Had a bad vibration on my blower car several years ago. Checked out driveshaft, yokes and even swapped driveshaft (installed alum). Checked out clutch and changed clutch (went from Dual Fric. to Motorsport). Still didn't fix the problem. Bought a SFI balancer and pulled the factory balancer. Found the snout on the stock balancer had a hairline crack. Replaced balancer and problem was resolved. If you have any mods on a Stang I would buy a SFI balancer anyway. Stock balancers a junk in a performance application. After I had this problem several Mustang owners with semi to highly modded cars have had the same problems. The Force
