So the other day I parked in some unlevel ice/snow driving in 4wd HI and a chunk of ice popped my back right tire. So I jack it up, put the spare on, and when I leave, all of a sudden I am getting a vibration in the front right and it sounds almost like offroad tires do on the road, that low roaring sound. If I switch it back to 2wd, it sometimes takes little longer to shift back to 2wd, but the vibration and sound go away. If I switch to Auto 4wd or 4wd HI the vibration problem comes back. What could be causing this, why, and how do I fix it?

 

Is the spare the same tire size as the rest of your tires. I know that if you have different size tires on your truck and are in 4x4 it wont like it.

 

x2.

alot of blazers have factory 235/70/15s, but when people replace tires, they put on 235/75/15s. I know my blazer still had a 235/70 spare when I replaced my tires from 75s to 30x10.50s.

thennnnn complicate that with usual under-inflated spares which further throw off the drive line...

 

Yeah the spare is 235/70R15 and the other 3 tires are 235/75R15. So are you guys saying that is the only thing that would cause the 4wd system to act like that?

 

Not the only...but...lemme reference scrubs:

'if you hear the sound of hooves running towards you, go ahead and think horse, not zebra'

 

You cannot mismatch tires like that and expect everything to work properly. There is 1" difference in overall diameter between a 235/70R15 and a 235/75R15 tire. That is a LOT, especially on a vehicle with no center differential.