Until recently, my 1994 F150 (2WD) has always had snappy shifts, and been very compliant. (It has the AODEW/4R70W transmission.) I maintain the truck meticulously, and while the transmission has high miles (264K), frequent fluid changes (every 15K), heavy duty cooling, deep finned pan, and an external filter have kept it in perfect order.

Recently, I began to have an issue where under light throttle, the transmission would refuse to shift up at low RPMs, unless I lifted my foot off the gas pedal a little. Under WOT in higher gears, the transmission would refuse to "kick-down", and the engine would simply rev to the sky. I should point out that this was not an issue that got progressively worse. It happened all of a sudden.

Simple, I thought. "It's older and needs a freshening up."
So I replaced:
1) The torque converter with a high quality Precision of New Hampton converter.
2) EPC solenoid
3) TCC solenoid
4) 2-3 Accumulator piston and spring
5) Dual shift solenoid
6) New Mercon V fluid, filters, etc.

I buttoned it all back up, and it acts exactly the same as it did.
Any clues? Is there something glaringly obvious I am overlooking?
Thank you very much for any help you may be able to provide. I am literally at my wit's end.

 

Transmissions wear out when they wear out. Changing the fluid doesn't extend the life of one a bit and around 250,000-300,000 is about the life expectancy of those. Years play just as much of a role as miles. Most REPUTABLE shops now are advising people to skip the fluid changes and just drive them until they need to be rebuilt. It will happen at about the same miles regardless. But there are some shops out there who will gladly take your money and do it. With the money you've spent on 15K oil changes and other repairs you could have had it rebuilt. It's time.

 

Few years back my 95 4r70w started doing a 3rd to neutral shift. Replaced valve body with a reman from Sonnax, this fixed the problem. It was $300 so I figured it was worth a shot, phase two would have been rebuilt trans. My exact problem and solution were well documented by others, yours my not be so clear cut. It might be rebuild time.

 

Guessing blindly is a waste of time, money, & effort - as you've just experienced. Take it to a local transmission specialist (or 3), and ask for professional opinions. The caption of this diagram explains how the transmission is controlled:

(phone app link)


If you want to try some actual diagnosis yourself, read these captions:

(phone app link)


(phone app link)


(phone app link)


Try to disturb as LITTLE as possible when testing.

 

It's a 25 year old truck with 264K on it. Old boy is just worn out.

 

Thank you, all, for your responses. I was hoping since it was an issue that spiked up out of the blue, that something simple (and cheap) might be culprit. Sadly, I'll have to hang my hat on this one.
Regards-