Troubleshooting tips needed

[JakePSD]

Truck is an 05 explorer, v6, 4x4. Shifted perfect until the other day it randomly stopped going into 2nd and 5th gear. Rather than go into 2nd, it just keeps revving up until it goes straight to 3rd, then shifts to 4th and locks the converter. By this point the o/d light is blinking and it says "check transmission" in the odometer area. Besides skipping 2nd and not going into 5th, all other gears work normally.

I scanned it and have 3 codes. P0732: gear 2 incorrect ratio, P0735: gear 5 incorrect ratio, and P0775: pressure control solenoid B.

My first thought was the solenoid block. I ohmed out the whole thing using the pcm connector and F-37 cavity and everything came back within spec.

My 2nd thought was a broken o/d band. However I adjusted it by the book (10 ft-lbs, back out 2 full turns) and it torqued down. So that tells me it's not broke. The adjuster seems to be in just about the same position as before the adjustment.

I took it for a drive after the adjustment and there is no change in transmission function and I have the same codes.

What would be my next step? Could a mechanical failure of PCS B be to blame? If so, wouldn't that make all the other gears act incorrectly too? I noticed in my ATSG book that 2nd and 5th gears use variable pressure from PCS B, whereas all other forward gears have lower presure.

 

[transman304]

Have seen this more than once. Good luck.

 

[JakePSD]

Is that the servo? If so, besides removing it for inspection, is there a way to point it as the problem?

 

[transman304]

Yes, that’s the OD servo. With the trouble codes you have the first thing is to check band adjustment. Which you have done, the second is remove the servo cover to inspect the piston. You could also hang a gauge on it and drive it and see what line pressure does on the shifts. Or run it on a lift through the shift pattern..

 

[JakePSD]

Checking the pressure seems easier, but I don't have a gauge that reads high enough. The only gauge I have goes up to 100 psi, and since idle pressure goes up to 110, that seems like a bad idea haha. Looks like I'll be popping the cover off.

 

[JakePSD]

After over 4 hours of just trying to get the damn snap ring out, I have discovered that not only does the servo look like the one in the picture, but the shaft of it is broken off. So once I get what's left of the cover out of the trans (had to break it apart to even get the last 1/3 of the snap ring out) I have to extract the other end of the shaft. Corrosion has gotten to the case pretty bad I'm finding out. The face of the cover is broken off now but now I'm left with the round side that is in the case, and is stuck tighter than (insert inappropriate comparison here).

So any advice on how to get what's left of the cover out would be GREATLY appreciated. As of now I'm probably just gonna chip it apart.

 

[JakePSD]

One other thing that's been bothering me since my last post is what caused it to break? Is my replacement (from a used trans that's taking up space in my garage) gonna break soon after?

 

[JakePSD]

FINALLY!!! I just had to keep carefully using a hammer and punch to spin what was left in the bore back and forth to loosen it.

Thanks for the advice transman. If you are ever near NW ohio I'll buy you a case of your favorite barley soda.

 

[transman304]

Were you able to get the apply end of the broken pin out of the case? As far as if it will happen again, well there are some steps you can take to help prevent this but by no means could you rule out a future failure. If I had a crystal ball and could tell you how long a repair would last I would not be in the transmission business.LOL. At this point your only option is to replace the servo piston. Personally I would put a new part in vs a used piston. That would cut down the possibility of the used part already being stressed from use and prone to break. For the time you have invested at this point a $30 part is some insurance. For what causes the problem, I can only speak from what I’ve seen and my take on the root cause. Once again my personal opinion on this. I am not an engineer and didn’t stay at a holiday inn express last night. In the photo you see the black circle with the band strut. Notice the limited travel space before the strut contacts the band. If the band was out of adjustment the servo would travel farther out and push the strut into the band. As you see from the angle of apply it will push the wedge shaped strut down. The arrow points to the pin that has been bored with a thru hole and as the pin extends further out the weak point becomes the hole thru the pin. The pin breaks through the servo after the pin is broken and the servo will not travel and the transmission senses a slip and will set high line pressure to compensate for the slip and over several drive cycles will push the pin through the piston.

 

[JakePSD]

I haven't tried to get the end out yet. I'm gonna leave it in there to help keep contaminates out until I get the new part and time to fix it. I'll be in and out of town for the next few weeks for work so I won't have time to fix it.

I will take your advice and buy a new one. As much of a PITA as this was, I don't wanna do it again anytime soon.

Everything you said about why it failed seems to be what happened. The piston is in fact broken right at the hole.

The adaptation in the PCM must learn quickly because my girlfriend (it's her truck) never noticed any odd shifting or anything prior to it failing. She said it was working perfectly fine and then out of nowhere it lost the gears. She thought it was a hard 2-3 shift rather than it actually skipping 2nd, but hey, at least she is smart enough to almost properly identify they symptoms.

 

[JakePSD]

I figured I'd update. The local trans shop I use sold me a good used piston, cover and snap ring for $15. Couldn't go wrong with that. Installed it all and it's working great. Let's hope it lasts for a while. Thanks for the help! Much appreciated.

 

[JakePSD]

Just thought I'd add also, I wanted to get a new piston, but time was not on my side. I had to get it fixed by Saturday since I needed my mountaineer back and the woman was borrowing it since it was her truck with the broken part.

 

[transman304]

Thanks for the update. Glad things worked out.

 

[imp]

After viewing these pics, I am preparing for when my 160K 5R55S does this, I will make a replacement piston out of 7075-T651 Aircraft Aluminum, and not worry about stock parts breakage again. imp

 

[JakePSD]

After viewing these pics, I am preparing for when my 160K 5R55S does this, I will make a replacement piston out of 7075-T651 Aircraft Aluminum, and not worry about stock parts breakage again. imp

What about the steel part imp?

 

[imp]

What about the steel part imp?

@JakePSD
The entire piston and rod assembly could be made in one piece, of steel, if desired. The factory made it the cheapest way possible, while considering they had to a million of them.