So I have a 1999 Sierra 5.3, I had the transmission rebuilt in October. Last week I was driving and lost all gears, no slipping, just like the truck was in neutral. I get the truck towed home, all of a sudden I have a transmission again. I am able to drive about 2 miles and I loose everything again, shut the truck off, restart a few minutes later and the transmission shifts fine again and then the cycle starts over. Anyone have any ideas on what the problem may be?