If you suspect the trans, check the obvious first. Full fluid level , fluid color (should be red). When was it last changed? If its old, maybe just changing it & cleaning the screen in the pan will fix the issue.

 

change the trans fluid filter

 

Grease the slip joint on the front of the driveshaft.

 

Its just a screen which can be cleaned. If you happen to have one of the felt type filters, then replace it.

 

No no no, that doesn't necessarily mean the u-joints are good. U-joints are cheap, replace them, I guarantee that's your problem. You are opening up an unnecessary can of worms with the transmission.