'85 Riviera Convertible - Wife has had it for years, and I'm trying to get it going to sell. Tons of white smoke, low transmission fluid, weird shifts, so, I suspect the modulator valve diaphragm has ruptured. Problem is, I have no experience with these cars, and I cannot seem to find the modulator valve. It would be a piece of cake to replace on a standard RWD TH xmission, but where the heck is it on the TH 325-4L ATSG?! Any help would be appreciated. TIA.