I have a 1990 Silverado. I had just bought it as a work truck and a fixer upper and after driving 80% home (40 miles)the transmission seemed to just drop out. No clunks, knocks, slips, etc. Cut the truck off and back on it pulls for a few seconds then gone again. The guy I got it from said he put another transmission in it because the orginal one was shot. The truck will pull itself but only on level ground. On a Bill it just rolls backwards. All fluids look, smell, and feel good. Transmission fluid looks new and is at the correct level. Check engine light came on about 15 miles before it started acting up. Only code in it is from memory and is 32 or eye valve which he said he fixed as it didn't want to idle. Idles great. Has the 5.7L V8. Any idea?