2005 Yukon xl 4x4 qudrasteer 57000

I was wondering if anyone has insight into the noise I get when I engage the 4x4HI. It sounds like a rearend whining noise. When I start to slow down, the noise gets louder. Any thoughts? I also get a crunking noise every once in a while when I am braking. I can't find anywhere were something might causing the noise

Since you bought it used, hard to say what the previous owner did or did not do to the truck.

First thing I would do is drain the transfer case fluid, and draw a sample to send to an oil lab for testing of metal and debris content.

Secondly, I'd inspect the transfer case for a weep hole on the side, in the output housing. There is a condition known as pump rub, where a retaining clip that holds the pump can unseat, and subsequently create an interference point that rubs a pinhole through the transfer case.

This hole, at it's worst, can look like an 1/8" to 1/4" square window, through which most of your transfer case fluid can leak.

This condition is more often reported with the diesel trucks having the NV261 and 263 transfer cases. The YukonXL has the NV246 transfer case, where the "pump rub" issue has not been reported as often.

One clue as to whether this problem afflicts you can be had when you drain the transfer case fuid. Drain it into a clean container and MEASURE the old fluid that you drained. Did you get 2 quarts out? If not, then your transfer case was desperately low on fluid. Clue 1.

Next would be to look on the side of the transfer case for oily dirty residue on the right hand side (muffler side) near the forward, thicker end of the tail housing. Lots of black oily residue, with a concentrated point? Clue 2.

Then go to www.thedieselplace.com and search "pump rub". After spending several days reading about the issue, and looking at the pictures, you will have Clue 3, which will determine whether or not you have this issue.

Regardless, know that the main transfer case internals are spinning AT ALL TIMES, even in 2WD, so the fluid should be replaced every so often... like every 30,000 miles.

Lastly, I'd have your rig scanned for any latent codes, just to see if any are there.

thank you for your comprehensive answer, I will look for the problem pump rub, again thank you

Quadrafacts would be considered the QS knowledge guru. Your always there and always knowledgable. Much appreciated.