Autotrack and tire sizes

[jeepstud]

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 tireson 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). While I was doing this I measured circumferences and found them with in 1/4" which is consistent with the radius measurement above.


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. Does the transfer case do some sort of learning and this what it was expecting?

Do I even have an issue here? Hoping done with a lot of experience with these drivetrains will chip in.

[sefiroxx]

Check for worn spots. Happens on my 01 burb when I let the tires get worn down without rotation. Rotating front to back, or turning a single front 180 usually solves the problem.

Worn spot on one will often transfer to the other in the same locale.

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