Wicked Vibration . . . need some help.

[Ridinghigh]

Got a pain in the *** problem and thought maybe some of you might have had it as well.

 

I have a 66gmc 3/4TON 2wd with a 350 and a Turbo350 tranny. Rear end is a 4.11 posi. Solid drive shaft and the tires seem to be in great shape.

 

Low speeds I have a harmonic vibration. 10-19 mph or so. Then at 20-39 or so its gone but at 39 and above it comes back and gets worse with speed (only speed not RPM). The sound and vibration both worsen equally. I thought it could be U-joints so I replaced those. Thought that the shaft was too far into the tranny but that seems okay (bout 1.5-2 inches out of the tranny). Then one day I noticed the Tranny had become unbolted from its mount and was about 2 inches to the left of where it should be! So I pulled it back over (which was quite hard) and remounted it. Since then the vibration has been worse. It is possible the driveshaft has become bent (it goes through a oval crossmember).

 

I jacked up the rear end and put it in drive and gave it some gas and the vibration was there if i remember right making it less likely to be the tires or suspension.

 

Also, the engine seems to sit like 1.5 inches to the right (looking at the engine) more than the other side however its always kinda been this way. The engine mounts are about 2 years old I wonder if these are bad or not mounted properly or what.

 

If you all have ANY ideas I would greatly appreciate them.

 

Thanks.

 

Dylan

[cgabe]

You said the tranny came loose from the mounts and you shifted it back in place.

How do you know where the right place is for the tranny?

There is a posibility the tranny and the drive shaft dont make a strait line. See if you can eyeball a strait line and then tighten the tranny.

Second, have your drive shaft rebalanced and the shop will also be able to tell you if the shaft is bent. Good luck.