351mustang

I just bought a Mustang from a friend a few months ago and finally got it tuned up it took it down to the track and when I get up to 60-70 mph car shakes real bad!! And I have to let of the throttle..I have skinnies on the front and slicks on the back is this be a tire balancin issue or could or un balanced driveshaft?

dawson1112

It could be unbalanced tires but not likely. It more than likely a bent driveshaft or bad universal joints. The front universal on my 94 was partially stuck on one side and shortend the range of movement that pushed up on the tail of the trans every half revolution . This caused a bad vibration and shaking at around the same speeds your describing.

351mustang

Mines an 88 and I'll def take a look at the driveshaft an u joints an see what's up

dawson1112

When my 94 was doin that I got under and tried to wiggle the drive shaft to see if the uv joints were shot but there was no play at all in them . The only way I noticed the problem was to jack the entire rear of the car off the ground and spin the drive shaft . when I did that I noticed the tail stock of the trans was moving up and down every 180 degree rotation. it was a very slight movement maybe 1/8 of an inch but it was enough for me to pull the drive shaft to discover the front uv was partially siezed up on one axis. Im sure it was exadurated upon higher speed.

Tony71502

Check your front ball joints first. That is usually the problem.

caaraa

Hmmmm ... I'm going to have to think about that one

jsepulveda

If you still havent solved this, check the bolts at the rear end where the u joint bolt to diff. When I got my car had similar issue with vibration and found that my bolts had backed out a half inch.

lxman1

Mine had a bent driveshaft. Perfect time to add the Ford Racing aluminum shaft like I did.

351mustang

I know it's been a while but I figured out what was wrong a while ago..turned out it was a bad tire..the mt drag slick had a grove in the sidewall which made it vibrate hard..switch tires an it went away

mjr46

glad to hear the update