The truck is not mine, but i figure this would be a great place to ask for advice. The truck is not a gmt but shares same electronics like it. it's a v6 silverado. the issue is it will drive perfect for about 20-30mins, then completely lose all gears(feels like its in neutral more so than slipping.) shut the car off for 2-3mins and then it is perfectly fine again for another 20ish mins. My guess is the transmission control unit, but others have said it could be the solenoids. does anyone know the continuity check steps for the chevy solenoids and/or control unit/module?