LT4 LT4 vibration ?

[sinestr]

What would cause my 96 CE/LT4 to have vibration at around 3000 to 4500 rpm? I have checked all pulleys and all are running true. Any thoughts would help.

 

[Shriker]

A vibe like that can be any one of many things.....is it only rpm sensative? Does it vibe when car is moving and stationary or just moving? Does the clutch or A/C being engaged affect it?

I know when I replaced my A/C compressor and a bolt on one of the brackets was loose that really made a difference....check them all. Sometimes rubber engine mounts can be the culprit , take a look at them to see if they are dry , cracked or in need of replacement. Check all of the accessories to be sure they are mounted tightly and working properly (alternator, water pump etc.). You said you checked the pullies and belt.....

It could be a driveline vibe as well. When I got my LT4 I had a strange vibe that seemed to come from the rear. After going through EVERYTHING (bushings, rear diff, rear wheel bearings, u joints etc.) I finally had the driveshaft rebalanced and it did the trick. Also the half shafts could do the same......

Hope some of these possibilities could help you get to the bottom of things.....