5R55S reverse servo has a pin hole in it

[RImike]

New to the forum, been lurking for a while and trying to sort out my problem and I see this hasn't been brought up yet.

04 Explorer XLT with the problematic slamming in reverse. When cold, it doesn't happen, however once warm there is the delay, then slam.

I took the reverse servo out to inspect the band and clean out the internals of the housing. Upon inspection, I found a tiny pinhole in the servo top.

Can anyone put their hands on a new one and verify that there isn't a hole in it? It's tiny and the only way I found it was that I filled the cup with fluid, inserted the servo, and air tested it and it was bubbling fluid through it.

 

[transman304]

Are you talking about the piston with molded on lip seals? I don't recall ever seeing a hole. I will check tomorrow and let you know

 

[RImike]

Are you talking about the piston with molded on lip seals? I don't recall ever seeing a hole. I will check tomorrow and let you know

Yes, the reverse servo piston.

Thank You for checking

 

[transman304]

I didn't have a new one on the shelf. I will check a core on Monday and report back.

 

[JK080]

I had one on the shelf and I dont see any hole in the piston.

 

[transman304]

I am with James as the servo I found did not have a hole. Can you post a picture of the piston you have?

 

[RImike]

I'll do you one better and post a video, while it renders to YouTube here is a picture holding it up to a light:

 

[RImike]

Here is a YouTube Video I made:
https://www.youtube.com/watch?v=_rG2NWgtkbg

 

[transman304]

I can see it. Thanks for the video,i will clean up my core part and double check. It has me curious.

 

[RImike]

I didn't catch it until I was going to re-install it and primed the servo and noticed it leaking out the top. It's such a small hole that it's easy to not catch.

The interesting thing is that it slams into reverse only when warm, not cold. I wonder if when it's cold, the fluid is thicker and the metal hasn't heated up and expanded just enough to overcome the fluid loss vs when its up to temp.

 

[JK080]

Yep I held the one I have up to the light and mine also has a small hole, this is not uncommon to have bleed holes, I guess its there to bleed any air out that might get behind it.

 

[transman304]

Learned something new today. I now know that the servo piston has a SMALL hole in the top. Maybe .020" Had to really look to find it.

 

[RImike]

Back to square one.

I don't want to pull the valve body, but I suspect that the reverse engagement valve might be at fault next.

 

[RImike]

Update:
After sitting for about 2 weeks with the reverse servo housing and the solenoid block assembly removed, another 1 quart of fluid drained.

I put the solenoid body in the ultrasonic cleaner and I was quite supprised the amount of gunk that came out.

I put everything back together with a new filter and about 8 or so quarts of fluid (put 8 in, some leaked out while setting the proper level). I also disconnected the battery and put a jumper between the leads to reset the computer.

After test driving and getting everything up to temp, what was a delayed then harsh engagement is now an instant engagement. However I now notice there is a 2 second delay, yet smooth going into forward and I honestly can't remember if it was there before or not because I was so distracted with the reverse issue.

 

[transman304]

Thanks for the update. I have never had any luck with putting electronic parts in the ultrasonic cleaner. You are correct about all the junk that the hold. I wish you luck. I feels good to do a repair and have a positive result. Great job!