'99 Expedition AT problem

[manicmechanix]

So a guy I know has a '99 Expedition, 4.6, 4X4, with the 4r70 AT (I'm not a Ford guy but I understand there's a 70 and a 100 ). The transmission now has no forward speeds and only reverse.

He bought the truck not too long ago and has been towing a trailer some with it. He recently drove it a couple hundreds miles towing the trailer and had no the problem, parked it today and later the transmision had no forward speeds.

I checked it out and the fluid was too low to register on the dipstick and it appeared one of the trans oil cooler lines had been leaking. So we put 5 qaurts in it so it'd register on the dipstick. Now you could see the remaining fluid was burned and he still has no forward speeds. So looks like he leaked out/burned up about half the transmissions fluid capacity, and burned up the transmission.

So my question is the transmission problem is one that can't be fixed without pulling and rebuilding or replacing the AT, right? I was also wondering what years would be compatible with this unit from the junk yard.

[MagicRat]

Before changing it, drop the transmission fluid pan and take a look. If the pan is full of muddy-looking debris and the filter looks clogged, try cleaning out the pan and changing the filter.
Then reassemble, add new fluid. Before starting it, remove a transmission cooler line. Start the engine and let the transmission line pump out dirty fluid. When the fluid starts to appear clean, shut off the engine and reconnect the line.
You may have to add additional new fluid to the transmission when doing this.

This has worked for me under identical circumstances.

However, I would give it a 50-50 chance at best that it will fix your problem. However, at this point, you have little to lose in trying.

[manicmechanix]

Hey MagicRat, that sounds like a good tip for cleaning out all the old fluid. I'd assume it would be best to unhook the return cooler line either at the radiator or the transmission to flush out the cooler as well? I'm not a transmission guy but I did a little quick reading and refresh on ATs, and usually when you have no forward speeds, the forward cluth is burned out. I guess the test for this is to check fluid pressure at the forward tap.

Since he had a cooler line leak and the fluid was very low and what was in it was dark and he's been towing a trailer, I'm betting he burned out the transmission. I'm just going to tell him to either get another transmission put in or have it rebuilt. Thanks again for the flushing tip.