Drive train/Tranny/U Joint

What is your question?

When accelerating from a stop there was a slight delay before the drive train would engage the rear end and move the truck forward.A clunking sound could be heard as well. I thought it was a U Joint issue. I put the truck in neutral and spun the drive shaft in my hands and did not feel or observe any play or sloppyness in the U Joints. The shaft would spin approx. 2 inches in either direction. There is now a shuddering when accelerating hard. Also a shuddering when removing my foot from the accelerator at highway speed. Could it still be U Joints? Im hoping the tranny or rearend is not going out. I only use the truck for back and forth to work. Ive never towed anything heavy with the truck. 232k on the odometer. Thanks