High RPM vibration on LT4
 

When I get around 5K RPM at full throttle, I'm getting a bit of a vibration in the drivetrain. My first thought is the flywheel. It's not teeth chattering, but it's quite noticeable. Any thoughts on this would be greatly appreciated.

getting the same thing on my 94 I am going to check the C beam and u joints

Me too. It is like a low rumble when I really get on it. I changed the rear hubs thinking it was the bearings, and also the half shaft u-joints. No change. I should have changed the drive shaft u-joints while I was in there? By any chance is your car a convertible? Please let me know if you figure it out. Sounds like the same problem to me.

Mine is a coupe. I'm going to put it on the lift next week and start tearing into it. I'll let you know what I come up with.

Clutch been changed recently?

Do those use the dampner on the driveshaft like some of the earlier C4s? Its up close to the trans. I think they are bonded on and can come loose, had that issue on my 89

I think its normal, im running a richmont 6 spd and these cars have no rubber trans mount just hard bolted to the rear end, it drove me crazy for a long time, you just pick up more vibration with the setup

Mine is beyond normal, something is wrong.

No mine is not normal either. This is my 2nd 92 6spd and the other didn't do this. I have figured out that it has nothing to do with the car moving. It is just high RPMs. It happens in the driveway when the engine is reved up. Make sure you try this before spending any cash on u-joints and such like I did. I'm thinking motor mounts maybe? Any ideas?

http://forums.corvetteforum.com/c4-t...ight=vibration
Read this for 6 speed cars

Thanks rob. I was just reading this. Going to go check it out. Stand by......

OK. Looks like mine starts at around 3500 to 4000. Does not smooth out above 4000, and does not change or get better with the clutch depressed. So must be in the engine, right?

I think I'll go take the belt off just for the hell of it.

No such luck. Same thing without the belt.

Anybody have any ideas?

The whole clutch assembly spins whether the clutch is pushed in or not, it could even be a pilot bushing for the transmission input shaft. My automatic is doing the same thing though.

Bet it's the balancer. Damn it!

:iagree:
Did you by any chance bang the balancer to get it off at one time or another?

Mine is so smooth thru the whole RPM band

I haven't, and I doubt it has been off before, but you never know? Is there a way to tell other than replacing it?

That's my car now. It still had the vibration when I got it. I changed the clutch and flywheel and it is completely gone. What you are describing is exactly what my car was doing. When I was trying to locate the source of the vibration, I was certain it was coming from in front of/below the dash.

Don't know how many miles on your engine or it's condition, But I had a bad vibration at high RPM and it was the main bearings. It didn't knock or anything but I felt the vibration in the whole car.