Longtime owner of 63 Dart convertible, auto trans. When stopped in drive, like at a stop sign. there's a bad vibration. It seems like it's coming from behind the transmission back through the drivetrain to the rear end. It's been 6 months and is getting worse. Vibration all but disappears while motoring down the road. Motor mounts and engine are fine, replaced an old trans mount but that didn't rectify the vibration one bit. Also, when I turn sharply to the left around a corner there's a loud knocking under the hump between the bucket seats. May or maynot be related. Any ideas on what needs to be repaired or replaced?

Hm... sounds a little odd. The noise when stopped makes me think you might want to check your heat shields and stuff like that. Short of some sort of harmonic vibration, I would blame lose torque converter bolts or internal transmission problems, but I would think that would manifest itself at-speed as well.

thanks for the suggestions.......could it be a driveshaft problem?

I'd think a driveshaft problem would manifest while under way, and not while stopped.

I'd think it has to be something like what's already been mentioned, coming loose and vibrating, maybe against the tranny.

I don't suppose it's impossible that it might be the muffler itself.

I kinda wonder if this is to do with the special engine mount that was made for Convertibles. There're lots of reports of using the standard non-convertible mount with no trouble, but...?

Vibration when stopped and idling plus banging/knocking when turning can mean only one thing: Something is touching the floorpan or a frame member, that shouldn't. Could be the exhaust pipe, the engine or trans.

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Check the torque converter > flexplate bolts, those have a tendency to work loose. Under acceleration you won't hear it until they get loose enough.

Check to see if the tail pipe is banging against the gas tank. Been there done that.

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Have you lowered the front of your car by adjusting the torsion bars recently?

no I haven't....thanks for considering that.

replaced my trans mount for same reasons and it didnt help

later found out the new trans mount i just replaced and come apart and i had to replace it again

maybe or maybe not it helps but thought i would throw it out there

How did you check your motor mounts?

Well I replaced them around a year ago, also did a visual inspection and vibration test. Curious, how do you check 'em?

Does your engine appear to be sitting level? Or slightly lower on the passenger side?