Starts between 55-60 mph. Vibration and noise increases with speed. As long as I stay under 55 I have no problems. Car has new tires and new U joints. Wheel bearings maybe?

Thanks!

Did the rearend make the same sound or vibration before new tires were installed?

If not, I would suspect tires. Some tires, maybe all, don't know for sure, have tread design that is not symmetrical in respect to circumference. In other words if one were to dissect a tread and lay it out in one long strip the spacing of tread compresses and expands linearly a bit. I think that a tire with or without this changing of the pattern may cause some strange harmonics to set up. Or I could be all wet.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Car had 25 YO tires on it when I bought it. They barely made it to a tire dealer where I had new tires and brakes installed all the way around. So to answer your question, I don't know if it made the noise before. Two of the originals blew out before I could get up to speed. LOL