AWD and mismatched tires

[Meathead16]

I'm helping out a friend with his yukon denali awd w/ the nr3/4481 transfer case that has been making a scraping noise while driving. Basically the slightest imperfection in the road causes a scrape/sqeak noise. Handling feels unsteady as well, like the truck is driving through sand or something. I noticed his front tires are all terrain tires and the rears are all season. There is a noticeable size difference between the two pairs. Obviously this is a big no-no but I'm wondering how much damage could be done, and if getting 4 identical tires on it asap will at the very least stop any further damage from occuring. He didn't know if the tcase fluid was ever changed so I drained it and it was very dark. It was hard to tell if there were any metal flakes in it or not. It sorta had a sheen but not really at the same time. I'm assuming this is because of the mismatched tires. He said it's been like that since March or April.

Has the snowball grown too big to stop or is there a way to mitigate the damages before this thing blows up and leaves him stranded?

 

[PG01]

You said it yourself, unfortunately even the slightest variation in tread depth can cause damage, 2 completely different sizes and types of tires completely f’d the tc. Once there is metal meshing around with gears its only a matter of time. If he’s keeping it id find a jy tc and put some matching tires on it.

 

[swathdiver]

Yep, not supposed to be more than 1/8 inch difference in height between tires and are supposed to be replaced as a set and not in pairs.

 

[Marky Dissod]

Mathematically, largest difference I've EVER seen is 4.10 on one end and 4.11 on the other end.
Only seen that firsthand once in my whole life, and it was close to two decades ago.

Only time I've ever seen different size tires front vs rear is mud racing, where the slip-difference is forgiven by wet mud.

... getting 4 identical tires on it asap will, at the very least, stop any further damage from occurring.

 

[Jason Sewill]

Just get the same size tires. That is where you start. Probably will be fine. But the noise is probably a front pinion bearing. It’s a known issue with GM.

 

[PG01]

Yeah, probably fine

 

[Fless]

As @Jason Sewill commented, get matching tires on it first. Then see if further diagnosis is needed.

 

[Doubeleive]

errr ummm yaaa, sure lol

 

[Meathead16]

Quick video of the noise and associsted play

 

[SpareParts]

Get a different TC or rebuild the TC.

 

[Meathead16]

4 matching tires were just installed a couple days ago, noise is still present. No surprise there just wondering is a full rebuild or replacement necessarily or could it just be the bearings making the noise? The drive has improved with the new tires