This is on a 92 w250. When I accelerate rapidly the speedometer goes to 50 and then drops off and the trans won't shift till I ease back on the accelerator. The previous owner has put a small bolt in the gap that should be in the TV cable and has replaced the o/d switch with a toggle switch. He said the trans was rebuilt by AAMCO. Any suggestions? And if anyone is close by, I would like to talk to them.

You mean the speedo drops to zero after 50?

Yes, the needle waivers and then falls.

Sounds like a VSS problem. Make sure the drive isn't stripped and that the VSS is tight.