Im a little baffled- the 700R4 in my 83 diesel burb just went kaput on the highway. It was driving fine- then I hit a bit of traffic and slowed down. Then I accelerated again when it cleared up. It felt as it if was in third at the time. Then all of a sudden, it lets go, like the truck is in neutral. I pulled the truck off the highway- fluids are not burnt, and was not low. added a fresh quart just to make sure. Still no good. I limp it home in second gear. Still no third or OD. Any ideas, or is my tranny toast?