Ok. I own a 1991 C1500 with the 5.7 engine. Its the automatic transmission, although I am not sure which one it is. Its the stock transmission. The truck has 122,000 miles on it. I had the transmission fluid and filter changed about 2 years ago at 105,000 miles. Other than a slight shutter at 30-40mph when I hit the gas I have never had any ongoing drivetrain issues. I had my truck bed fully loaded with my belongings Moving about 1200 miles. About 15 miles away from my final destination, I smell burning oil, and I look behind me to a cloud of white smoke. I pull over and raise the hood. White smoke everywhere. There is engine oil pooled up near the valve cover on the right side of the engine. Although I thought it was a little odd all that smoke came from what looked like leaked valve cover gasket oil, I ended up getting it towed, just in case. When I get to the house, I start it, and the engine turns over and runs great like always. I put it in reverse. Doesn't move. Forward. Doesn't move. I start looking under the truck. oil EVERYWHERE. check the transmission dipstick. looks pretty much empty and smells burnt. I have yet to find where the transmission oil came from to begin with. The engine oil on pooled on top by the valve covers is still a mystery. Any ideas? I am pretty sure my transmission is shot, but I would like to hear other opinions or other things to check before I give up and go out and start looking for a transmission.