Pardon the noobie question, but how can I determine (other than the lights on the control panel,) if my 2006 H3 is in 4 high or 4 high lock? Here is why, after using 4 High lock during a two day snow storm I switched back to 4 High and have now note a humming coming from the front end. This humming sounds very much tire wear starting (I have 35 inch Cooper Discoverer AT3 with 9k on them). I can feel it in the steering wheel and the sound increases as speed increases. I did follow the owners manual instructions regarding backing up for 25 feet while turning after pressing the 4 High button. If I turn full lock on drive pavement in either direction there is no significant tire scrubbing feel or noise. I did rotate the tires and there is no change in the humming sound. I have previously changed the fluid in the TC about 15k miles ago. New hubs 20k miles ago. I have looked through the forum and seen several methods of repair, but cannot find a way to confirm the issue. I'm torn between tire wear and a 4 high lock issue. It could just be a big coincidence, but I'd like to be sure.
So is there a test to determine 4 high vs 4 high lock short of tearing down the TC?

 

There is a differential in the transfer case, works the same as the ones on the axle. Select the four high not locked and drive the Hummer about 10' to ensure the encoder motor has selected it. Chock one axle, front, and jack up the another, rear. Put the transmission in neutral. Spin the driveshaft of he jacked up axle, rear, by hand. The same can be accomplished by jacking up one wheel and spinning it. If it spins the transfer case is not locked.

 

If you don't feel any tire scrubbing or stiffness in tight low speed turns (3 mph in a parking lot) I'm going to say you are NOT in 4HI LOCK.
Noise can be coming from hub bearings, half shafts (CV shafts), front differential, front prop shaft (drive shaft) CV or u-joint.

 

Thank you for the fast response!
Following the instructions from WR3NCHE4D I have ruled out the vehicle being in 4 High Lock. It passed both tests. I have to admit I don't fully understand exactly how that all works that's why I am so grateful for the advice.
I'll now move on to an inspection of the areas that TAINTER pointed out.
Anything special I need to know about this?
I believe that the front bearings will click or grind when you are in reverse. There would also be up and down play in the effected wheel when it is jacked up.
Half shafts , prop shafts and u joints will be loose , show visual signs of damage (leaking) and can click when in reverse.
I'm not really sure about the front diff. Is there a test for front diff issues?

Thanks again for the help!

 

You never mentioned changing the front U Joint. How many miles on it since the last fresh front u joint? They make funny noises too.

Just because you changed front hubs 20K miles ago does not rule those out. What brand did you use? Some are for krap and die quick with off road tires. Any bearing play in the fronts?

 

Honestly Doc Olds I have never changed my front u joints at 117K miles. Not sure if it matter but my H3 has seen very little off road use.
As for the hubs I do not recall the brand but I can tell you I got them at Rock Auto and they were not AC Delco.
I can feel the vibration in the steering wheel, I note no difference when cornering left or right at any speed. I can also feel some vibration in the floor pan.
Again, might just be tires humming but the abrupt start of the noise has me concerned. Also only 9 k on the tires and they have been rotated every 3k miles.
I'm going to try to getting the front end up off the ground and do a visual inspection this weekend. Kinda cold out there in NH this time of year!
Thanks for the the time and advise so far.

 

Depends on where in NH. I have family in Newmarket and it has been mild there after early snow this year.

 

You mean it depends on the DAY Doc Olds!
64 high temps last weekend, negative 6 overnight low expected tonight!

 

So I got the front end jacked up. No looseness detected in the hub ( no slop up and down or left to right) same with all the u joints. I did note a drip of front diff fluid on the drivers side of the diff.
I'll be draining and refilling that just to be sure there is the correct amount of fluid.
I can find the spec for 75w 90 fully synthetic however I cannot find the capacity in the owners manual.
Anyone know the capacity of the front diff of the top of their head?

 

If you are changing diff fluid, buy 4 quarts & do both diffs.