OD on/off button does not work
 

Shortly after I bought this truck used, the OD button on the shift lever quit working. It used to light up a light on the dash; that no longer happens. It does shift into OD but it will not lockout OD when the button is pushed.

Any ideas on where to start diagnosing this? Thx !

96k miles

Here's a possibility:
There are 2 thin black wires that pass through the tubular shifter from the O/D Cancel switch. As they exit the hollow shifter, they make a 90 degree turn before traveling down the top of the steering column. At higher miles, it is fairly common for those wires to chafe and/or break from repeated shifter movement. Check fuse #6 in the dash box and remove the top column trim to inspect the wires.

question
 

How do you get into the handle to replace the switch / button?