Rear end Vibration?

[1990StangGT]

Just bought a 93 ssp fox. While driving it home I noticed 1st to 2nd gear has a pretty bad grind issue. Almost certain it is a snycro. The biggest issue is between 60-70+ mph. The rear end has a horrid vibration, when I put my foot into the gas the vibration is there but isn't as bad. When I let off of the gas the vibration is horrible until I get back below 60. I also noticed the rear end was leaking fluid once I got it home.

It has 3.55's with 5lug ranger axles in the rear. Another thing to note is it gets even worse when running through all the gears at WOT and shifts from 3rd to 4th at WOT at speeds above 60mph. I plan on pulling the trans this week, could it be casuing the issue or is the rear end shot?

 

[jrichker]

Check the driveshaft to make sure it hasn't slung off the balance weights. They are normally tack welded on. Also check to see that the paint mark on the driveshaft lines up with the paint mark on the rear axle flange.

Look to see that the cast iron "dog bone" is still on the rear axle and that the rubber mounts are in good shape. The "dog bone" is a large cast iron piece that mounts on the lower part of the differential housing just aft of the driveshaft mounting flange. Its purpose was to act as a vibration dampener and reduce driveline vibrations.

 

[1990StangGT]

I'll be sure to check those. I've also noticed the leak is coming from the rear diff cover not being sealed properly. Also where the trans and driveshaft meet there is a small leak. My questions is why is it so noticeable at high speeds but not so much at town driving?

 

[90stang5speed]

I had a vibration issue like that. for me it turned out to be loose bolts holding the drive shaft to the diff. I took them out, put some blue lock tight on them and problem solved.

 

[2000xp8]

Buy an aluminum driveshaft.

It's worse at higher speed because the driveshaft back parts always spin as fast as the car is going.

That's the tell tale sign that the problem is behind the trans, not in front of it, if it were in front it would be an rpm based problem, not speed based.

 

[jrichker]

The out of balance condition is most noticeable at higher speeds. The faster things turn, the more critical the balance is. Some out of balance conditions are most noticeable at multiples of the primary out of balance speed.

 

[Stroked N Blown]

Same thing happened to me. Bought a 89 GT. Drove it over 65 mph and it vibrated uncontrolable. Bought an aluminum drive shaft, problem solved. get a driveshaft!