[SOLVED] Vibration at 2500rpm when decelerating
 

SOLUTION DOWN THE THREAD

I just swapped out my stock clutch for an ACT SB7-HDSS (lightweight 11.8lb flywheel) this weekend. Now I'm experiencing noticeable engine/transmission vibration from 2200-2700rpm with the bulk of the noise/vibration at 2500 rpm. This is only apparent during deceleration.

Is this expected with a light flywheel, or do I maybe have a different issue?

Everything lined up correctly when we mated the transmission to the engine, and all of the usual clutch swap parts were changed (fasteners, throw out bearing, fork, etc.)

Hey, Andy2002a, you can zap one of your thread starts - ya only need one - ;)

You may wish to review how you bolted (orientated) the flywheel to the crankshaft and how you orientated the pressure plate to the flywheel.


humfrz

We did the standard criss cross pattern that the service manual shows. So it would have been hard for us to have skipped one, but I will keep that in mind.

What do you mean by the pressure plate orientation to the flywheel? From what I saw there were 3 possible correct ways to mate them (3 guide pins equidistant from each other).

Well, OK. Sounds like you got them installed proper.

Maybe someone that has a light flywheel will chime in with some insight.


humfrz

Mine does it also. Lightweight flywheel, carbon clutch, unsprung hub and cd009. My Samurai also does it with a lightweight flywheel and unsprung disc. So maybe its the flywheel causing your vibration.

Look to see if transmission or exhaust is hitting the body when you let off and the engine twist.

The exhaust hitting the body is probably unlikely since it's the stock one, but I will make sure to take a look next time I'm under the car.

So I took the whole thing apart this weekend and put it back together making sure that everything was torqued down correctly. However, while in there I removed the whiteline insert that I installed.

After driving the car around for a while the noise and vibration has significantly been reduced to the point where it is not annoying. I installed the insert before the clutch so the NVH is definitely from the clutch but the bushing makes even worse.

Thanks for updating us.

Changing from a stock clutch to any aftermarket clutch makes the driveline vibrations considerably more annoying. I had to go to aftermarket to hold the power when I moved to an Edelbrock kit. Started with an ACT. Unbelievably annoying. Switched out to a stage 1 from Exedy. Better, but still harmonic vibrations when lightly accelerating or decelerating. The stock clutch disc has a 'wide angle damper' to help absorb a lot of engine harmonics; the drivetrain is pretty light in the 86 so there isn't a lot of mass to damp it down.

I'm going to try the group n engine and trans mounts next. Still rubber, so better than poly and some report the combination makes things better.

Hey guys I was able to find a solution to this issue!


I decided to upgrade my midpipe to an aftermarket resonated one just for an improvement in sound. However, on the first drive I noticed that my engine vibrations had disappeared! It looks like the exhaust was rubbing somewhere along the front path. I didn’t really consider this before because it had never made any noise pre-clutch swap, and all the bolts were correctly tightened down.

My cheap eBay midpipe really pulled through!