4R55E with code P0756

[lapetec]

96 Exp XLT, 4R55E
P0756 Shift Solenoid B Performance or Stuck Off

I've read a lot about code P0756 on this forum but still not sure where to start.
The trouble started with the trans not wanting to shift in to 2 gear until you let off the accelerator.
After a few miles the OD/Off light starts flashing and then get a hard shift into 2nd. 3rd and 4th gears seem to shift normally.

There seems to be no engine braking in 1st or 2nd gears and doesn't want to down shift to 1st under acceleration.
Strangely. sometimes it will shift into 2nd gear normally when accelerating up a hill!

Today after a long drive it stopped shifting up from 1st at all. I discovered if I shut the engine off
(resetting the computer) and restarting the engine the trans will up shift with the same symptoms as above.

Recommendations please.

bump

 

[greasemanicure]

ATSG says...

The ATSG manual that is linked to on this forum says that the P0756 code would indicate a loss of 3rd gear, not exactly the balking at shifting out of 2nd that you have. I have the same code but 3rd "seems" to be OK but I have major slip taking off in OD or Reverse. Killing OD seems to fix forward but reverse still stinks.

I'm in the process of checking pressures at the line port.
Joe

 

[mwant0276]

transgo kit?

 

[PopRichie77]

lapetec,
Drop the pan look for pieces of blown out valve body gasket, if non found, check the bolts for tight with a INCH LB torque wrench, replace shift solenoid #2, (B) and change the filter, add new fluid till full on dipstick with engine running and trans in park, if this doesn't fix it there are other issues.
The difference in the driving is because the computer goes into limp mode.

If you find the valve body bolts loose the valve body has to be removed.

 

[too_many@verizon]

I have a 1996 4.0 Explorer XLT. I have been around the block on this problem. The specific physical symptoms are; no 2-3 upshift unless I manually start out in 2nd then shift to Drive a bit late or starting out in Drive, let 2nd run up to 3500 rpm, let off the gas pedal completely and get back in the gas when I feel it shift. Then the 3 – OD shift and converter lock is normal.
Electrical symptoms include MIL light and code P0756 and occasionally have the OD light flashing which indicates the vehicle is in limp mode.
So far I have had 2 different valve bodies in it due to what I have seen looking at many forum posts and Ford TSBs, no improvement. Today I got technical on it having purchased a Ford transmission troubleshooting book by Mandy Concepcion. According to the information in the book, the 4R55E trans. shift solenoid combinations are;
1st gear- only Sol. 1 is on
2nd gear- Sols. 1 & 2 are on
3rd gear- All Sols. are off
4th gear- only sol. 3 is on
The solenoids are supplied battery voltage and the PCM supplies ground to activate them. (Shift Sol. 1 = PCM pin 27, 2 = pin 1, 3 = pin 53) looking at the firewall pin 1 is on the bottom left, I back probed it and used my Fluke meter on a drive test (it will read Batt. voltage when off, and around 200 - 300 mv when on) my trans is doing what it is told to, my PCM is not releasing the #2 or B solenoid when it should (since for 3rd gear all solenoids should be off) when I drag 2nd out and release the gas (and wait...) I see the meter go back up to 14V and there's 3rd like it should be.
Now the question is, do I need a PCM or is there another reason the (faulty input from another sensor maybe ?) PCM doesn't make the 2 -3 upshift when it should. I checked the TPS with my Fluke 97 scope, tapping the sensor w/screwdriver handle, smooth trace. I will try to find a bone yard PCM to try.
I hope this helps.

 

[too_many@verizon]

I found an exact P/N match on a used PCM, still having the 2 - 3 upshift problem and got a code P0756 after 5 min. drive test. Bad used PCM with the same problem is possible.

Has anyone seen this issue resolved?

 

[NavyHeloGuy]

too many@verizon,
Did you ever get this resolved? Having very similar issues on my 96 Exp.

p0756, O/D Off flashes if I take it over ~50 mph.

Spent a cold Saturday on my back in the garage last Saturday: dropped trans pan, no debris, replaced SS2, checked continuity on all 16 pins of the internal wiring harness, reassembled, reserviced, and got the same no shift from 1 to 2 unless I let off on the accelerator. Shifts normally from 2 on up. Above ~50 mph, O/D Off light starts flashing.

I checked adjustments on the bands and was surprised that the second one going toward back on the trans did not "tighten" as expected. I stopped running the bolt in long before I ever encountering resistance, much less reaching 120 inlbs. Sinse I didn't find any debris in the pan, I didn't expect the band to be broken. Don't know if there could be another explanation for this.

With second band broken would it even shift into 2? Is there another means of determining if this band is broken, like by shifting into 2 instead of D and starting off from a sandstill?

When this problem first occured I read every post I could find from BrooklynBay and Glacier99. These gents seem to be very knowledgable. I will try to connect with them to see if they have any suggestions. There are a lot of posts on this problem but I saw very few "this is how the story ends" posts that identified the specific problem and what they did to fix it. Hope there are some answers out there.

Respectfully, NHG

 

[JK080]

\

I checked adjustments on the bands and was surprised that the second one going toward back on the trans did not "tighten" as expected. I stopped running the bolt in long before I ever encountering resistance, much less reaching 120 inlbs. Sinse I didn't find any debris in the pan, I didn't expect the band to be broken. Don't know if there could be another explanation for this.

If you turned the adjustment bolt in and didn't tighten the band, its probably broke. You should be able to see it if you remove the pan, the band and anchor and the adjustment bolt can be seen from inside just in front of the manual linkage inside the case.

 

[NavyHeloGuy]

JK080,

Thanks for the reply. I should have checked that before I put everything back together. I suspect you are right as much as I hate to face that reality. Will have to wait until after the Holidays to get back under there.

Is there any other way to independently verify if the Intermediate band is broken?

 

[BrooklynBay]

A band adjustment or physically dropping the pan to inspect for broken parts are the only two ways to check for a broken band (other than tearing the transmission apart).

 

[too_many@verizon]

It seems my situation is that I do not get a noticeable shift from 1st to 2nd which is causing the P0756 code and the need to let RPMs drop way down to get the shift into 3rd (All is fine after that), Did all of the wiring checks, no broken parts in the pan and replaced the valve body using the bonded separator plate/gasket. I recently did a band adjustment on both bands no change. I am going to replace the intermediate servo, just got it. fingers crossed.

 

[GtnAwyMrdr]

Did you ever find the fix? I recently acquired an Explorer with the P0756 code.

 

[NavyHeloGuy]

GtnAwyMrdr,

Regarding "Did you ever find the fix? I recently acquired an Explorer with the P0756 code.", I found the problem with my 96 EX did and it wasn't what I was hoping for.

I dropped the Transmission Pan a second time and found that the intermediate band was broken. With the band broken, the adjustment Pawl that engages the band for keep it at the right tension was just laying in place (had not dropped down into the pan). I pulled it out with my fingers.

Only options were to junk the EX or get the transmission rebuilt. Logically, the choice was simple, junk it. Emotionally, get the trans rebuilt. Guess which way I went!

I've owned it since new so knew every thing about its history. Had two kids about to start driving and wanted something safe and reliable. So... dropped $2000 on a rebuild, 36 month, 36,000 mile warranty. So far, I'm glad I did it.

Good luck