[FWDLK] I'm picking up bad vibrations

[Dan Morton <morton@xxxxxxxxxxxxx>]

Apologies to the Beach Boys...  I have a curious gremlin that only appears
at about 30 mph, and then only when there is no load on the drive train --
I'm not accelerating nor decelerating.  At this speed (and yes, I'm in 3rd
gear with a manual transmission), if I'm not climbing a hill and press just
slightly on the gas to maintain my speed, I get a lot of vibrational noise
under the car.  I can't place it, but it doesn't seem to be localized to the
front of the car or the back.  If I step on the gas, the noise goes away.

Now I just had the rear rebuilt, and the transmission was pulled at the same
time -- no signs of wear there.  However, I had replaced one of the
universals, but not the housing for it.  Could this be my culprit?  Again,
it only appears in 3rd gear, but I'm not really moving all that fast when I
need to shift out of second.  Does anyone have suggestions for how I can
tell if my driveshaft is the problem?

        Dan, TWSAM
        '55 Savoy