Can I reuse my 2nd accumulator piston?

Yes, but only if it is steel and the rubber seals are soft and undamaged, including the cover. Do not reuse pistons with hard or damaged seals.

What is the part number for the steel 2nd accumulator replacement piston?

P/N F7AZ-7F251-AA, which fits 1992-2010.

Should I keep an aluminum 2nd accumulator piston?

No. The aluminum 2nd accumulator is not recommended due to a high failure rate on seals; replace it with a steel piston.

What should I do about an aluminum 3rd accumulator piston?

It's better to upgrade to the steel type, Ford #F7AZ-7H292-AB, and save the aluminum one for AODs.

What if the 4th band pin bore is worn?

A worn bore causes a big forward clutch leak. A repair kit is available at www.servobore.com or by calling 715-458-2617 (FAX 715-458-2611).

When is the new spacer needed on the 3rd retainer?

If the point of the 3rd retainer directly touches the valve body separator plate, install the new spacer, using assembly gel to stick it to the retainer.

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Ford E4OD/4R100 2nd & 3rd Accumulator Install - TransGo Shift Kit Page 3

Step-by-step transmission 2nd accumulator rebuild instructions with part figures

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Service procedure for the 4th-band/2nd accumulator showing spring and piston replacement steps with labeled figures and warnings.

AI caption January 2019 · Photo 199 of 343

This is page 3 of a TransGo transmission shift kit installation instruction sheet (dated 05 Aug 2013, © TransGo 2013) covering the 2nd and 3rd accumulator pistons in a Ford automatic transmission case. Step 1 covers the 2nd accumulator, which requires a steel piston: old parts are removed, and the steel piston and cover may be reused only if the rubber seals are soft and undamaged. New inner and outer orange springs are installed into the small end of the piston, the case bore is lubed with ATF, and new purple inner/outer springs plus a solid spacer are placed onto the cover before installation, holding pressure until the snap-ring is reinstalled. An aluminum 2nd accumulator is not recommended due to high seal failure rates; the steel replacement piston fits 1992-2010 and is P/N F7AZ-7F251-AA. For the 3rd accumulator, upgrading aluminum pistons to steel (Ford #F7AZ-7H292-AB) is advised. Step 3 installs a new white spring; Step 4 adds a new spacer if the 3rd retainer point directly touches the valve body separator plate. A warning covers the 4th band pin bore: a worn bore causes a big forward clutch leak, with a repair kit available at www.servobore.com (715-458-2617). A labeled case photo identifies the EPC solenoid, 4th, and LR locations.

This document covers 1992-2010, which may differ from this 1990 Ford F-250.

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Frequently asked questions

Can I reuse my 2nd accumulator piston?: Yes, but only if it is steel and the rubber seals are soft and undamaged, including the cover. Do not reuse pistons with hard or damaged seals.
What is the part number for the steel 2nd accumulator replacement piston?: P/N F7AZ-7F251-AA, which fits 1992-2010.
Should I keep an aluminum 2nd accumulator piston?: No. The aluminum 2nd accumulator is not recommended due to a high failure rate on seals; replace it with a steel piston.
What should I do about an aluminum 3rd accumulator piston?: It's better to upgrade to the steel type, Ford #F7AZ-7H292-AB, and save the aluminum one for AODs.
What if the 4th band pin bore is worn?: A worn bore causes a big forward clutch leak. A repair kit is available at www.servobore.com or by calling 715-458-2617 (FAX 715-458-2611).
When is the new spacer needed on the 3rd retainer?: If the point of the 3rd retainer directly touches the valve body separator plate, install the new spacer, using assembly gel to stick it to the retainer.