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Random 4x4 engagement

UToffroader

Probationary Member
Messages
3
Location
Utah
I have a 2008 H3 and am having what seems like intermittent 4x4 engagement. I have seen other threads related to the plastic fork breaking but am not sure that's my problem. Its a full time 4x4, and intermittently will grab when turning like the 4x4 is locked. However, during this time I can cycle it from 4x4 to 4x4 low and hear it engage and disengage. As randomly as it engages, it will disengage and operate normally. Occasionally I will hear a pop in the front end when it happens and then it returns to normal. I have replaced both from wheel bearing assemblies as they were bad and I thought they were binding up. Due to the random nature I was kind of heading down the electrical path, transfer case module or switch? But haven't ruled out mechanical issues like a bad axle CV that's binding? Anyone had any issues like this before?
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
Welcome to H4O! I'm moving this to the H3 section unless you say it's actually an H2.

Typically, if the transfer case is engaging it is stuck buttons on the dash. See if there's any play in them and if you can pull one out slightly. Some people have been able to clean these, others have replaced the control panel. You can always disconnect the transfer case encoder motor's electric connection if you think it's electrical (either switches or the encoder failing) though I've not heard of this happening. Usually the worn fork means it won't change from 4HI to other modes, not that it will switch on its own. "As randomly as it engages, it will disengage and operate normally." - are you saying you can hear/ feel the transfer case engaging, or are you just talking about the pop/clunk in the front end?

If the engaging is just the front end engagement, then you likely have a bad front differential with a chunk of metal getting stuck in the gears on occasion.

The CV axles, if they bind, typically only affect motion turns, particularly hard turns.
 

UToffroader

Probationary Member
Messages
3
Location
Utah
Thanks for the reply. A typical scenario is it is most noticeable in a parking lot or during hard turns. When the wheels are turned full either direction you can feel it binding. I always stop at that point and make sure I change the tire angle to make sure I dotn put undo wear on the drive train. At that point I can shift to 4L and hear it cluck when it engages. If I shift from 4H to 4H lock I dont hear anything. I also dont hear any abnormal noise from the front end as you would expect with a CV joint going bad. I will start by disconnecting the motor when I know it is not locked and see if it persists as my start point followed by the replacement of the push button controls.
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
I'd drain the front diff and pull the cover. It's not much work to inspect and if it's all good then you end up with new diff fluid (75W-90 synthetic) anyway. It's a reusable gasket. Many front diff issues are initially attributed to transfer cases, and the diff isn't the strongest.
 

UToffroader

Probationary Member
Messages
3
Location
Utah
I'd drain the front diff and pull the cover. It's not much work to inspect and if it's all good then you end up with new diff fluid (75W-90 synthetic) anyway. It's a reusable gasket. Many front diff issues are initially attributed to transfer cases, and the diff isn't the strongest.

Thanks. Ill start there and maybe the CV axels. Does anyone know what differential is in the front of the H3?
 

Sbc350_h3

Active Member
Messages
27
Location
Hawaii
Not hearing anything going from 4Hi to 4 HI Lock is normal.
The fork is still moving but the plastic is worn and slipping over the coupler. Only takes 3hrs to change to a updated fork. If your mechanically inclined.
 

08H3

Well-Known Member
Messages
1,314
Location
United States
I think I may know what you are talking about. I can't really say I've ever heard a "pop" as you described, but a few times over the life of the Hummer I have experienced what you are describing where it feels like it's in locked 4wd. It's always been a very specific set of circumstances where I am doing a U-turn at full lock (or nearly full) and accelerating quickly. I believe what you are experiencing is tire scrub since you are at a sharp angle. I wouldn't overthink it and worry too much unless there is a more pronounced persistent issue.
 

Sbc350_h3

Active Member
Messages
27
Location
Hawaii
It's for sure your shift fork if it feels like the tires are fighting you in tight turns if you can hear it actuate when you press the lock and unlock button. I've changed my fork after it wore out took about an hour and a half. But I'm also a mechanic. Should be a three hour fix for the novice.
 
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