Transmission Shifting Hard

[Billy McIntyre]

This is my first post here and glad I found the place. I have a 1995 Explorer Eddie Bauer, that I have owned for 2 years. When I bought it, it had 196,000 miles on it. It now has about 205,000. Here are my problems. On 2 separate occasions during the last year, the O/D light has come on and flashed for 2 or 3 days and then gone off. When it was on in the past, it seemed the trans shifted a little harder. But once going off I had no problems. About 2 weeks ago, I noticed that my trans started shifting hard going from all gears, it's almost like a thunk when it shifts, you can feel it, it shifts at the right RPM's but just makes a loud thunking noise when it shifts. It started out it was only the lower gears and when shifting to higher gear and overdrive it wouldn't do it, but now it's basically doing it in all gears. The strange thing is that this problem is sporadic. I can get in it and drive if for a while on some days and there are no problems until I drive for a while. I'm hoping it's electrical as basically this is a work vehicle that I have very little invested in it. I've heard of PCM problems and solenoid problems. Can anyone give me a guess as to what they think it might be? I will be taking it to a shop in a few days to diagnose and I would like to be informed as possible to make sure I don't get stuck with an unnecessary replacement job or rebuild. Thanks for any help anyone can give.

 

[Glacier991]

A hard shifting 4R44/55 can be a number of things...so let's check them out...

To begin.... maybe a mention of FMEM is in order. FMEM stans for Failure Management Effects Mode. In short when the computer thinks things may be slipping based on inputs it is measuring against each other, it signals the transmission to UP the hydraulic pressures it uses for shifts and things to help keep "stuff" from slipping. Result? HARD SHIFTS. Usually accompanied by the dreaded flashing OD light.

This transmission, like most these days, uses electronically controlled solenoids (think of valves if you will) and they open and close by signal from the computer. A few special ones can even do tricks. The "Electronic Pressure Control Solenoid" (EPC for short) can even vary transmission fluid pressures internally on the fly via the computer's commands - hence engineers and electronic geniuses were able to fashion FMEM. A very neat trick.

Anyway...the first thing to check in your situation is the pressures within the hydraulic portion of the transmission... the EPC specifically. The EPC solenoid is a notorious failure mode in these trannies, and at your mileage, certainly a possible culprit - you have about twice the common failure point on yours, assuming it has never been replaced.

The EPC lives in the valvebody, or main control of the transmission, and it is full of valves (spools in the trade lexicon) and springs that can hang up or get stuck in older transmissions, causing problems. Main controls are sensitive to being screwed into place very precisely.... and loose bolts can lead to problems as well (crazy eh?).

Also, since the EPC takes it cue from the computer, various "bad" inputs to the computer can cause it to make bad commands to the EPC. Examples include: Throttle position sensor, RPM sensor, Vehicle Speed sensor.

Now you said you have had a flashing OD light. That is the computer's way of telling you it sensed something amiss, and it stores the code that will pinpoint to a degree the system or area where it sensed something awry. Even after the light stops flashing, that code is stored for about 60 starts and shut downs of the vehicle. That numeric code, which can be retrieved from storage, is golden. Best place to start in fact is to see if there is a code present.

So, get the codes read, bring us the NUMERIC CODE (not the daffynishion some jackass gave you) and we can start this diagnosis from there. A pressure check can be done without removing anything from the vehicle. A valve body or EPC check might require removing the transmission pan is all. (Good shops with proper equipment can check the EPC electronically without removing anything.)

Is there a hard parts problem possible? Yes, forward clutch comes to mind, but it is more likely something else....

All that said... your tranny has given you great service, and before I poured a lot into other fixes, I would evaluate its age andprobably lifespan best case, and match that against your driving.

 

[Billy McIntyre]

Glacier...the funny thing is the O/D light is not currently flashing and hasn't done so in probably 3 months. It did do it on 2 separate occasions but only for a couple of days at a time. The strange thing is that this problem is so sporadic...that's why it makes me think it's an electrical problem with the trans...example: it's been having this problem everyday, tonight I drove to pickup my daughter and it shifted hard the whole time...but I stop and get gas and when I got back in it and took off it never shifted hard the rest of the trip home...smooth as can be. Since the O/D light has not been on for quite a while, is there still a chance a code may be stored? Thanks for your help.

 

[Glacier991]

The computer stores codes for a specified number of "drive cycles"... and I have never comitted that number to memory.... seem to recall about 60 or so... (a drive cycle, oversimplified is a ...start... drive.. stop...shutdown).

Maybe someone can chime in and refresh us. But if it is a daily driver, 90 days may be beyond the drive cycle storage limit. Also, sometimes codes can be stored without setting off the OD light.... not common, but can happen.

If everything is ok currently, I'd change the fluid and filter, baby it, and next time you get the light, pull the codes. They may exist anyway.

My guess is your EPC is going south.

 

[BrooklynBay]

Welcome to this forum! It might still be stored if you didn't clear any codes with a scanner, or disconnect the battery. Not all scanners are able to read Ford proprietary codes.