4r55e no forward, reverse only

[lots-of-fords]

My 96 4x4 explorer with a 4r55e transmission only goes in reverse.
I added sea foam and got it to work in all gears, then I changed the filter and fluid, the truck drove fine with all gears for about 80 miles, I tryed to drive it the next day and reverse only no forward gears again. I tryed adding sea foam again with no luck this time.
This is the 2nd transmission we have tryed in this vehicle, the man we bought it from said "it worked fine" two years ago when it was removed.

 

[BrooklynBay]

It sounds like a valve body or gasket issue. Reverse has more pressure than drive, so that might be one reason why it's working in reverse only. A 0-300 PSI test gauge would come in handy for testing the pressure in all of the gear ranges. Some internal passages in the valve body could be blocked. Some spool valves might be stuck or the EPC might be failing. Did you test the range sensor to exclude the possibility of an electrical problem? Do you have a flashing overdrive light or a check engine light?

 

[lots-of-fords]

I have everything flashing, well everything but the turn signals that is. The check engine light shows a missfire on 3 and once I had a code 500 speed sensor A problem, since this last transmission change. The check gage light is on constantly, I think thats due to a bad oil pressure sending unit. The OD light started flashing one time and thats when I got the speed sensor code. And the air bag light is on, but other than that it is a really nice vehicle.....
Update, I tryed the 4oz of brake fluid trick in the transmission and now it will drive, kind of. I have to start out in low 1 then as soon as I start moving I can shift into drive and it will go into all gears without slipping. If I try to take off in drive it acts like it is slipping.

 

[lots-of-fords]

I looked on Ebay for a rebuilt valve body and it appears that a 5R55E valve body will work in the 4R55E transmission, is this true or should I look for a 4R55E valve body?

 

[BrooklynBay]

The hole spacing on the separator plate is different in one location. The EPC & TCC solenoids are different. The 4R55E uses a green band EPC, and the 5R55E uses a red band EPC. The 4R55E doesn't use inductive signature on the TCC, but the 5R55E does. The external range sensor is different on both transmissions too. It's possible to swap valve bodies with some modifications.