98LS1driver

iTrader: (2)

Went to install a aluminum piston in mine to replace the plastic one but I noticed that the one I got came with another shaft but it's bigger in diameter and won't fit into the accumulator housing. What do I need to do?

mrvedit

The 4th accumulator piston has the larger diameter shaft. Any local trans shop should have the right one for you; they are only $3 or so.

If you decide to order one:
http://www.transmissionpartsusa.com/...-000035957.htm

Some models/years of the 4L60 (or perhaps 700R4) did use the larger shaft diameter for the 2nd accumulator piston, but most use the smaller shaft diameter.

Alternatively, you can get the Sonnax pinless accumulator piston which will work as either a 2nd or 4th:
http://www.transmissionpartsusa.com/...-07799803k.htm

I've heard of the springs breaking too, so you might want to replace the spring(s).