I am getting a drumming sound from what seems to be the center of the car at aruond 21 and 44 mph,seems to be there in all gears{automatic} accel or decel,I have already replaced giubo and made sure center bearing was smooth and rubber support was solid.the u-joints weren't stiff or notchy.Could the driveshaft assy be out of balance?

Did you disassemble the driveshaft when you did the guibo replacement? If so, did you mark the halves before disassembling it, so you could reinstall the shaft in the correct orientation, with the u-joints lined up upon reassembly? You can try to rotate the driveshaft 180 degrees. Also, sometimes the two driveshaft halves can be off by a spline or two because it's hard to gauge if you put it back on the EXACT same spline if the car is 4 inches from your nose! :)

Of course, my post is rather useless if you didn't separate the driveshaft halves!

Hope this helps!

did not split shafts