Q: Truck isn't engaging into 4 Hi, but will go into 4 Low.

asked by on January 13, 2017

I have a 2003 Chevy Silverado 2500hd 6.6L Duramax. I just got the drivers side CV axil halfshaft repaired by a repair shop yesterday, and now today the truck will not engage into 4wd Hi. It will engage into 4wd Lo however. When I try to engage to from 2wd to 4Hi, it sounds like it's trying but it won't actually engage. Is there any idea what could be wrong? I took it back to the shop, and told them that the transfer case was working fine before I brought it to them but they are basically denying ever even touching the transfer case even though they told me they test drive the truck in 4wd after replacing the CV Halfshaft.

My car has 200000 miles.
My car has an automatic transmission.

Hi there. Sounds like the shifter module motor or shifter rail is not working properly. Check the wiring on the shifter module motor on the transfer case and see if the wires are split or damaged. If the wires are good and the harness has no corrosion or oil in it, then remove the shifter module motor and put it on a jack or something while it is hooked up under the vehicle. Jack up the vehicle and put the tires off the ground and put the vehicle on jack stands. Start the engine and put the vehicle in 4 Low and observe what the shifter module motor does. If the motor rotates and is working, then the issue lies within the transfer case. If the motor only turns a little and mostly turns on 4 HI, then I recommend replacing the shifter module motor to the transfer case. Also, the transfer case lock switch may also cause the transfer case to not engage into 4 HI as well. I recommend seeking out a professional, such as one from Your Mechanic, to help you diagnose the transfer case before replacing any parts.

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