94 Explorer A4LD Slips from DRIVE to NEUTRAL

[dhinch279]

I have read through several of the How To's and I can't find my exact issue. What happens is I get in the Explorer, start it up, put it in D, drive half a block to the top of a hill and stop at a stop sign. It then feels like it drops into neutral and won't go anywhere for 15-20 seconds, then it will drop back into drive and I won't have to worry about it the rest of the day. It does this probably 3 times a week. The hill in front of my house is pretty steep and of course I park the explorer on that hill everyday. I checked to fluid levels and it checks out fine, so I'm not sure whats next. Any Transmission gurus out there that can help a fellow RBV'er out

EDIT: I read AllanD's sticky, so I will give as much information about the Explorer as I can

1994 Ford Explorer XLT
64,000 original miles
A4LD Automatic Transmission
Electric Transfer Case
BONE STOCK