Tranny guys help me. Thanks

[rafterman191]

Last night, my "new" 85 C10 long bed 305 ci, 350 tranny lost it. With no warning (to me at least) the transmission went. To get it to move, you can rev up the engine and get maybe 5 mph out of it on flat ground. When it went to shift last night, I heard and felt it slip, and then nothing. Checked the tranny fluid this morn and it's like gray soup. Anything I can do to isolate a problem or does it sound like tran failure? Keep in mind, there has been so prior slipping in the tranny. Could new tran fluid and filter bring her back? thanks for any help.

eta. removed the tranny pan. Fluid is more solid black than grey. Seems pretty gummy.