I Have A 1989 F250 That When Running Cold Shifted Perfectly But After Running Down The Road For A Good Half Hour Would All Of A Sudden Drop Out Of Gear And Go In To First With No Engine Braking And Stay In First. No Shift Into Second Unless I Manually Shifted Into Second, But Then No 3 Or Overdrive Because I Was In Second Manually. So At Start Up In Drive I Would Stay In First With No Engine Braking And No Upshift, But Only When Hot. I Took To Local Transmission Shop Who Talked Me Into A Rebuild, Got The Truck Back Ran Fine For 300 Miles Then All Of A Sudden Same Exact Problem. The Computer Has Recently Been Replaced Because Someone Broke In And Stole It, So It Is Not A Computer Problem, It Had The Same Problem With The Old Computer As Well As With The New Computer. New Solenoid Pack With Rebuild So Not The Solenoid Pack. Does Someone Have Any Idea What Could Be Causing This Problem. Tranny Shop Says Not The Tranny So They Want Me To Approve Many Hours To Go Through Electrical System.