1993 Ford Aerostar Transmission selector in Drive Van won'

First of all I like to say that this big extended van has been a good vehicle and hopefully it has not yet seen it's better day although I am somewhat concerned.

Today it is quite cold. The van is started and was put into Drive to move up the driveway for a minute or two, then it was put in reverse and backed out the driveway. Drive was then selected, but there was nothing, the same was true with reverse and everyother option on the selector. At that point the driver parked the vehicle and came back to it in 5 minutes, restarted selected a gear and took off.

This has happened a couple times before. Once the gears decide to engage the thing goes like a scalded dog- no slipping.

Any Ideas outside of a transmission rebuild?

updated 2/27/09
Thanks
I can certainly give that a try. The last filter and Tran fluid was at
80000, over 100k miles ago. I think I may have sealed the gasket to the pan
when I changed the filter previously.

? You think the filter is clogged and the cold viscous transmission fluid
was not readily picked up by the pump?


UPDATE 5-8-2009
I finally change the trans filter and fluid. It is still up to the same thing. My son drove the vehicle today, biabk out of the drive and had to wait for it to catch to go forward. He said it was also delayed when he moved out in traffic.

What next ?