I have a 89 RS V-6 4 speed auto 94K. Transmission had a machine flush at 65K. Last Sunday, replaced the pan gasket (leaking), and filter. The pan was clean, very little residue. Added a bottle of Lucas, then topped it off with Valvoline Max Life fluid. The car shifted great for three days, then when it got hot, lost 3rd and OD, one-two still shifts fine. When the vehicle cools off, 3rd and OD come back. Did a full machine service the other day, but to no avail. Any ideas? The "experts" say its the 3-4 clutch pack, but why does it shift fine when its cold? Thanks!