I have a 99 ford van that runs well and drivable but only for about 3 minutes. The transmission will not engage after that. If I let it cool for about 1/2 hour it will get up and go again but only for 3 minutes like before. Fluid is ok. I did a stall test within that 3 minutes and it seems normal. Where do I go from here?

Mikel Cobb
Educator/Instructor
Ladysmith High School Auto Dept
Ladysmith, Wisconsin, USA