I have an 05 expedition. Its 2wd and the transmission will go into gear and i can take off ,but as soon as i slow down or stop, its like its in neutral.
I can wait a little while then it will do the same thing.
it has fresh fluid at the correct level and a new filter.
when it first started acting up i was on my way to work its about a 30 mile drive. It acted like it was trying to slip in and out of gear but just slightly. When i got into it and put it in gear after work it moved about 100 feet and that was it, no forward gears only reverse.

 

 

the trans was rebuilt about 10,000 miles ago and of course the warranty has run out. The problem started about 2,500 after service. The service was done after a trans line blew alot of the fluid out on a road trip. Decided to go all new fluid and filter after replacing the line.