TH 400 problem part name?

I'm trying to id this part. It's from a th400 out of a 4x4 that a friend is rebuilding. He said its from his reverse manual pattern valve body area, and came across it cracked. Its like a plastic cup that holds a spring over the piston in the valve body. Does anybody know the name? Part #?

http://www.rockymountainextreme.com/attachment.php?attachmentid=26404&stc=1&thumb=1&d=1177125997 (http://www.rockymountainextreme.com/attachment.php?attachmentid=26404&d=1177125997) http://www.rockymountainextreme.com/attachment.php?attachmentid=26405&stc=1&thumb=1&d=1177126030 (http://www.rockymountainextreme.com/attachment.php?attachmentid=26405&d=1177126030)

Thanks,

Scott

Can't access the pics on that site.

Your dealer should have it or a transmission parts place or transmission repair shop.
If you re reffering to the piston in the valve body.
Ask for a front accumulator piston some are aluminum.

Thanks guy's that helped!