My 94 aerostar deosn't engage into Drive , reverse or any gear when the engine is cold. Should I repalce the Tranny now? Could a vacuum tube cause this or a bad filter? Fluid fine smells and looks good- level fine - and there is no slipping or hesitation once the engine is warm. I am completely lost.

 

There are reports of this occuring on older vans, being especially prevalent when parked on a grade. Also, these transmission are exquistely sensitive to improper fluid levels. Might try adding an additional half-pint of fluid to see if this corrects the problem.

Other sources would recommend adding a can of transmission flush first, driving an hour then performing a fluid/filter change. This assumes the internal valves are sticking and the flush removes deposits and restores functionality. Some swear by it but personally, I have no direct experience with this method.