Let me ask anyone notice any big power loss or hard time moving 31's because of the drop in gearing? I did the calculator and it said from a stock tire and 3.42's you would have to upgrade to around 3.63's or something to keep the gearing around stock etc but without re gearing it would drop the ratio down to 3.23. Did anyone notice a power loss or a struggle moving the tires?

 

Sure you're going to have a "power loss" of sorts. The drivetrain is turning taller tires. I believe it's from 3:42 - 3:73 - 4:11 - 4:56 are the available gears for us. But you'll get more grip/less spin because of the taller tires but 31's aren't that much taller than the stock 235 75 R15's...
from the online tire size calculator

 

Not really sure if this applies to your rig but when we change tire size, gearing etc. the ECM needs to be re-calibrated to change shift points, speedo and so on. You could buy one of the available units or see if a dealership would do it. Good Luck, Hope this helps.

 

X2 on what the mutt said
I had to do that on my blazer with the 32's

 

actually blazers are more fuel efficient with 31's on 3.42's but yea you will lose some power

 

Lower RPM's at highway speed FTW... if you want to pick some gearing up again just bump to 3.73's, you'll have to do it in the front too though...

 

go for some 4.10's to get some more "horse power". really doesn't increase your hp but you'll truck will move a little better

 

Yeah i was going to re mail back my tune and have it calibrated. Where was the power exactly lost in rpm range? And was it badly noticeable?

 

no not really. blazers are slow to begin with..

 

My fiancee never fails to inform me of this haha.

Can't wait to be able to put 31s on here. It will be a while though