4Lo works, 4hi doesn't, help please

rommel05 · September 3, 2017

Hello, I have an 06 Silverado 1500 Z71, and I'm having an issue with 4WD. It has the manual tcase floor shift. When in 4hi, the light on dash doesn't come on and 4wd doesn't work, when in 4lo, everything works fine including light on dash. Occasionally while driving in 2hi, when I come to a stop, the 4wd indicator light will come on until I take off again, which I'm guessing is just telling me I have an issue. I don't believe it's the actuator since 4lo works, so I'm guessing there's some type of switch attached to the floor shifter that isn't sending a signal to the actuator when in 4hi. If you have any thoughts, please share! Thanks, Ryan

Supreme Pizza · September 3, 2017

Could be a switch / sensor or something somewhere on the t-case. Couldn't hurt to replace the t-case fluid or at least check the fluid level. I'm not a 4x4 expert by any means. Did you try Googling the symptoms? What do you use the 4x4 anyway? Playing? Working?

rommel05 · September 4, 2017

Yes I believe it's a switch/sensor but I need help finding what sensors are on the tcase. I've been researching heavily and it's hard to find information on manual shift tcases. Yes, changing the fluid wouldn't hurt but shouldn't be the cause to my issue as 4lo works. I just use it for snow once or twice a year so not too important but is nice to have when needed and not have to drive 10mph.

Supreme Pizza · September 4, 2017

Are you sure that the font end is not locking in? Did you try putting it in 4H, and then spin the tires in the mud or snow? Do the front tires spin? Might be able to put the front actuator on a toggle switch. If you try that, make sure you use a circuit that only has power when the ignition is on. Also, only hit the switch under the correct circumstances, what ever those might be. You may be able to call the dealership parts department and explain that the sensor is bad, and ask them to look it up on their exploded view parts diagram.

rommel05 · September 10, 2017

Are you sure that the font end is not locking in? Did you try putting it in 4H, and then spin the tires in the mud or snow? Do the front tires spin? Might be able to put the front actuator on a toggle switch. If you try that, make sure you use a circuit that only has power when the ignition is on. Also, only hit the switch under the correct circumstances, what ever those might be. You may be able to call the dealership parts department and explain that the sensor is bad, and ask them to look it up on their exploded view parts diagram.

I checked if it was in 4WD by turning really sharp on pavement which didn't show any binding. I ended up ordering SW3829 transfer case switch for NVG 261-NP2 transfer case which is located on top of the tcase right next to the gear lever on the driver side. Replaced it today and everything works great. The switch sends a signal to the dash light which then sends a signal to the actuator, and the old switch wasn't sending the signal. My dash lights up now and 4WD works. Hope this helps someone else with the same manual transfer case because it took a lot of researching to find the right switch, which was a mere $30 at autozone. I ended up having to take a vent tube loose so I could turn the plastic vent in order to get a 1-1/6" deep well socket on the switch. The back of the plastic vent was almost touching the nut on the switch. Thanks for your suggestions, so happy I fixed it!!!

Derek406 · February 3

Mine was doing the same exact thing and I was assuming it was the switch so I guess I’ll try it and see what happens. Thanks for the help! This was the only bit of information or similar issue that I’m having so I found this exceptionally useful.

ALAN HOLLENSBE · February 6

2005 gmc 2500, 4x4 selector switch comes on randomly, 2wd, N, or not at all. I can drive normal in2wd. It will put itself in 4wdL and you can't get it out and you can't drive it like that. Leave it off 10 or 15 minutes and it will choose a different mode. Changed the switch, didn't change anything.