dereklm280

Hey everyone. I got myself a 89 944 NA last weekend and have been learning a lot over the last week... foremost that these cars are not as simple and cheap as the Datsuns I used to work on. I plan on doing clutch, brakes and wheel bearings here soon but have noticed something a bit more concerning.

When going over rough road (pot holes, small bumps, repaired road, etc) I get a weird shuddering/shaking in the rear end and it feels as if the back of my car is like a phone vibrating and moving across a table. When going over a speed bump I dont feel anything (both wheels exposed to the bump at the same time) and otherwise the car rides smoothly. Nothing is visually off from underneath, the suspension appears to move freely when bouncing the car in the back, the car tracks pretty well although the steering wheel is off by ~15 deg while driving straight. I gave the CVs, transaxle and whatnot a good jostle to see if anything was loose or if a mount was damaged and it all seems pretty tight (not the same as a driving load of course).

Obviously the car shaking while going over the bumps can just be because its bumpy but this feels different. Just one or two excitations/bumps can cause what feels like 5-6 cycles of this vibration that is over maybe a second or two. I have had it happen under load (going around a corner, accelerating and maybe hitting road imperfections) as well as just cruising over some road patches while keeping a steady speed.

Any thoughts on what this could be or things to check? I'm scouring the forums as well but havent found anything yet.

My list of things to check once I have it inside and up on jack stands are the CVs, motor mounts (I have a tiny bit of vibration at idle, not sure if this can cause the more severe shaking under load) and more generally the suspension and transaxle. A lot of that will be out anyways for the clutch replacement so hopefully I can find something then. I cannot troubleshoot it once its torn apart though so let me know if there is anything I can test in the near future...

Thanks
Derek

Gage

Could it be exhaust related? The factory systems, particularly the 89's with the added resonator, are quite heavy. If the resilient mounts have failed or are not properly installed the system can develop a crack (usually inside the muffler) that can cause it to oscillate.

jeyjey

You could perhaps get a roll of exhaust wrap and wrap the parts most likely to make contact with other things to test out Gage's theory....

harveyf

I agree with the others to check the exhuast. It will give you a buzzing noise if it leans up against the body.