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Dave Nova
Dave Nova, GMC Technician
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Hummer H2 stuck in 4Hi Lock

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hello, I write from Italy, I have in my workshop an Hummer H2 with a trasfer case problem I think. Like the dash light say it seem to be in 4Hi (normal street ride), but really it is in 4Hi Lock, because is hard to turn and you feel the truck locked. how can I solve the problem? thanks Damiano



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Customer: replied 4 years ago.
I can say that the transfer case go from Hi Lock to Hi Low Lock and back with no problem, but when I push the botton on dash to choose to go from Hi Lock to HI, the light on dash go in the right position near Hi button, but the car stay in Hi Lock, than when you drive it and turn, you feel that the car is locked and the tires jump a little and rub.

Hello and thank you for trusting me with your question. My name is XXXXX XXXXX I will do my best to help you with your GMC problem.

Do you have the 4 pushbuttons labeled Auto,XXXXX 4 wheel High, and 4 wheel Low?

Customer: replied 4 years ago.
Hummer H2 hasn'tXXXXXoption, is full 4wd Hi, and you can go in 4wd Hi Lock and 4wd Low Lock...
Customer: replied 4 years ago.

and my transfer case is a Borg Warner

The transfer case is full time all wheel drive, you are correct. The lock is for the rear differential. You can unplug the connector at the rear differential to see if this makes a difference. (wires are Black and Light Green)

There is also a locking mechanism in the transfer case, this is what is likely causing the problem. The front and rear drivelines are staying locked together, causing binding when turning. See #16 in exploded view of the transfer case below. Before tearing into the transfer case, it would be best to scan for trouble codes in the transfer case control module (TCCM), this requires the use of an advanced scan tool that can read Chassis codes.


Customer: replied 4 years ago.

I already tried to unplug the connector of the rear differential lockers, but the problem remain. The problem is around the transfer case.

I haven't a scan for the TCCM. Only a scan for generic OBDII american cars and truck, but it didn't found any trouble code.

The generic scan tool is only going to show powertrain codes, not any of the TCCM codes. The problem can either be in the actuator for the locking clutch at the transfer case, or the problem could be in the TCCM. The most common problem would be in the actuator.
Customer: replied 4 years ago.

Then, do you think that the usual problem is inside of the transfer case, in the actuator, in the scheme around parts n° 15-16-17-18?

Or for actuator do you mean the electrical motor outside the tranfer case that shift from Hi to Hi Lock to Hi Low Lock? Do you have a wiring diagrams of this?

The part I am referring to is the actuator (electric motor) on the transfer case that shifts the different ranges. The wiring diagram for the shift controls is below for you.


Customer: replied 4 years ago.

ok, but the actuator shift from Hi Lock to Hi Low Lock and reverse. Than it should work, don't you think so?

Could you give me bigger scheme of the trasfer case and of the wiring diagrams because are difficult to read in this small size.


If you can look at the actuator while shifting into all of the different gear ranges and the actuator moves to all of the positions then the problem is not electrical, it will be a mechanical failure within the transfer case. That is the only size of the diagram that I have. You should be able to enlarge it with photo editing software.
Dave Nova, GMC Technician
Category: GM
Satisfied Customers: 19450
Experience: ASE Master Certification. GM World Class Certification
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