Hello All,
Throwing out a question on my issue with the 4wd on a Chevy 2003 2500HD with the 8.1/Allison and a NP 263 transfer case. It will not go into 4wd, 3 button panel, no auto. Push 4H and it flashes with the 2H and then puts "service 4wd" on dash. So...I thought I did not hear t-case motor, so I did replace that. it went well. When that did not work, I changed the front differential motor, that did not do it either. I saw a note on cleaning the ground wires under the frame, and they were not good, (Minnesota salt), that did not seem to change anything either. I thing I can hear both motors when you hit 4wd. I can hit 4wL and get low range. I tied a zip tie to the front driveshaft and it flaps when I drive in 4wd. Driveway is all snow and I can tell 4wd is not engaged. When inside and motor off, I can hear both motors when I hit 4wd. So It was late and had to walk away from it. I hope I explained the issue well enough and that maybe someone has some direction for me to look. Anyway, thanks and take care from TF MN. Brad

 

Problem is fixed!
It ended up being the ground wires down under the door. I did clean them and nothing changed. But then I cut the terminals off and cleaned up the badly oxidized copper and soldered new terminals on. I used new bolts and star washers and ground down to bare metal. Coated it with a spray and it all worked!
Thanks! Take care.