i know its hard to "e-diagnose" but this is a really damn weird problem.

my transmission makes a high pitched whirring noise like it has bad bearings, and at higher speeds (80+) there is a vibration like i have a flat spot on one of my wheels.. so i replaced the transmission with another used unit (along with new clutch kit and pilot+release bearing) and it does the exact same thing. is this just a common problem or could it be something else like the engine? it ONLY occurs when the transmission is in motion, completely goes away when i push the clutch in while the car is not moving. noise continues when the car is moving, even when the clutch is depressed and it is much much less in 4th gear, and quite a bit less when im going between 120 and 130km/hour. (its not a wheel or brake issue, wheels and tires are brand new and the brakes do not drag at all. one is slightly warped but it doesn't touch so this would have nothing to do with it)

one really weird thing is that if im going at highway speed and downshift into forth to slow down, the entire car will start to vibrate pretty bad UNLESS i have the engine revved up a little too high to match the speed of the transmission and kind of let the transmission "pull" the engine down to the correct speed, then there is no vibration at all (this confuses the hell out of me)

when im moving at 80kph or more and push the clutch in, the car makes kind of an intermittant vibration (it pulses on and off) seemingly dependent on engine RPM, yet when the car is not moving it doesnt do this.
the engine does vibrate a tiny bit at high rpm like 5000+ when the car is not moving, clutch engaged or not. but im assuming this is normal?


props to anyone that read that whole thing and i appreciate any ideas you might have before i decide to just throw another transmission and a diff at the problem and hope it goes away.

 

i have the same problem on my 86 na. its whines in 1,2,3 and barely in 5. i just replaced the tranny oil and its a little better but always whines. and i had a vibration at over 80 and at certain speeds. turned out my driveshaft bolts were lose allowing it to move either way. and your car possibly vibrating can be your transmission mounts. mine need replaced because i can hear it clunk once in a while when i shift.

 

also tell us more about your car what year and all that.

 

its also an 86 NA, base model.

i just got a new rear end and the mounts are fine so once i put that in if i still get the vibration its gotta be the driveshaft or tranny.

and yeah sometimes when i shift it clunks but only when i actually shift not when i actually engage the clutch, just when i shift..which is weird

 

same here not my clutch but my tranny hitting something when i put alot ofpower to it. lift it up and check your driveshaft and see if itmoves inside the tranny when in Nuetrel and see if it clunks. then u will no its your mounts.

 

Perhaps the pilot bearing is missing from the rear of the eccentric shaft? If it is, the transmission input shaft won't center itself in the e-shaft and will run crooked.

It is hard to say though. Check the transmission mount for play as they are almost all worn at this point. Check the engine mounts (especially passenger side).

Check the front diff mount, they often break.

Check the driveshaft for any looseness, as well as the CV axels.

 

i sure hope the pilot bearing isnt missing as the mechanic charged me probably 2 hours labor just to remove the damn thing! haha

and yeah my engine mounts are probably bad, ive been considering putting in one of those "torque brace" things to help with that. the transmission mounts are alright but the diff mount may very well be bad. will find out once i install the new rear end.

i will check the driveshaft but im not really sure how to check the cv joints i'll probably get the mechanic to do that when he does the transmission swap. still not sure if i want to install this other transmission i got because of the axial play in the input shaft. may be a bit too much.