Ever since Ive had the car,(25000 miles worth). Ive noticed a "HEAVY" vibration at around 3200-3400 RPMs,no matter what gear Im in.The shifter buzzes like crazy and the car sounds like something is "grinding"(that may not be the right word). The vibration smooths out when I power through to higher RPm's or decel to lower Rpm's). Im not sure whats causing this?? Possibly.. Flywheel?.. Something with the Muncie?..Drive shaft or halfshaft?..Rear diff?? wheel bearing??..Yikes..:s .Ive recreated the vibration to try and pinpoint the cause, but I have no idea whats making it?? Anybody have any thoughts about where to begin getting this diagnosed and fixed??