1st post on here.

O.K. heres whats happening. My dash mounted switch is flashing on the 4Hi setting. It will switch to 2hi and the light stays on solid, I can also hear the switch over. When I switch back i hear it but the light just keeps flashing. When I switch to 4Lo it goes on solid and the 4Hi stays on flashing. But upon going around the block a couple times to see if it would engage I noticed the 4Lo would switch off, and go back to 4Hi flashing. It seems to switch itself as soon as I get past 1st gear. I have read some of the older posts similar to my problem with no help. I have also replaced the dash mount switch, but it still the same. Now about me, lol, I am an auto idiot so please keep any explanations as simple as possible. I have some mechanics in my family but I am tired of burdening them with this truck. Mabye with some of your guidence and wisdom I could get thru this. Thanks in advance. Don

Hi Don and welcome to AF. The most likely cause of your problem is the encoder motor on the t-case. The flashing light in the button is saying that the encoder motor is not going to the commanded position, or, it's going to the commanded position but the internal switches are not sensing that.

This motor is what actually changes the t-case into the different ranges (4hi-4lo-2hi). When you push one of the dash buttons it sends a signal to the TCCM (t-case control module) which sends a signal to the motor to change ranges. When the motor gets to the selected position the internal switches send a "feedback" signal to the TCCM and the selected push button light comes on steady.

A scan tool capable of getting into the t-case control system is needed to properly diagnose your problem.