Tansmission not shifting into overdrive

[ronkbrooks]

I have a 1996 Explorer XLT with a 4 speed auto that won't shift into overdrive. The od light flashes and I had codes P0755 & P0756 on it. I was told the transmission was rebuilt less than 15k ago. The book I have says solenoid B malfunction on P0755 and solenoid B stuck off for P0756. Which solenoid is this referring to and is this most likely the problem? Any help would be appreciated.

 

[imp]

I have a 1996 Explorer XLT with a 4 speed auto that won't shift into overdrive. The od light flashes and I had codes P0755 & P0756 on it. I was told the transmission was rebuilt less than 15k ago. The book I have says solenoid B malfunction on P0755 and solenoid B stuck off for P0756. Which solenoid is this referring to and is this most likely the problem? Any help would be appreciated.

P0755 is "Shift Solenoid No. 2 Circuit." This means electrical malfunction was detected.

P0756 is "Shift Solenoid No. 2 Performance".

I don't have the info. for 4R44 or 55 transmission, mine is later, that's why it numbers the solenoids instead of using letters. The solenoid involved is the same, though. Shift Solenoid "B" or "2" causes the transmission to shift into 3rd. gear, not 4th (overdrive). What makes you feel you are not getting into overdrive (4th. ) gear?

When solenoids go blinky and the PCM detects it as electrical failure-caused, it's usually just that. Mechanical failures within the transmission are harder to pinpoint, thus while trouble codes are a wonderful tool, they are not infallible.

If the trans. WAS rebuilt 15K ago, the solenoids may NOT have been replaced, thus failure is possible. Your transmission has individually-replaceable solenoids, so, for a hundred bucks or so, a replacement solenoid given the circumstances, is likely a good bet. BUT, first, it must be clarified as to whether or not 3rd. GEAR is engaging. imp

 

[ronkbrooks]

So, I removed the pan and valve body off. Ohmed out all they solenoid and they where within spec. Swapped the shift solenoid from one side to the other (to see if this would change the codes but it did not. After ~15 second of running the O?D light starts blinking. Check code right away and P0755 came back. Shifted very badly (same as before) and then code P0756 comes back. I noticed the wire harness the connects to the solenoid has a few small breaks in the insulation. Could this be an issue? Also once the O/D light starts blinking does the transmission go into limp mode and could this be why the shifting is so erratic? Feels like it goes from 1 to 2 but I can't tell if there is any shifting after this.

 

[imp]

So, I removed the pan and valve body off. Ohmed out all they solenoid and they where within spec. Swapped the shift solenoid from one side to the other (to see if this would change the codes but it did not. After ~15 second of running the O?D light starts blinking. Check code right away and P0755 came back. Shifted very badly (same as before) and then code P0756 comes back. I noticed the wire harness the connects to the solenoid has a few small breaks in the insulation. Could this be an issue? Also once the O/D light starts blinking does the transmission go into limp mode and could this be why the shifting is so erratic? Feels like it goes from 1 to 2 but I can't tell if there is any shifting after this.

No. Your tachometer should reveal as the vehicle speed is gradually brought up under minimal throttle, whether a shift occurs after second gear is achieved. First drop in rpm indicates 2nd. gear attained, If no drop occurs after that, when you judge from previous driving experience, then likely 3rd. gear has failed to engage.

Breaks in wiring insulation are not good. I would determine which wire feeds shift sol. B and check it's continuity back from the connector at the transmission to the PCM connector. If no continuity in that wire, the solenoid gets no juice. imp