My 1999 e150 with 160,000 miles just started stalling out engine when I put it in reverse or drive. Let the engine warm up to check trans fluid (looks like full) and the problem has gone away. Need the vehicle for work everyday. Was wondering if anyone had similar issue or diagnosis of problem transmission shifts fine when I can move vehicle . Any help would be appreciated thanks

 

It is entirely possible you don't have a trans problem, but an engine problem. From what I can gather, this takes place only when the engine is cold and placed under a load such as putting it in any gear.
The idle speed may not be responding to the additional load. Do you get a similar response when you turn on the A/C without putting it into gear right after starting ?
If not, then possibly the PCM isn't getting the signal to increase idle speed or isn't responding to the signal when cold. What kid of maintenance has been done to the vehicle in regard to plugs wires etc. ?