99 GMC sierra 4wd high wont engage

[misfitmp]

I have a 99 GMC sierra 1500 V6 4.3 and I can't seem to get the 4 wheel high to work my 4 wheel low engages and works great but the high just wont work I have a floor shifter not the push button on the dash and the shift lever goes into position and the front drive shaft turns just doesnt lock the front wheels anyone have any ideas thank you

[gmtech4]

I have a 99 GMC sierra 1500 V6 4.3 and I can't seem to get the 4 wheel high to work my 4 wheel low engages and works great but the high just wont work I have a floor shifter not the push button on the dash and the shift lever goes into position and the front drive shaft turns just doesnt lock the front wheels anyone have any ideas thank you

Donkey dink actuator OR the power from the tcase switch ,

 

You need a service manual to self diagnose this

[misfitmp]

Thanks for the input when I get under the truck and mess around with the linkage I can get the motor or the actuator not sure what it is but it makes like a whiring noise kicks on but I adjusted the linkage as much as I could and still seems to be loose not sure if there is some kind of electrical contact on the tcase houseing or if its really just the sloppy plastic ball clips cant be too sure untill its a bit warmer out this'll do for now thanks

[gmtech4]

Thanks for the input when I get under the truck and mess around with the linkage I can get the motor or the actuator not sure what it is but it makes like a whiring noise kicks on but I adjusted the linkage as much as I could and still seems to be loose not sure if there is some kind of electrical contact on the tcase houseing or if its really just the sloppy plastic ball clips cant be too sure untill its a bit warmer out this'll do for now thanks

Mechanical t cases are easy , the shifter shaft closes a switch that insentually tell the donkey dink to apply the front diff shift collar ,

 

Get a schematic .... Alldata.com $27/ yr , no brainer imo