GMC Troubleshooting Questions? Ask a Mechanic for Answers
My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.My info is somewhat limited on your model here but I had seen no one else has responded and would like to see if I can help here.If at any time you feel that I cannot help with this please let me know.
If the transfer case is engaging but the front differential is not this can be a fault with the shift fork inside the front differential damaged or the gear damaged inside of it causing no engagement and if this is an electronic engaged front differential the actuator can fail in the front differential and cause this issue here as well.This will have to be inspected/tested further to pinpoint the cause for this fault here and then from there it can be repaired.This may require a scan tool plugged into your vehicle that can communicate with all computers to check the actuator as well as electrical test equipment to test it.If the electrical part of the 4wd is operating properly then the front differential may have to be removed and inspected internally for any mechanical faults needing repaired or replaced.
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Can you tell me the year of this model here and I can see what I can locate?
O.k.,this front differential should have an electronic shift actuator and it is usually located on the passenger side of the front differential.I done show the exact specifics on this model here for this but it should use an electronic actuator that engages when shifted into 4wd.This can fail in some cases needing replaced but it is also possible that the internal shift fork or gear in the front differential is broken or damaged needing replaced.If you can locate the actuator on most models it can be removed then the vehicle shifted to 4wd to see if it extends for 4wd and retracts when in 2wd.If it does then the actuator is o.k. and the front differential needs inspected further to locate and repair the fault internally.
Let me know if you need anything else and feel free to rate my help here.
It usually looks similar to this here and threads into the front differential housing and has a large connector attached to it.
O.k.,let me know what you find here and if the actuator isnt located let me know.
O.k.,this model does not use an electronic actuator then.The front wheels may be locked in at all times in the differential mechanically and when the transfer case is shifted into 4wd then the 4wd operates from there.If there are no actuators on the differential and your front drive shaft is engaged and spinning in 4wd this indicates an internal mechanical fault in the differential.
Check and make sure your front hubs are not manual locking hubs.This was an older set up to where you would twist the hubs at the wheel area to lock the front differential.If it does then try and manual engage them and see if they work from there.If they do not or they are locked in then the fault is in the differential and needs removed and inspected for repair.
O.k.,Let me know when your ready.
Yeah some of these have the old style manual hubs it all depends on how it was built.
I dont recommend leaving them locked in 2wd on dry road surface as this can cause damage to the front differential but on a slippery surface you may be o.k.It is best though to only shift these in when you need 4wd to prevent wear.