4x4 drive issues

MADD*MAX

Member
Sep 23, 2012
46
0
6
Alberta
Ive been trying to diagnose a 4x4 problem for sometime now. My truck likes to but itself self into 4Lo all the time all on its on but does not put any power to the front wheels. It definitely gears down though because its sifts very rough. I ceased my front diff from it always shifting into 4x4 drive as it pleases. I have replaced the front diff and i know she was ceased good beacuse you cannot even turn the yoke by hand. Now i have power to the front wheels in 4hi but when i put it in 4lo i still have no power to the front wheels and it often gets stuck in 4lo. I replaced the push button switch so i know that was no the issue. I do often get a service 4wd drive message but have no scanner to check the codes. I drained the t-case oil and found no fillings and it was very clean. Could it be my tansfer case control module causing all this or is the something wrong internally in the t-case. Also lots of times the light goes out on the switch or I try to swicth in and out of 4wd and it just flashes but does not engage.
 

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
2,368
1
38
Berthoud, CO
If your getting a 'Service 4x4' light then there will be a code stored in the transfer case control module. Find a Tech II or pay a shop to pull the code for you. That'll help you and us out a lot and will be cheaper than throwing parts at it.
 

MADD*MAX

Member
Sep 23, 2012
46
0
6
Alberta
Ok well ill start off buy saying i had a good experience at the dealer today. I randomly stopped in with my duramax to see if they could take the 5 minutes it takes to scan it with the tech 2 and to my amazement they did no problem. Also they never even charged me for it. Anyways this is the code P1875. Shows up as 4x4 switch circuit error or something along those lines. The tech told me its likely just the switch. The thing that gets me is i just changed the switch cuz that was my feeling all along. I got the switch from a wrecker though so theres a very small chance it was bad two but unlikely. Does anybody have any thoughts on what else it may be?
 

mackthehack

DUH...
Apr 16, 2007
831
0
16
Do you have this posted on df?

Possible bad switch from the junk yard. A short in the harness or bad pin/connector. Possible actuator at the diff or on the tcase.

If you know someone with a similar truck that is 4wd. The 4wd does work on that truck. Try swapping switches just to verify that is the cause of the problem.