Servo pin wear on the bore of 5R55W transmissions? | Ford Explorer Forums - Serious Explorations

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Servo pin wear on the bore of 5R55W transmissions?


Explorer Addict
July 20, 2002
Reaction score
City, State
Southeast USA
Year, Model & Trim Level
2000 Sport
Does anyone have info on this problem? It's a big topic on another forum, but I don't find much here using a search.....

It seems the steel servo pin wears out a groove in the aluminum servo bore, allowing a pressure drop and causing slippage and no-shift into upper gears.
AFAIK, it shows up on the 5R55W models, 2002 and later.

Will this be a future problem with my 2000 5R55E, that I need to lose sleep over?

(By the way, I was one of the first to do the 2-3 shift flare fix on mine at around 50K miles; the trans now has 112K on it with no problems since).

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Yeah that is a big issue with the 5R55W. The rebuilders I spoke with are seeing lots of these transmissions with the servo case problem starting around 70K to 90K.

The repair seems to be either "ream out the case and install bronze inserts" or send the case out to a machine shop and have them to the same thing. Guess it depends on how comfortable you feel about inhouse vs. a machine shop. Obviously the transmission needs to be pulled and rebuilt.

The other issues about the 5R55W have been covered by BB and Glacier (solenoid block, valve body gaskets etc.)

This issue is mostly with the 5R55W, and later transmissions. Other transmissions could have this issue too, but on the 5R55W, the servos are much more massive in comparison to your 5R55E, so don't worry about it. Sonnax makes the bore repair kits. Check WWW.Sonnax.Com for more information.

Here's a link with more information:


This is a shot of the overdrive bore on a 5R55E out of a 2000 Ranger with a little under 100,000 miles. Notice the ridge the pin has worn on the bottom of the bore. It's very similar to the wear on the 5R55W/S/N's, and AX transaxles.


Is there a way you can place an arrow or some sort of identifier on your pics? Its hard to make out when a trans amateur like me doesn't know what he is looking for. (or at :D)

OK Here is my situation...I too had the P0732, P0735, and P0775 codes and delayed shifting 1st to 2nd.

I have first changed the fluid and filter. Problem still there.
I then replaced the solenoid block and valve body. Problem still there.
I re-torqued the bands. Problem is still there but it does shift a little sooner.

I do feel that the servos need to be bored and sleeved, but I am not doing that myself. I may try to find a shop to do it, or Ford themselves. About how much is the cost on this?

I was going to try to tighten the bands another 1/4 to 1/2 turn as someone mentioned to me.

Also, people mentioned an additive to be put into the fluid. What is the additive? What does it do? Where can I get it?

I am very disappointed with this situation right now and am ready to sell unless I can get a guarantee that this will solve my trans problem.

BrooklynBay & Glacier991...Can I get your input on this? Thanks!

Welcome to this forum! You should remove the transmission from the vehicle, and disassemble it before you rebore it. You wouldn't want to get metal filings inside, so the best thing to do is remove everything from the inside to work with an open case. A transmission shop could check the bores while the transmission is still in the vehicle, but it's very difficult to get to that area. The catalytic converter would have to be removed, and even then there is limited space. Not every transmission shop is equipped for this repair since a special jig is required. They might give the case to a machine shop. Check WWW.ATRA.Com for a shop in your area. The parts could be obtained from WWW.ServoBore.Com. This link will show you how to do this repair:


2002-2005 Thunderbird
2005-2009 Mustang
2002-2009 Explorer
2007-2009 Explorer Sport TracLINCOLN:
2002-2006 Lincoln LS
2003-2005 AviatorMERCURY:
2002-2009 Mountaineer


Some 2002-2009 Explorer, Mountaineer, 2007-2009 Explorer Sport Trac, 2002-2006 Lincoln LS, 2005-2009 Mustang, 2002-2005 Thunderbird, and 2003-2005 Aviator vehicles equipped with a 5R55S, 5R55W, and 5R55N transmission may experience shifting concerns. A loss of 2nd, 3rd, and 5th gear may have overdrive band or intermediate band failures due to servo pin case bore wear causing reduced apply pressure.

There is no need for a machine shop to do this... the tools available make it foolproof even in a tranny shop... but you DO have to drop and virtually rebuild the tranny. IMHO, a quality rebuild will sleeve everything for which an aftermarket sleeve is made for.

I have the same prob on my 02 xlt explorer. I took out the tranny and bought a rebuild kit.

before that i changed the fluid and changes noted
Changed the solenoid bloci..........................made it worse

Now i took it out, but cant figure out how to remove the cap/plate/cover/whatever its called the thing right behind the Touque do i open the transmission................i tried searching but found nothing.

i opened up the servos and the washers on them are broke in to 4 pieces.

The big question: Is it safe to take from the above that if the pressure control solenoid is, in fact, operating that bore is going to be the problem? I just had the symptoms appear last week (though I have no slipping). Shift flare out of first, no OD. Codes are 2nd ratio, 5th ratio, and solenoid B.

I will be doing the resleeving myself (with the help of a trained tech) if need be.

I saw something on e-bay (not there when I just checked) where someone was selling a revised piston that was claiming to fix the bore wear problem by revised piston bore seals.

Anybody seen this fix or know anything about it?

Sure would be nice to avoid the pull the tranny fix required to re-sleeve the bore.

I am the guy on ebay and it works on badly worn bores. The design can take up a tremendous amount of wear, and the entire exposed surface area of the o-ring is exposed to less than 3 lbs of pressure. The second o-ring at the top of the bore improves the performance with respect to back pressure. I have had guys install this in bores with 120,000 miles and it fixes it just fine. Keep in mind the system was designed to work with a certain amount of leakage and even in a badly worn bore the percentage of leakage with the o-rings is less than what it what originally designed to work with.

Welcome to this forum! A while back, somebody joined this site who claimed to be the guy on EBay. We asked him some questions, and he never replied. Anyway, since this now cleared up, I have some questions for you.

1. Why didn't you contact a company like Sonnax who could add this to their product line? They make a boost valve, and valve body end plugs with O rings. I'm sure that they would add your servos with O rings to their prodiuct line.

2. Do you plan on making servos with O rings for other models such as the A4LD, 4R55E or 5R55E transmissions?

3. One member on this site did an analysis of the 5R55W, and concluded that the reason there is irregular servo bore wear on the 5R55W is because the servos are forced to travel at a slight angle (wearing the bore in an egg shaped manner). It's probably some design flaw from Ford. If this is the case, then the O rings will get prematurely worn down on one side. What is your opinion on this? How many miles did your design last before the servos or O rings failed?

4. Would you consider being a vendor on this site for them? You might be able to sell a lot more. Thanks for your time.

Response to the questions

#1 I have not contacted companies like Sonnax becuase I am looking into patents possibly before I make contact with those companies.

#2 As far as making servos for other transmissoins, since I did not have access to those types I had no good way of determining lengths of the bores position of the ports etcetera. If anyone wanted to supply me with the part numbers and dimesions I would be happy to work with them.

#3 There is definitely a design flaw in the transmission lines and Ford should be embarrased. As you say their are forces that push down on the rods which wear the aluminum and eventually the bronze bushings if someone is sleeving them. Since the pins are so hard, the softer metal will always sacrifice.

Beyond that I can not comment much on how it works becuase of the patent. Putting too much information public is a no no where that is concerned.

I can tell you that I actually shaved part of the 0-rings off on the set I am running in my vehicle and after 8000 miles, I have not seen any changes in performance since I put them in.

I may be able to fill people in more soon.

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