Had my transmission rebuilt 2 1/2 years ago about 30k miles later. The other day my truck is driving fine and boom wont go. I got it towed to my local garage and the next morning the mechanic says its driving fine. Later the same issue happens. He drops the transmission pan fluid looks good, replaces both solenoid,fluid, no shavings in the filter. Runs for 20 min and then same thing wont go. Any ideas?

 

Is it a 4WD? Maybe your transfer case is going into neutral.

 

Very possible you have a torque converter failing. Did you have the filter changed? Also as @Tom A mentioned if 4x4 try it in 4low when it quits moving. Good luck.
Brad