WHAT IS WRONG!? TRANNY MOUNT OR U-JOINT!?

I've been doing this with my car for about the past 2-3 months! I have a 98 Z28 with no respectable mods but i've been going through drivetrain parts like mad. Rear axle bearing replaced twice in 1 year. Anyways bout 2 months ago i replaced my u-joints. Like an idiot i didn't get my driveshaft balanced until about 1 week ago. Up until the balancing of the driveshaft my car vibrated pretty badly from 55 and up. Well all that went away after balancing. Well low and behold 2 days later a new bad sound arrives!
When starting from a stand still if i punch it a little you can hear a pop pop pop sound and a vibration all the way till around 55 then it smoothes out. But does come back from time to time especially when i get on it again. I just got 4 new tires mounted and balanced so i know it's not them. Could it be my u-joints bad already or did i jack up the tranny mount!? HELP ME!!


