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FIXITMAN, Master Technician
Category: GM
Satisfied Customers: 17475
Experience:  ASE Master Certified
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I have a 2004 hummer h2 that appears to be stuck in 4 lock.

Customer Question

I have a 2004 hummer h2 that appears to be stuck in 4 HI lock. The light shows 4 HI though but not 4 HI lock. Does this trigger to change the light come from the actuator or a sensor somewhere on the diff? I'm really trying to figure out if the diff is bad or maybe just a bad actuator. Any thoughts?
JA: Just to clarify, what are the exact lights you're talking about?
Customer: The 4WD status lights on the center console
JA: Are you fixing your H2 yourself? What have you tried so far?
Customer: Simple diagnosis. Obvious - check fluids. Both tcase and front diff were low and they both have 180K on them so the fluid is not exactly clean. There was a bit of smoke coming from the transfer case plug though when I opened it. I don't hear a click when I try to switch between 4 HI lock and 4 HI which made me think it may be the actuator. The front wheels are definitely locked together though as if it's in 4 HI lock.
JA: Anything else you want the mechanic to know before I connect you?
Customer: I was driving this weekend and hears a screech upon decelleration - like the kind that sounds like a dremel. Aside from that it runs just fine. Drives straight, turns terribly like the wheels are locked.
Submitted: 1 month ago.
Category: GM
Expert:  FIXITMAN replied 1 month ago.

Hello my name is Bobby. Can you tell me if there is any check engine light or any other warning lights?

Customer: replied 1 month ago.
The funny thing is there is a check engine light that came on starting yesterday but no code. The scan tool doesn't pick up anything. The problem started on Saturday and the light came on on Monday. I drove it on the expressway at about 85 mph (usually we only hit the 65 mph roads) for 45 minutes - all of the gauges were good but my fear is that if the fluids were old it may have damaged something. It still drives and shifts fine in a straight line. But on the turn the front wheels are locked as if in 4 HI locked.
Customer: replied 1 month ago.
I wonder, could the brakes play a role here? what makes me wonder about this is that while I'm driving if I switch into for high lock I can feel the front differential engaging. When I switch it back to four high with no luck I feel it disengage. I noticed the binding when I'm turning. Could there be something in a turning motion that would be mechanical in the differential and forcing it to go into lock or my just be a break issue?
Expert:  FIXITMAN replied 29 days ago.

Thanks for getting back with me. It sounds like the main issue here is with the encoder motor for the transfer case. This is the most common cause of this. I am concerned though that you are getting a check engine light with no code. This tells me that you may have an issue with the power supply to the computer or a communication or voltage issue.

Customer: replied 29 days ago.
Thanks for the reply. I'm going to replace the encoder motor and see where that gets us. Would that explain the "Dremel-like" sound though during deceleration? I'm a little worried something broke off in the transfer case. Regardless, if I need to replace the transfer case I can still use the new encoder motor. I'll update you on Monday after it's installed.
Expert:  FIXITMAN replied 29 days ago.

Yes it would cause this. Please let me know how it goes and we can go from there. Have a great weekend.

Customer: replied 29 days ago.
Terrific news then. Thanks for the fast reply! Have a great weekend yourself.
Expert:  FIXITMAN replied 29 days ago.

Thank you

Customer: replied 26 days ago.
Okay, I installed the new encoder but it still acts as if it's stuck in 4 HI Lock. And when I switch it into 4 HI Lock it has the same behavior. 4 Low works just as expected. Is there anything else less expensive than replacing the transfer case that I can look at?
Expert:  FIXITMAN replied 26 days ago.
Can you tell me if you are getting any noise?
Customer: replied 26 days ago.
No noise now. The only noise through this whole thing was the Dremel sound on deceleration. I confirmed with the tech that changed the fluids that the transfer case was low and smelled burnt (and was smoking). Could something have come apart in there? I don't know a thing about rebuilding these things and the best replacement price I found was $2200 for 3yr/100K (re-manufactured). I'm trying to be positive that's it though before I spend that kind of money.
Customer: replied 20 days ago.
Should I assume this thread is closed? Just checking... Thanks.
Expert:  FIXITMAN replied 19 days ago.

I am still here. I did not see your response. If the fluid smelt burnt and if there was smoke coming from it then that is not a good sign for the transfer case. Burnt fluid is a sure sign that there is an internal failure. That replacement you found is a pretty good deal.