Ok I am new to the 4th gen, just picked up a 93 Z28 w/700r4 to play with. It has a good list of goodies and runs great. Problem is a severe vibration at anything over 75 and gets worse. A little history from the PO, it has Global West Trailing Arms (non adjustable), with anti squat kit (welded), Edelbrock pan hard bar (non-adjustable), Edelbrock torque arm (non-adjustable), Ebach springs w/1" drop, Edelbrock IAS shocks, LG motorsport sway bar. I put it up on the rack to look it over and check pinion angle, ujoints, etc. U-joints look new, feel good, but I plan on replacing anyway. Pinion angle is 0, and I see no way to change it with the parts installed on this car. Also looks like the pan hard bar pulled everything to the right. Is there another way to adjust angle or do I need adjustable trailing arms, torque arm and pan hard bar? I put up a couple of pics in my gallery. Thanks in advance for your help.

 

Is it in the front or back of the car? Wheels dented? Belt in the tire broken? Wheel bearing? Driveshaft bent/missing a weight?

 

Let me add, new tires (good ones), SS wheels all balanced out perfect, not a bearing noise, it is harmonic, seems to go away if I put it nuetral at speed, cant make it happen just by reving motor. My first thought is the trans, I can run it to redline in 3rd and doesnt seem to be as bad, but pop in od and it will take out your wisdom teeth. But after I saw the pinion angle which I thought would be an easy adjustment, I thought I would get that correct first. The PO mainly did strip and stoplight racing, my plan is some open road racing so I need the speed not so much the quickness. It does have 373s that I may change out to 355s.

 

The 93s came with a steel drive(propeller) shaft... And some had issues with vibrations above 60MPH...

On my 93Z, I switch to an aluminum shaft from LPE... But some use just a 98-02 camaro/f-bird aluminum shaft...

 

Finally got a little more time to search for my vibration, jacked up the car, ran it through the gears, has a vib at 2200 in all gears, worse in OD. Pulled the D/S off, same results. Now I am thinking tranny/torque convertor. Any input???

 

Maybe a bad transmission mount.
Check to see if the tranny can be moved. Check condition of mount.

I dont know if this would give you those vibrations but it's worth a check.
Maybe a bad crank pulley?
Can you spin the outter part of the pulley from the inner part?

GL finding the issue.

 

id check pulley system starting with pulling the belt to see if it goes away, if it doesn't Id then check the dampener pulley, if it does you narrowed it down allot.

 

and by your last post, I actually think it might be the TC, you said OD was really bad? could be a TC disag(torque converter disagree w/TCC or locking up early) or a bad TCC(torque converter control)

 

You wouldn't happen to be running a poly trans mount, would you? While it isn't the cause of your issue, it will make any driveline vibrations much more apparent. Found that out the hard way when I added a poly mount to a car with an unbalanced driveshaft- drove fine with the stocker, but anything over 70 with the poly would rattle the car to pieces. Anyway, you might check the converter-to- flexplate bolts just for the hell of it.