View Full Version : Bad vibration, any ideas?

05-14-2003, 03:29 AM
I just got done changing out my Harmonic Balancer, crank pulley, and the associated bolts today on my 89 SC 5-speed with the help of some friends. The reason being was because the car has had a terrible vibration since I bought it about 2 weeks ago. The cars acts exactly the same; I might as well have left the original HB on there seeing as it had no play or visible wobble.

The vibration is relative to RPM, not speed. It exists at idle with the tranmission disengaged, during regular driving, and is really felt when the car is taken above 3000rpm. At idle, the vibration is slower and shakes the whole car. If the hood is popped, you can watch the engine shudder in the engine bay. As you drive the car, the vibration becomes less noticeable between 1000 and 2500rpm, but is still felt vaguely in the shifter. As you take the car above 2500, the vibration gets quicker and more intense, to the point of shaking the chassis and shifter at anywhere over 4500 rpm.

Now, I would think the fact the car runs properly with no misses, etc. rules out any injector/spark issues. This would leave me with no other culprit than possibly engine/tranny mounts, right? Does it sound like that may be the problem here? I would point a finger at something in the driveline, but that wouldn't explain the fact the vibration still exists when the clutch is pressed.

Any help or insight would be much appreciated. :confused:

05-14-2003, 03:37 AM
I think you have eliminated the HB and the front of the car. The only thing left is the driveline. I don't have a clue about flywheels and clutches, but it's probably something there out of balance or improperly centered.


Michael Mattix
05-14-2003, 08:51 AM
Engine mounts, engine mounts, engine mounts! Is your oil filter hard to get off (does it rub the frame when it's almost off)? If yes, engine mounts, engine mounts, engine mounts!

05-14-2003, 10:13 AM
Last year I had an aggravating vibration after having in my AOD rebuilt and couldn't seem to track it down. Eventually it diminished a bit, but I just did my motor mounts a few weeks ago and the driver's side mount was cooked. The vibration - what was left of it - is completely gone now!

05-14-2003, 10:20 AM
Mine was the same till I replaced the engine mounts with new solid rubber units from Parts America (www.partsamerica.com). Or go to www.mn12performance.com as well.

You will be surprised at how smooth it will be after you change them out.

Good luck and have fun!!


05-15-2003, 02:35 AM
Thanks for the advice guys. I'll pickup some mounts and see how much they help. :)

boosted chicken
05-15-2003, 10:25 PM
how bout if you've changed the HB and the motor mounts. pulled codes (none) and checked for vacuum leaks till you went berserk?
my 89 auto shakes at idle but clears up at 1300 rpm and above. i
am out of ideas.:(

05-03-2005, 02:30 AM
Didn't relize this thread was so old!!!!!
Possible plugs and wires? I've seen bad plugs and wires cause this!