Blown overdrive servo piston | Ford Explorer Forums - Serious Explorations

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Blown overdrive servo piston


November 7, 2012
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City, State
Williamsburg VA
Year, Model & Trim Level
2003 Explorer XLT 2WD
I'v been diagnosing a PO775 code in my new to me 03 explorer, 2WD, 5R55S.
Solenoid block tested good and I believe it to be a replacement since it is a bosch piece not ford.

Adjusted the bands and they torqued up so they're not broke. So I pulled the servo covers and I have a busted overdrive servo piston. The center is completely broke out.

Servo bores seemed fairly tight (154k) with the overdrive bore tighter than the intermediate.

I re-installed the intermediate piston and slid the pin from the overdrive piston back in to keep the strut in place.

So my question is, Is the broken piston the problem or the result of some other problem? If I replace the piston is it likely to blow out again? Thanks

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I have seen just the piston itself break like that and the servo bore not so worn.

That kind of mileage there has to be some decent amount of wear to the bores.

I would just replace the piston and if it works like it should I would let it ride until another issue. Either way the piston needs to be replaced.

How tight should the bores be? The intermediate piston slid in pretty easy. I tried to wiggle it in the bore and I couldn't feel much slop.

The overdrive piston was tighter in the bore.
Both bores still looked round to my eye, but?

I couldn't imagine trying to fit the modified O ringed servos into either of the bores.

I'm assuming this is the original tranny as nothing appeared to have been apart before, aside from filter change and newer solenoid block.

I'm going to throw another piston in it and see how it holds up.

Brooklyn, How well do the modified servos work? Have you used them? Any idea of the life expectancy? I see they come with "replacement o rings. I surely don't want to be dropping the Y pipe and tranny crossmember every 10k.

I don't think I could get an o ringed servo piston in the overdrive bore. The intermediate? Maybe?

My plan for now is to replace the blown piston with a stock one and run it and see what happens.

I don't want to drop $200 bucks on something that may work with no guarantee.
I have no real drive time on this Explorer. So no idea of slippage or other problems.