Car Shakes at 65-70 mph?

[Fuch§tang50]

When Im driving on the highway and I get up to about 65-70 mph and the car begins to shake, then I let off the gas and it stops then I get back on it and begins to shake again. I have taken my car in to les schwab and have had my wheels rebalanced and that didnt solve anything. So I am turning to you guys that may know what the problem is.

IF any of this info helps:

its a 79' mustang with 87 internals (302) drivetrain
rebuilt AOD tranmission
17" wheels with 275's all around.

if any more info is needed ill be more that happy to give it.

Thanks,

John

 

[85_SS_302_Coupe]

Do you have an aftermarket gear in the rear end? How's your drive shaft? I'm willing to bet that the drive shaft is the stocker from the original 4 cylinder drivetrain? If so, then it's balanced for a 4 banger and that's your problem.

BTW i checked out your CD page...nice!

 

[86bluecobra]

where do you feel the shake? Is it in the steering wheel or the seat of your pants.

 

[Strype]

warped rim....?

 

[86bluecobra]

warped rim....?

this is what i was thinking or a broken belt in a rear tire.

 

[Fuch§tang50]

Well everything is out of the 87, I put the entire drive train out of it into my 79 so all of it is V-8 related i guess you could say. The tires are brand new, as for one of the wheels i found out that it is slightly bent but was told it wouldnt make any difference. But the steering wheel is mainly where i feel the shaking for the most part, and some in the seat.

 

[85_SS_302_Coupe]

Well everything is out of the 87, I put the entire drive train out of it into my 79 so all of it is V-8 related i guess you could say. The tires are brand new, as for one of the wheels i found out that it is slightly bent but was told it wouldnt make any difference. But the steering wheel is mainly where i feel the shaking for the most part, and some in the seat.

My buddy just sold an '86 that had this exact problem. We changed drive shafts and even the trany and rear end trying to solve the problem and never found out. It was a 4 cylinder conversion too, so maybe there's something that nobody has found out yet. Most people just buy aluminum drive shafts because they seem to eliminate or at least reduce the vibration to a tolerable point. My car had it a little when i first got it, then i got the alum. shaft and now it's smooth as butter.