Driveline Vibration

I just got my 1992 IROC R/T back together with a lot of new parts. I think their may be multiple issue here but I was looking for someone with experience on this. I just rebuilt a new to me A523 with an OBX. Any time I step on the accelerator I can feel a pretty strong vibration, but only when accelerating.

I just installed the Rich Bryant BC Racing Coil over suspension on the front. I think the front is still too low as the lower control arms are pointing up instead of level or down. I have not gotten an alignment yet, so I have no idea how far that is off. I am going to add another 15mm of height in the front and see what that does. I have not had a chance to install the rear set-up yet.

On the motor mount side of things, I already had a Polybushings front and driver mount installed. I added a Polybushings passenger mount. I have a solid bobble strut. After installing the engine with the passenger and drivers mounts, I installed the front mount. I then added about 1/8" of preload to the bobble strut.
I literally took the car for a 15 min shakedown this morning just to see what is going on.
I need to raise the front as said and also get an alignment done soon. I am not sure if this vibration is caused by binding because of the front being too low or this vibration is being transferred because the motor mounts.

I would probably first check the engine positioning after doing the passenger side mount. Did you need to re-adjust after putting it in? Did your passenger side have the two flat spacers?

I had the complete motor and trans out. I did not just swap out the passenger mount. Everything was removed and reset. My passenger side had 2 spacers before and I used those same spacers with the new motor mount.

The polybushings mount eliminates the need for the shims.

If you have a PB front mount, DO NOT preload the bobble strut! All this does is wear the bushings of the bobble out faster and transmit a LOT of vibration to the car. I learned this the hard way...from experience.

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Originally Posted by ajakeski

The polybushings mount eliminates the need for the shims.

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So I can remove the shims then?

Quote:

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Originally Posted by Reaper1

If you have a PB front mount, DO NOT preload the bobble strut! All this does is wear the bushings of the bobble out faster and transmit a LOT of vibration to the car. I learned this the hard way...from experience.

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I will pull the shims out of the passenger mount, then loosen the front mount and bobble strut, then torque the front mount and reset the bobble strut with no pre-load. As it sat before, I had about 1/4 of possible movement at the bobble strut and per suggestion I pre-loaded it with half of the movement available.

Quote:

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Originally Posted by ajakeski

The polybushings mount eliminates the need for the shims.

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Interesting, I didn't know that. Does that go for both the early and late style? I was having difficulty when I tried to install a late one and ended up just putting a stock style in for the time being.

The passenger one that I received from Johnny is a filled one, it is not the solid one. Can I still remove the spacers?

Ask Johnny Spiva

Just make sure the engine is level. Eyeball it or use a level. Dont want the passenger side higher.

My guess is the axles.

Quote:

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Originally Posted by Johnny

Just make sure the engine is level. Eyeball it or use a level. Dont want the passenger side higher.

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Talked on the phone with Johnny today and came home and laid a level across the core support and across the engine. Looks like the passenger side is high, so I’ll be removing the shims.
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I had the same issue with my Saturn. Had to go back to stock ride height. That was the only thing that worked to get rid of the vibration.

Did you center the Engine/trans before tightening the axle nuts??

When centered, the axle stubs in the wheel bearings should have equal in/out spring loaded "play"

Inner CV's can vibrate under acceleration when compressed too tightly.

Thanks
Randy

So here is what I did to eliminate the vibration:
I removed the shims under the passenger side motor mount which lowered the passenger side of the engine and made it almost level.
I removed the 2 rubber washers that I received from Johnny that I installed on the passenger side of the motor mount. They are not needed on my application.
I loosened up the rear bobble strut and reset it with no pre-load after the passenger side and front motor mounts were snugged up.

Glad to hear you got it. That's at least off the list now!

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