Won't shift into high gear - 1996 Chrysler Town & Country

This may be a faulty transmission control solenoid. As you know, automatic transmissions use pressurized hydraulic fluid to change gears. ... When this is faulty or not working properly, this can cause a delay in gear shifting or in some cases cause the car to not shift at all.

https://www.yourmechanic.com/question/my-car-won-t-shift-gears-and-revs-really-high-by-vilma

clutch spring

see if this link helps you out.... My 2004 chevy trailblazer won shift from second to third gear Google Search

the govenor is set too high

Change the trans solenoid pack inside the transmission pan

One part--- contains 3 pressure solenoids & all 4 shift solenoids

are there any codes? Does it shift ok in 1st and 2nd? sounds like your over drive shift solenoid or your 3 and 4 shift solenoid is stuck and needs to be replaced

May check fluid level and if low would more than likely indicate a leak. could also be a sensor that controls the shifting. does check engine light come on and if so,this could indicate a bad sensor.

It might work short term, but it sounds like the overdrive might almost be out of your truck.

transmission sencor

I would service the transmission before assuming anything is wrong or broke have it flushed and have a new filter and fluid put in.. Then go from there.