92 240 auto transmission up date

[240Mech]

Ok 2 times this happen to me. Stock transmission w/ huge chevy 3500 series transmission cooler on the front of car. bypass the rad. My transmission blows up at speeds of 80 mph while on highway. I was told by a great transmission builder that the transmission had a poor check vavle going into rear of the transmission, Rear cooling line. Inside the tailshaft. Iam going to call 2morrow., But has anyone ever heard of this or done this type of upgrade on thier 240 auto transmission. It sounds right to me. Because 2 times on the hyw the transmission came apart the same way. At speeds of 80 mph. Now iam going to rebuild the transmission. I would like to know if anyone has heard of this or has done it.Thanks Brian's Auto in fla.