Source of bad vibration? (Need suggestions ASAP!)

[J Banning]

I've got a really bad vibration that seems to be coming from the rear end of the car. I can feel it slightly under normal driving conditions, but it’s definitely the worst at the end of the track when I'm decelerating from WOT in Drive. It shakes violently... like a wheel is coming off. I feel it in the floor, the steering wheel, and even the swingouts in the rollbar will rattle!

- I’ve checked all the wheels & bearings for play (none).
- I’ve checked the torque on all the lug nuts (none).
- I’ve gone under the car with a pry bar to see if there’s any play/cracks in any of the control arm mounts (none).
- I ended up swapping the trans mount with another used one (no change).
- I've also torn off all the wheel weights on my slicks (no change).
- I’ve even replaced the swaybar bolts with new Grade 8 fasteners.
- I have a HRPartsnStuff trans mount coming too.


Friday night I will:
- Re-check tightness of: engine mounts, bellhousing bolts, crossmember bolts, and convertor bolts.
- Swap in another driveshaft.
- Install the new trans mount.

Any thoughts? I plan on attending the EFI Shootout at E-Town THIS SATURDAY.

Thanks,
-Banning.

 

[1970gsx]

Check the driveshaft. Could be bent or have bad u-joints. Put the back of the car up on jackstands, start it up , put it in drive, and observe the shaft as it spins at idle. Anything other than dead straight you've found your vibration. Also check the tires and rims while your at it.

 

[J Banning]

Will do.

The driveshaft, tires, and wheels are the same ones I ran last season. none of the weights have been knocked off of the driveshaft, but I'll recheck them all any way.

Any other ideas?

Thanks,
-Banning.

 

[blackbuick87]

I didnt see where you checked the rear gears, unless you did it when you did the rear bearings.

 

[REDS HOT AIR]

i'd say driveshaft too..

a weight dont have to be missing...the stock driveshafts are not that hard to get some slight twist in which will make them vibrate.

mine was vibrating too then i put in a alum. shaft and it cleared up.

 

[Joe 1320]

I'd have to vote Driveshaft or the rear yoke may be going south too. It may be in line under engine load, but get when coasting down after a shut off it lets the driveshaft get ever so slightly out of line.