Drive Shaft or Transmission?

[firstq]

At around 30-35 MPH, the shudder comes in and stays there around that and higher speeds - most pronounced around 30-35.

I have done some test to to triage where the problem may be coming from:

1. When the vibration is present, I pushed the car into Neutral - the vibration stayed. [trying to eliminte the transmission]

2. Reving up the engine in the neutral at around 30-35 MPH did not make any difference in vibration. [trying to eliminate motor mounts]

Does this mean it is the drive shaft?

Putting the car in neutral at 35 MPH with vibration effectively removes the transmission from the equation? or is the transmission still engaged because the car is still moving? TC locking up?

Thanks

Note: I probably have asked this question before, and I think the consensus was the Drive Shaft - however; I just wanted to confirm the validity of the test

[Q45tech]

Put it on a frame lift and have someone drive it to speeds in gear, the item should be self evident .

Ideally one would want a chassis dyno with a pit so you could observe the car as it would be on the road [supported by tires not frame] but generally the drooping rear tires don't cause errors in diff, or drive shaft, motor/transmission mount, or transmission diagnosis.

[nisstech]

just went through this on my 92'Q. There are a few good starting places,but i bet it is your drive shaft. If you have a late 93 to 95 you just have to replace the center bearing support. The rubber around the bearing sags and allows the angle to change. The 90-92 had a drive shaft that you can not replace the bearing. I just got a 6-95 shaft for 100.00 a local salvage yard,replace the bearing and no more 30 to 35 vib! but still had a 0-20mph vib. this was the tenshion rods, the bushing were not leaking Just very small dry rot crackes and very hard. changed the two rod and no more vib at any speed!

[firstq]

nistech: No local yards here having any Q drive shafts.

You are atleast confirming that 95-96 shaft would fit fine on a 92Q - I had heard it before but this will confirm it.

Now only if I can find a working used drive shaft. My T rods are new.

Thanks

[PalmerWMD]

Yes the later drive shafts fit on the earlier cars.

The dealer only installs the later drive shaft now regardless of wether its a 90-93 or a 94-96.

The only replacement shaft u can get now for both 90/93 and 94/96 is the part # for the 94-96 , 100% compatible.

Fred...

[nisstech]

forgot to also let you know, if or when you find one ask for the brackets for the center mount as thay are differant then the 92'

[firstq]

nisstech: The brackets need to come off the salvaged car as well? So the seller should ship the drive shaft + brackets from the salvaged car?

Thanks

[nisstech]

That's correct. The newer driveshaft the center bearing is of a differant style (larger) the old set will not work. There is a upper and lower brackett. You can get from dealer also for approx. $30.00 or so x 2.

[Q45tech]

Sitting on a wrecked car in a junk yard exposes the rubber to ozone/oxygen just like in use on your car. The 94 are getting near 10 years old............we have had poor luck with used shafts.

The new shaft requires a series of test measurements to insure correct orientation to minimize vibration......see your service manual.

[AZhitman]

I agree with Dennis - I'd call Joe and see how cheaply he can get you one for.

I'd be glad to help you swap it out to save some $$$.

[firstq]

Hitman, thanks for the offer. If you help me take it out, I know places where they claim to fix the U joints and precision balance the shaft - worth the gamble in my view.

I heard though the exahust has to be lowered to get the shaft out - also w/o a lift, fairly difficult DIY, right?

Thanks

[AZhitman]

Hmmm - I haven't looked that close.

Although, for what it costs to have the pipes welded, I'd be tempted to just hacksaw the damn thing off and have it re-welded ($10-20).