Well,I tried searching high and low on multiple sites,but can't seem to find how to check the electronic shift on the fly switch in the interior,then were else to look for.Is there a thread somewhere someone could point me to ?I did install a new transmission electronic shift motor,but no luck. I imagine the 4x4 process starts at the interior switch.The 4x4 did work once or twice when I first bought the truck,but I did'nt use it cause when in 4x4H the tires I had were at different wear ponts and beat tires,which I thought was causing the 4 wheel drive to sound like it should not.Can I pull the elec.shift motor and manually put it in 4wd successfully to test the 4wd system now that the tires are new.

 

Here is an overview of the operation.
The dash switch signals the GEM module to run the transfer case motor to it's first position.
This turns a shaft in the transfer case and an electric cluch to engage the gear train and signals a solenoid vacuum valve on the firewall to pass engine vecuum to the front axle actuator to engage the front drive axles.
When this sequence completes, the light on the dash is lighted by the GEM module.
It's a loop action such that your switch does not light the lamp ditrectly.
Electrically there are fuses, harness and relays involved plus hardware points.
Good luck.

 

The most common issue with that system is an interuption of the vacuum supp;y to the solenoids. If battey acid spills on themthere done and they are of course right next to the battery. Start off checking them for leasks..

 

Thanks for the reply guys.I'll start by pulling the electric shift motor and then putting it in 4wd,then checking to see if the shift motor changed position.The firewall 2wd/4wd actuators do have vaccum to them,but always stays passing vaccum through the 2wd actuator,and I don't get any lights on the switch inside.I puled the 30 amp fuse to the 4wd system,cause occasionally the shift motor{ which is new} would drive inbetween 2wd/4wd and stop - the trans would'nt engage drive like in neutral till you manually took shift motor off,and manually turned the lever back to 2wd on the trans.

 

The circuit board on the case motor controls the firewall solenoids by it's rotation.
In the first position the solenoids are operated the same for both High and Low usage. (locks up the front same for both)
The differences in the second positon are the transfer case gear train is changed for 4L and a signal is sent to the PCM to change the Low range shift points in software.
The other difference not related, is the GEM looks for the trans to be in neutral, foot on brake and vehichle not moveing more than a very small movement all at the same time..
Good luck.