I'm trying to help out my son-in-law on his 1990 F-150 2WD, 302 with E40D trans. It shifts fine when it's cold but the warmer it gets, the more it refuses to shift 1st to 2nd. The problem may have started when a cooling line came apart and he lost most of the fluid. He didn't drive it far so I don't think it overheated badly. We fixed the line and replaced the fluid, and it seemed to be fine, but started acting up a few months later. I'm thinking the cooling line may be blocked and the fluid is getting too hot? Any ideas would be appreciated.