For the past 6 months my bronco has been upshifting hard. hardest from 1-2 but still hard in 2-3. What I'll do to fix it is unplug the battery over night and connect it the next day and it works for about a month shifts smooth like normal but than it starts shifting hard again. So i'm thinking it's obviously not a mechanical issue because it resets after the battery is unplug, but anything after that I'm clueless. Even before this happened 6 months ago, when put in 4x4 Lo it would shift the gears hard as well but not too bad. Is that normal? Its done that for the 3 years ive owned it.


-94 bronco 351w auto-

 

man, i've had the exact same problem...and poured and poured over this site and not found a fix. it's hasn't seemed to cause damage. it's just annoying. have you found a solution yet?

 

What type transmission? The OD cancel on the grear shift? Then E4OD, and you can get codes for the transmission just like the engine.

 

How long since you pulled the pan, drained the torque converter, replaced the filter and added about sixteen quarts? Is your speedometer accurate as it will improve shift points? Even though not showing any codes, replacing just about every original sensor and ignition stuff resulted in a great running engine and smooth, earlier shifting. If your oxygen sensor has 60K on it you might replace it and get lucky. A good running engine improves the transmission drivability. Since it is a 94 it probably got the warranty upgrade on the E4OD like mine. Check with Ford to be sure.

 

thanks.

the only sensor i've changed is the VSS. which was easy. didn't fix.
this is about as spot on as i've found:
https://www.ford-trucks.com/forums/3...d-problem.html
"The fuel injection computer regulates transmission line pressure using the EPC solenoid.
If the computer finds certain inputs not to its liking, it can put the transmission into "performance mode" -- it raises the line pressure to the point that the transmission shifts hard. This is especially noticeable on the 1-2 shift.

Performance mode is an endeavor to protect the trans. The higher the line pressure, the harder the shift, and the less slipping of clutches and other internal components. Hard 1/2 shifts caused by typical "performance mode" will not damage the trans; though the situation is annoying and you may think that damage is happening.

Pulling codes can sometimes get the computer to reveal what sensor it thinks is out-of-spec. The most common culprit is the MLPS on the side of the trans -- the early design was susceptible to water splashing and corrosion. The next most likely possible problem area is the VSS sensor -- if the computer thinks the trans is slipping because the VSS input is not consistent with engine RPM it will go into "performance mode". A worn torque converter clutch is another more distant possibility -- too much slip = performance mode. The TPS on the throttle body is another possible, albeit unlikely, suspect."

but i dunno much.

thought's on changing the MLPS?
oh and recently changed filter and fluid. speedometer seems accurate.
94 5.8 eb E4OD

 

I'd still pull the codes. There are several things the transmission will report.
MLPS, Trans Temp, Soleniods, and the biggee...Electronic pressure control failure...(code 99)

 

i'll go do that now and reply tonight. thanks!

 

i assumed i could get a parts store to pull the codes.
the two parts stores i went to...neither said they had the proper instruments to pull the codes.

guess i'll try a transmission shop.

 

If you have a volt meter. I have a Simpson analog sweep model. You can pull your own codes.


All you will ever want to know abot your EEC-IV system...

Ford Fuel Injection

 

You can pull codes with a paperclip if OBDI.

I had similar problem, code pointed to faulty vss.
Replaced vss, no fix.
Checked wiring to vss, no fix.
Replaced PSOM, problem solved.

 

it can be a number of things. the sensor on top of the rear diff, MLPS being bad, TPS, low fluid, a dropped tranny filter etc..

pulling codes for both the tranny and motor should be done. tranny service.

 

code video.
here's the blinking light...tried to read it. didn't feel confident.
thoughts?

this is what i got.
III III I IIII IIIII II IIIIII II IIIIIIII II II IIIII II IIIIII II IIIIIIII

i dunno.

thanks!!

 

I see 11-11 all good. Stored codes. 45,26,and 28.

See what others see. Run your codes on the web site. My stuff is for through '87.

Bob

 

The '94 has three digit codes. I could not decipher it either. I gave up and bought accuracy. There is a great digital display code reader for about $35. It totally eliminates the guessing.

 

What I read is:


452
Computer detected an error in the VSS or PSOM signal during the last 80 warm-up cycles


628
Converter clutch Lock-Up error (E4OD)