5R55E reverse servo pin cracks?

[BK_89iX]

Didn't notice these until I was wiping things down in good lighting.

Are these cracks on the tip of the reverse servo pin going to be a problem?

What's the root cause and what's my best course of action?

BK

[PopRichie77]

It should be replaced as pieces are likely to break off. I don't know the cause, could be a bad heat treat in manufacture, too high of reverse pressure or just stress cracks from high mileage use, it is also used for manual Low. Also check the band for any cracks as they break often.

[BrooklynBay]

Make sure that you get the correct lenght servo as your replacement. Check WWW.Wittrans.Com, WWW.BulkPart.Com, WWW.TransmissionPartsUSA.Com & WWW.EBay.Com.

[BK_89iX]

Originally Posted by BrooklynBay

Make sure that you get the correct lenght servo as your replacement. Check WWW.Wittrans.Com, WWW.BulkPart.Com, WWW.TransmissionPartsUSA.Com & WWW.EBay.Com.

Sounds like a new piece is definitely called for here.

I've seen descriptions of "0, 1, 2 bands" for this part. Presumably that is the length code? My pin has a single machined groove near the base (maybe this is the length designator?).

Numbers on the bottom of the piston are:

D3A9A
1271.A.04
74DT
7A266AC4

How do I interpret these numbers for ordering purposes??

BK

[BrooklynBay]

Check these links:
https://www.wittrans.com/SchematicPa...E&LinkCode=910
https://www.wittrans.com/SchematicPa...E&LinkCode=912

I recommend the TransTec D ring kit to replace the standard O ring seals: http://www.transmissionpartsusa.com/...-00023256k.htm

[BK_89iX]

Many thanks for the details. I think I'll order #912 with single groove - for once a very reasonably priced part!

Is there a corresponding FMC part number? Not sure how to decipher the numbering on the cracked piece. I have some dealer items on my list as well.

Already ordered my servo D-rings two days ago based on endorsements here!

BK

[BrooklynBay]

Try entering the Ford part number on WWW.TousleyFordParts.Com or WWW.GreenSalesCompany.Com.

[BK_89iX]

Originally Posted by BrooklynBay

Try entering the Ford part number on WWW.TousleyFordParts.Com or WWW.GreenSalesCompany.Com.

After some investigation it seems the Ford pn for the common "single groove" length version is D7ZZ-7D189-A. If that's the correct pn it's been in use across various transmissions going back to the '70s!

BK

** Current single-groove low/reverse servo piston is pn XL2Z-7D189-CA and $33 from the dealer. **

[BrooklynBay]

A lot of parts are interchangeable since the basic design is very old. The C3 morphed into the A4LD, then became the 4R & 5R series.

[CDW6212R]

Check Tasca Ford for parts, they are the biggest online dealer, one of the oldest, and strive to stay the biggest. Overall they are the cheapest, and can find some obsolete parts.

[BK_89iX]

Got my new reverse servo today from Tousley.

Checked all the dimensions with a caliper and it looks correct. Year code in the casting looks to be 11, so I guess it's recent and not NOS.

Two observations:

(1) The tip of the pin (were I showed cracks) is ~1mm larger in diameter.

(2) The pin itself is not fixed like my original. It slides up/down about a half mm and it's free to rotate.

Presumably these things are OK and are just design changes??

BK

On further examination I now see a third difference. The old servo has a spring under the rod (hidden) that seems to take a good percentage of my body weight to compress. The new servo has no spring at all under the rod, which explains its ability to rotate and move up/down just a little. Hmmm.

[BrooklynBay]

Could you post a side by side comparison photo of both servos?

[BK_89iX]

Originally Posted by BrooklynBay

Could you post a side by side comparison photo of both servos?

Sure thing. See below.

BK

[BrooklynBay]

Thanks for posting the photos. How much did they charge for it? It looks like they shipped it pretty quickly. It's OEM Ford too.

[BK_89iX]

Originally Posted by BrooklynBay

Thanks for posting the photos. How much did they charge for it? It looks like they shipped it pretty quickly. It's OEM Ford too.

Tousley had it in stock and shipped same day - love those guys! Part was $33.24. Decided to go new instead of used. BTW, it came with O-rings, but I already removed them to make way for D-rings.

My initial concern was that it was missing a spring for whatever reason, but it seems instead to be a revised design. The total length of the rod is identical for both parts, but the new one seems to be secured differently (notice the depth of the center "washer" piece). I don't think the rods themselves would therefore be interchangeable, assuming I could manage to get that tiny bottom clip off near the cast Ford logo. Hopefully the lack of that very stiff spring action in the early assembly is not an issue for me.

BK

[BK_89iX]

Installed this today with viton D-rings and it went smoothly.

The day before, I put the servo assembly into a ziplock bag and stashed it in the freezer. Popped the cold unit right into the tranny with no drama/force whatsoever. That cooling trick is really fantastic, BB.

BK

[CDW6212R]

Good idea, another reason to have a spare refrigerator in the garage. Check!