I have a 1993 Ford E250 Van. My trans shifts good in 1st&2nd gear.Sometimes it will not shift to 3rd gear.I have to push the overdrive button in and out several times to make it shift.It feels as if theres a valve or solenoid not working properly.Also I can accelerate to 45 to 50 mph,let off the gas and it will shift on its own,but this is hard on an engine with 365,000 original miles. Any help would be welcome,Thanks Guys