Hi all,

A friend has a Gen II Hemi-powered 1970 Barracuda, with Keisler 5 speed transmission. This car has been on the road for several years now, with no issues. Yesterday, he ran it through the gears, up to 4000-5000 rpm, and a fairly severe vibration started happening. He hasn't done any driveline work on it recently, nor changed tires/wheels, or anything like that. He crawled underneath to look for anything obvious, found a slightly loose nut on one of the transmission crossmember bolts, and tightened it - with no change. I suggested he check for a missing drive-shaft weight, or wheel weight. Any other ideas on what could cause this to happen? Thanks for any suggestions.

Edit more info: he says it seems to be speed-related, not rpm related. It starts at about 85 mph, 4000 rpm in 3rd gear, gets worse as speed increases.

Roger