If your "VERY" carefull, you can put the truck on a lift or jack stands,(under/supporting rear end). Run in low gear, look/listen,(stethiscope), for noise and run-out of drive shaft etc. Good Luck, ateam.:cheers:
I go thru this with EVERY new mechanic i do business with that makes the same mistake......
When you check the shaft in the car there are angles that the company who built the car put in the driveline...
When the shaft starts going the joints start oscillating and the shaft looks like its running out.... as rpm at the shaft increase this will increase, its why when you build for performance you REMOVE angle at the motor and trans, shaft and diff., after a certain amount of rpm you can not have any angle or you will have a vibe. .
this is a normal issue as when the cross goes thru the next phase it will move the shaft forward and back somewhat and it will appear it is bent... or running out, and as i told HUNDREDS and hundreds of mechanics making this mistake, i can take your customers money now and build them something they do not need when they may only need balancing...
This is why you can't have the yokes out of phase, or if you do you'll get a wicked vibe.
Do not use the car for a precision piece of equipment to check a shafts run out... it doesn't work, and especially not at any powered speed.