1989 SHO Help Needed

[89Rustysho]

I purchased a one owner 1989 SHO in October of 2016, and have since replaced most of the suspension components, brakes and hardware, removed the rear brake bias valve, replaced the front and rear hubs and wheel bearings, cv axles, and most recently the clutch and complete exhaust system. It has now developed a strange phonomenon where the entire engine and transmission asembly shake forward and backward when reversing. This is accompanied by a rattle within the transmission that is paired to engine rpm. The clutch installed was the SPEC Stage 2 Clutch Kit provided by SHO Source, and the new exhaust system is identical to the orginal in design. Any insight on what may be happening is much appreciated. Thank you!!

 

[luigisho]

Could be the clutch. Have you checked the engine mounts and tranny mount?

Also a non biased rear brake can get tricky especially with 89. I think they did not come with anti-lock brakes. At the right speed and hard braking the back end can come around on you.

 

[Irish Pride]

Is the engine genuinely shaking when backing up or are you getting a vibration in the drive system?

The engine actually shaking I would look at bad mounts first. A bad vibration/cavitation when backing up would be the clutch/pressure plate/flywheel. I had a Spec stage 2 once and it didn't last long at all. I went back to stock clutches after that.

 

[rubydist]

I have had this symptom for a couple reasons:

1. The new clutch was "grabby" - this for some reason shows up way worse in reverse than forward.

2. The clutch cable bushing at the transmission end was sloppy and allowed the cable to rock in the locator. (This is the bushing that holds the outside housing of the clutch cable at the transmission end.) In one case the entire problem went away when I replaced that bushing.

 

[BaySHO Performance]

Doers sound like motor mounts. Parking brake *******, hood open, start the engine, engage first, increase the revs somewhat and start lifting your foot off the clutch until it starts to engage. The front of the engine will normally go up a little. If the movement is excessive and it goes down with a thump, front motor mount shot. Doing the same in reverse will check the rear mount.