My brother owns a couple of AAMCO Transmission stores, " Heat and Friction " cause Tranny fluid to go brown. He said it may have been a bad build? a couple of galleries may have been blocked because they may not have a cooker to completely bake the old clutch out of the casing prior to rebuild. " I would certainly ask if they have one" either way she was slipping the whole time you towed by the sound of it? It sounds like your getting hosed?
My 02
thewelshm
Man, an aamco stole mygirlfriends GPS out of her car