My 1986/1987 Itasca Micro Mini Motorhome with 22RE engine has automatic transmission which will not shift into overdrive.
Button on steering column doesn't seem to make any difference (no click noise, change in driving conditions and no dash light comes on when pushed).
A trans shop put it onto hoist and said overdrive worked when they put power to it (solenoid) directly, but didn't want the hassle of figuring out what it needed to fix the problem.
Any tips appreciated!

 

Get yourself a multimeter.
Check the switch works.
Check the switch signal reaches the transmission controller.

Fire your transmission guy for being lazy..