5R55E shift question

[greg s]

Hi, Is there a way to know what gears the transmission is shifting thru and what gear it is finally in? I have a 97 EXPLR SOHC with a shifting problem but cant tell what gear may be the problem. The lower gears and reverse work ok but it seems like its not in 5th gear as the rpm is higher than normal. The last gear that it shifts to will only happen after 45mph (3500rpm) and it flares when it does that. Maybe like the computer is in "limp" mode and it has to be at 45mph or higher. But if I switch off OD with the button, then it seems like its only in 2nd or 3rd gear and the rpm is really high. So its like 5th might be working since the button has an effect on it.

Its has a CVB valve body in it, and I dropped it out to check it, the gaskets and solenoids. Everything looks good and the solenoids all tested fine. I put it back in with new gaskets and it didnt change anything. I get codes for 4th gear and 5th gear ratio incorrect.

 

[JK080]

The only time I dealt with those two codes together was on one that I had rebuilt and it came back a few months later with those codes. I found the release side of the intermediate servo piston had failed and blown out, it was even a new piston. Replaced the piston and fixed it, so hopefully this is what you are dealing with.

 

[greg s]

Thats interesting. Is there any way to test for that? I rebuilt the trans about a year ago and replaced both pistons with new ones. When I had the valve body out, I looked at the bands on both sides to see if one was broken. I used a screwdriver on the adjuster side and could make them tighten, so I figured the bands are ok.

 

[JK080]

Other than air testing the servo but that means removing the valve body again, so it would be easier to remove the servo.

I heard that the National brand that manufacturers servo pistons had a bad batch that would fail like that. I had several 4R70W 2-3 accumulators that failed and it would cook the direct drum.

 

[greg s]

I will definitely look at that. I guess that I can replace the servo without removing the pan? The anchor point will stay in place?

I wish I had a better understanding of what is happening with each shift. I have looked at the charts but it doesnt always register to know what makes 1st gear work, 2nd, etc. I have always tried to use the idea that in order to fix something, you need to know how it works.

So when I turn off O/D and it doesnt shift to the same last gear(?) as it does with the O/D on, does that mean the O/D system is working? And is the problem because one of the other gears is not correct due to the band not functioning correctly?

Thanks for the help.

 

[JK080]

The band anchors are fine because they are indexed into the little cams that the servo pushes on, so you can just remove the servo, you shouldn't really have to even adjust the band unless you use the adjuster to push the servo cover off.

The oil that is used to apply the direct drum must first push the intermediate band off by using the larger side of the servo and spring, so if there is a big leak here the direct drum wont apply and you will lose 4th and 5th. You also have a converter lock up going on too so that can be confused for a "gear".

The direct drum is also used in reverse but the oil is routed differently through the manual valve.

Here is a clutch and band chart that might help you better understand what is off and on in each gear.

 

[greg s]

Thanks for the chart. Now to see how much room I have under there to get the servo cover off. I am guessing that I wouldnt need to check the front band servo?

Also, does the converter lock up create the 5th gear OD? Just wondering what gets turned on/off by the botton in the shifter. That part still seems to work.

What part of North GA are you in? I was up in Lafayette GA over Thanksgiving.

 

[greg s]

So I did a little more testing to see what "gears" are working. So in normal driving on moderate acceleration I can feel it shift 3 times, then it has to be at least 45mph before the 4th shift. If it drops below 40mph then it drops out of the 4th shift. Also the 3rd shift doesnt seem to have engine braking.

If I turn off the OD it goes thru the same 3 shifts and will not make the 4th shift. But in the 3rd shift it does have engine braking.

I also did the converter stall test and it "passed" at around 2600 rpm in each position.

 

[greg s]

Finally had the chance to work on the transmission and you where 100% on the mark. I got the intermediate servo out and found that the lip on the large o.d. was split in one area. So much for "new" parts. Since I wasnt sure if it was going to be the problem I didnt order a new one, but swapped in the old original one I saved from the rebuild. I guess if I decide to replace it again, I should order one from Ford. Thanks again for the help.

 

[JK080]

Nice!

Looks like you dodged that bullet, the one we had I had it pulled out and found the servo failure when I was tearing it down. After a quick inspection on the tranny I just put it back together with a new servo.

 

[greg s]

Thank you again. I was not looking forward to taking the transmission out! It was disappointing to have a problem with the transmission only a year after rebuilding it, since it worked so well. The servo is a National brand. The original used one I swapped in was definitely harder but seems to work ok. I wouldnt mind replacing it again with a new one, but am concerned with getting another "bad" one from National. So I guess I would have to order one from Ford.