88 auto trans swap

[Thomas J. Donohue, Jr.]

Hi...#3 child, #2 son is in the middle of a swap of a '90+/- 100 autobox
into his '89 90 autobox that ate itself.  He is concerned about what
fluids would be the best to install after the mechanical swap is done.
I don't do autoboxes and thus have no clue.  Does anyone?  Help is
needed soon because the components are being switched as I write and he
is hoping to get the beast back on the road by this weekend.  Any BTDT
would be greatly appreciated.  Regards.  T.  P.S.  Any different gear
ratios that he should know about?