If you do have water in the fluid, the lucas slip stop will just help destroy the transmission while you drive it to see if it has effect.
You 'really' need to do your own visual on the fluid. It's easy, just pull the dipstick out and see what the stuff looks like. If it is brown and smells like burnt toast, you are in for a rebuild. If it's foamy and clear it's too full and the foam will kill the unit because air bubbles don't lubricate. If it looks like a milkshake it has water and needs to be drained and replaced. Twice likely to get all the water out.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: N>