James Rader

I'm not detecting any play in the rear differential. All the play is at the slip yoke at the tail cone of the tranny. Am I missing something?

1999 C2500 2wheel drive Truck started to clunk not long ago when putting truck in reverse then to drive or drive to reverse and sometimes park or neutral to reverse or drive. Now it has also began to get a heavy driveline vibration especially at highway speeds mostly when I let out of the gas and coast. So long as I'm accelerating or decelerating it doesn't seem to vibrate most of the time unless going between acceleration and deceleration it might vibrate momentarily. I have carefully inspected all U joints and carrier bearing and they seem solid with zero play. With truck in neutral and turning drive shaft back and forth there seems no abnormal slack in the rear end and no deflection up or down of driveshaft. However, I can push my slip yoke at the transmission tail cone up and down with nearly a half inch deflection. I'm not an automatic transmission mechanic (engines, suspension anything but auto transmissions). I believe the problem is with the yoke and possibly the tail cone bushing? Before I order brushing, rear seal, and orings and tear into this, is there anything that I need to look for other damage points or concerns I should address? Tailshaft wear? yoke wear? Other internal or external? My greatest concern is wear internally that may need addressed.... thank you in advance for your knowledge and willingness to help...