Original pressure test showed 90 psi forward, 200psi reverse, which to me indicated bad piston seals. rebuilt transmission but never could find any thing obvious causing low pressure, thinking the problem was in the control valve possibly i installed trans and installed a different control valve. yesterday i rechecked pressures but i connected the gauges while the truck was cold, both clutch packs 200psi but as the truck warms up the forward pressure gradually drops to 90psi when up to operating temp. im thinking possibly a cracked piston or something. one of the local dealers rebuilt three of these transmissions for this customer about a year ago, replaced pumps, control valves and converters and never could get them to last more than a few months before they would start slipping again