Nasty94Z28

I have a 1994 Z28 with a Bad Vibration if you in 3rd gear and your going 45-50 feels like the car is falling apart and when you shift it in over drive it goes away till you hit about 60-65 mph and it starts back. any info will Help.
Thanks.

Nasty94Z28

I tryed the tourqe converter bolts and they where tight I checked the Motor mounts they where tight.I checked I trans mount and it was loose and I tightin it and I rasied the rear up and the drive shaft looked like it had a wipple in it.

I drove the After I did this and the vibration is still there but not as bad. I put in nutuel where it was vibrating and the vibrating went away.

hot_red_z28

I hate to say it, but it sounds to me like it could be something in the transmission...

the fact that it goes away in neutral almost completely rules out the driveshaft because it continually spins regardless, and the fact that switching gears affects the speed at which this occurs also makes me think it is not the driveshaft... the problem seems more rpm related than speed related...

now, the TC also spins all the time, regardless of neutral or not, but the internal parts aren't really rotated while in neutral... however, it would probably vibrate at all rpms if it was something broke in the converter...

the only other possibilities I can think of (and the ones I would check for first) is possibly an engine miss or exhaust pipes vibrating on the underbody at those given rpms... I suppose it is also possible that the flexplate is out of balance, but if it is the original that is probably unlikely...

-Garrett

Nasty94Z28

I know it vibrates in park sometime put not all the in 1500 to2000RPMs sometimes. I now if you reve it pass that spot it goes away and before it it dont do it eaither.

You can have it in drive and keep in drive and go passed where it vibrates It stops to.

hot_red_z28

if it does it in part sometimes, I'm going to say check your headers/exhaust to make sure nothing is vibrating on the underbody...

after my header install I had to massage things around under there to keep from having the same **** happen... it would vibrate at certain rpms but not at others...

by looking you prolly won't see contact... try shaking on the pipes and stuff to see if you notice it hitting anywhere when it is being shaken...

Nasty94Z28

Ive already checked that just around where the cat is but no where elese. where elese would you check at.and did it do it in park to.

hot_red_z28

mine was hitting on the firewall edge and on that tunnel brace thing that the exhaust goes over...

Nasty94Z28

How far does the header spossed to be from the stering arm mine is so close it looks like its hitting it.

Umbrae

Check your u-joints and driveshaft.....

hot_red_z28

that's a definate possibility... most times there isn't very much clearance... make sure while the car is sitting there that you can turn the wheel both ways...

even if you can, if it is close enough, maybe within 1/4" it could very well be rocking over there under certain rpms and bumping the steering arm some...

at certain rpms sometimes the engine will vibrate more than at others during normal operation... the vibration may be just right at those certain rpms to make it wiggle enough to get the headers to touch...

if it is more than 1/4" away while not running and you can rock the motor over so that it hits, that may be a sign of slightly worn out motor mount(s)...

-Garrett