I get a light vibration at rpms in excess of 4k, It has been doing this for about a year now so I'm starting to wonder if it is the tranny, wouldn't it of died by now?
I have a SPEC 3 clutch w/SPEC steel flywheel, which besides occasionally giving me fits on getting the car into a gear from neutral it works fine.

 

i had vibrations like that once..it was the u-joint. it got worse as rpms increased and lightened up again when it shifted..i didnt think thats what it was at first but it fixed it

 

I thought that could be it...but last week I replaced the rear with a dana 60, the driveshaft yoke and u joint with a chorme molly monster, and a UMI torque arm.

 

hmm..other than the u joint i dont have any ideas sorry

 

It is only high RPM, so I would guess it has to be from the input shaft up?

 

Update: This also seems to happen with or with out the clutch engaged, I can rev it in neutral and the car will still shake. So this limits it down to motor mounts, tranny mounts or input shaft...right?

 

ttt

 

My car was doing this and it happened to be the clutch assembly wasn't balanced closely enough (zero balanced; my motor is internally balanced). I could have lived with mine, but it bothered me knowing it was vibrating like that. I didn't want to shake the bearings loose in the lower end (that I just paid a **** ton to have built). Did the vibration start after you installed the clutch assembly? Do you have a poly transmission mount?

 

Rubber tranny mount. It has been a long time sense the clutch install...but I'm almost certain it was there before the clutch install.

Could the harmonic balancer cause this problem? I have a cheap autozone replacement.

 

Well, it shouldn't be the balancer (supposed to be zero balanced from the factory), but it is an Autozone cheapy. To test this, pull the pulley off, start the car, and rev to 4k+. It won't hurt anything to run it for a minute w/out the belt or pulley.

 

I'll tryt hat, anything else I can do at the sametime to try and track this down?

 

Unfortunately, I don't think so. I just went through the same thing and the next step would be pulling the tranny out. If it does it with the clutch in, it's either the balancer or the clutch assembly (unless it's internal, which would be bad).

 

I have a bad feeling it's the input shaft. It seemed a little on the loose side when the tranny was out last.

 

Well, if you can sit in the drive way, with the clutch pressed in, and it vibrates, it shouldn't be in the tranny (input shaft). When the clutch is in, nothing in the tranny is turning.

 

I was under the impression the input shaft always turned.