires. Had them rebalanced 3 times and got pissed off at having to go back for the same trouble over and over and..... Just figured I bought a set of duds that were out of round. Just makes me want to stop by the bar, have a brew and play Elvis' Shake Rattle & Roll. I hate having to stand over someone and point out the trouble when I pay them for that service and knowledge. The shop I went to is the last tire shop in this area that hasn't screwed me and I think they going to turn out like the rest. Seems the tire monkeys around hear don't give a **** about your vehicle unless it's new. If it's over 10 years old they want to tell you its wore out and probally will never be right again no matter how many new parts you put on. Well BULLSHIT, I probally ought to know better than dealing with people that thinks you have to be a rocket scientist to put a v8 sideways in a car. Anybody Know of a real tire shop close to West Tennessee where a man can get a new set of tires that don't reverberate "dumbass me" down the road? I would sure would appreciate the tip before this set of tires I got really do damage some parts. And thanks guys, I will recheck my alinement before I give this last tire monkey a cuss'in.

You should go somewhere good and get a 4 wheel alignment and have all 4 tires spin balanced. If that doesn't cure it, check wheel bearings. If that doesn't cure it, I'd bet the frame had been racked. Hope you figger it out.

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Sounds almost similar to a twin engine plane with the props out of sync, the vibration will travel in rhythms as the shock wave off the tips vary as they hit the sides of the fuselage.
Tires with different tread patterns can do that, as can tires with different heights.

The few times I have flown my Fiero it did not handle at all like an airplane, but your description of the sound struck a chord.

Anything out of balance can cuase it.

check the hubs for play.

check the half shafts for slop or damage.

definatly check wheel balance. BEFORE you take it for rebalance, take the wheels off and make sure the back/interior side of the rim is free of dirt buildup and stickon weights. Most wheel guys don't check for stickons and try to balance with them still stuck in there. If you picked up a wad of mud or had a wad break loose after balance you'll also have problems....

Also check the cradel bushings on pre88's. they can allow some realy bizar oscilations if they are scraged.