2001 expedition, 198,000 miles. Got p0781 code ,1-2 shift error. replaced the accumulator valve with a factory tech valve body. Pan was clean, some gray material on the magnet but not bad. 1-2 worked fine after accum swap,but when trying to shift from 2nd to 3rd gear, the transmission downshifts hard all the way to a stop, like the brakes are on. I can manually drive in 1st and and 2nd but when I put it in drive it will downshift/brake instead of shifting from 2nd to 3rd. pulled the main valve body and 2-3 and 3-4 shift valves seem good, no sticking. 3 other valves were sticking. i think they are the Soleniod regulator valve , and coast clutch shift valve, and low/rev modulator. Could they be causing the hard downshift/braking?
Was thinking of cleaning the valve body or just getting reman from ebay but dont want to throw parts at it if this is a known failure. Thanks for any insight. Great forum for learning
Bob

 

Yes, if those valve are stuck that can cause the transmission to bind like that, but it's rare to have so many stuck valves and no signs of metal contamination.

 

James,
Thank you very much for your response. The only metal i saw at all was a single, small staple size piece in the pan. Accumulator 1-2 valve was sticky.(as well as the ones in original post on main valve body). I think i'll clean my main valve body or get the reman from ebay and give it a try. Any thoughts on what else it could be causing this inside the transmission?
Thanks again for your help. Bob

 

Well tried to clean out the main valve body, no change. Expedition shifts from 1st to 2nd. Then it downshifts hard, enough to squeal tires back down to 1st gear, like the brakes are being applied hard. Saw no metal in the valve body at all. I replaced the neutral saeftey switch and the speed sensor in the rear differential. An more ideas?
Thanks, Bob

 

Did you not have the bind up before the replacing accumulator valve body?

If not maybe put your original one back on, you can more the updated springs from the new one to the old one if you want. Also maybe a check ball moved out of place behind the separator plate.

 

It did have the bind up, (downshift/braking ) before i changed the accumulator. It gave the p0781 code,(1-2 shift error), I thought the problem was going to to be the accumulator valve body, so i swapped it out. Then I thought it was going to be the 2-3 valve stuck in main valve body but that valve looked good, no sticking, and it downshifts/brakes instead of just revving up and not going into 3rd. Could it be shift solenoids or tps?
Thanks again for your help and time
Bob

 

Drove truck again tonight. Same thing, went a bit faster, when attempting to go from 2nd to 3rd, car downshifted very hard skidding tires for 10-15 feet. transmission seems like it goes back to 1st. OD light started blinking a steady on-off blink. Pulled codes and got a p1000 & p0782, no 2 to 3 shift. Any ideas? Thanks
Bob

 

A bind shift like that happens when two components are applied when they shouldn't be, like two gears fighting each other.


If you look at this clutch and band application chart you will see that the Intermediate one-way clutch changes from holding to overrunning when the transmission shifts from 2nd to 3rd. I also would think reverse would have issues as well if the one-way clutch was locked on.

If you are sure about the valve body, separator plate gaskets and check ***** its staring to look like you will have to pull this transmission out and take it apart because something is stuck on.



If you had a solenoid problem the only thing that would come close to what you are dealing with would be solenoid "1" stuck on, this would cause the transmission to shift like 1-2-2-1, but going back to 1st on the 3-4 shift it shouldn't feel like the brakes are being applied so I dont think this is where the problem is.

 

Thanks James, I drove truck again today. As I felt it try to shift from 2nd to 3rd, I gave it a little gas, trying to slowly power through the bind up that was preventing going into 3rd gear. It actually seemed to work as far as getting it to go into 3rd and fourth. However, now the 1-2 shift is as it was before. slips to about 3500 rpm then goes into 2nd but will continue to 3rd and 4th. The p0781 code (1-2 shift) came back as well as the slow flashing od light. Reverse, manual 1st and manual 2nd have been just fine.
Thanks agiain Bob