Auto 4wd Vibration and Tires

[Krummelt1]

I am posting today to reach out and see if anyone else has experienced a similar issue. First some background: I recently purchased a 2009 Tahoe, 128K miles. By all accords in excellent condition.Except it needed 2 rear tires. How it got to just two I do not know. The front tires had ~20K miles on them and were worn to ~ 8/32. Tires are Michelin LTX MS2 . New depth is 12/32" . I decided to put just 2 tires on it. The new tires went on the back.

On my trip home I put the vehicle in "Auto" 4wd (it has 2wd, Auto, 4WD and 4LO) and noticed a vibration I had not noticed before. It wasn't awful or grinding but noticeable nonetheless. A very slight vibration and slight noise. I could not be certain though since the vehicle was new to me. I thought maybe I was just over analyzing and paying "extra" attention.


Today I put the new tires on the front and the older tires on the rear. This then matched the condition prior to the new tires. The "larger" pair of tires on the front. The vibration went away. Aside from a very low noise I cannot tell whether I am in Auto or 2WD just as it had been before I got the new tires (with them in the front).


Does anyone have any experience why I would get vibration with the slightly smaller tire on the front but not the back? I don't think it is balance as it goes away when I am in 2WD.

Do I even have an issue here?

 

[Krummelt1]

Oh yea I forgot to mention I measured the circumference and found the old and new tires to be 1/4" difference in circumference. This is consistent with the radius difference in tread depth.

 

[Mkr88x]

I just bought a 08 and having the same problem. No noise until i put it in auto or 4hi, its really quiet but its there. I read somewhere it could be a tire issue, and my fronts are just about gone, and my rears still have like 70% tread left

This is also what someone said on this forum " if you are only getting the noise in auto or 4wd, the problem is inside the front differential or the driveshaft. 90% of the time its the carrier bearings"

 

[swathdiver]

You might check with your local dealership to see if your truck had the Transfer Case Module (TCCM) updated (computer program) as there was a notice about a slight chain moan in Auto/4HI. Other than that I do not see how they're related. The part number for the program is 24246032.

The front hubs generally need replacing around this time mileage wise. Was the differential fluid in the front and rear and transmission and transfer case changed? They all should have been done at at least the 100k mile mark. Dirty old fluids can make the truck feel like its wanting to go in different directions. Start with the simple stuff.