vibration problem

I'm going to join in on this. I have a long history of vibrations in Darts and have never been able to locate the problem. I have a '69 Dart and it HAD a 318, 904 and 7.25 rear. It would always vibrate above 60-65mph. The 7.25 was modified from small bolt pattern to large bolt pattern by the previous owner and I know he did a backyard job with a hand drill on it and always figured that that was the problem.

My girlfriend at the time was impressed by my Dart and also bought one. It is a completely stock and original '69 with a 273, 904 and 7.25 rear. Hers also vibrated like mine. I pulled the motor for a rebuild and also rebuilt the transmission. The 904 was fitted with all new bushing etc. Because of the vibration I also replaced the driveshaft with another one that I had lying around. To our disappointment the vibration was still there.

I recently completed a build on my Dart and it now sports a twin turbo 318, 727 and (don't heckle me) a 10 bolt chevy rearend with a 3.73 gear hung in a self-fabbed 4-link. Because of the different trans and completely different rearend I also put in another driveshaft. I would have expected the vibration to be gone, but much to my disappointment, it's still there! Oh, I also fitted brand new steel wheels (Cragar Deluxe 69) with brand new tires. When I put her in neutral and rev the motor to any rpm, it doesn't vibrate. It's only when I drive.

By the way, a friend owned a '69 Dart with a 360, 727 and 8.25 and his did exactly the same.

What's with these A-body Mopars? Did Ma Mopar incorporate a natural speed limiter into these things to stop you from driving them past 65mph?:banghead: