Where are you getting this "1% is OK" bullshit from? 1% tire mismatch will burn up the t-case almost as fast at 5%. The allowable mismatch is one that will not exceed 5 revolutions per MINUTE, at the transfer case. (NOT the f ucking tires).
I came up with 813 revs per mile for a 275/45-17 tire.
1% of 813 is 8.1, so add to 813 = 821.1.
Multiply 813 X 3.42 axle ratio = 2780 revs per mile
Multiply 821.1 X 3.42 axle ratio = 2808.2 revs per mile.
Find the difference: 2808.2 - 2780 = 28.2 revs per mile difference at the T-case.
Now, how fast can you go before you exceed the 5 rev per MINUTE limitation?
28.2 / 5 = 5.64 X 60 (to convert revs in a minute to speed in miles per hour) = you can only go 33.84 Miles Per Hour before the 5 rev per minute limit is exceeded with your "1% mismatch".
Again, I don't know where you got this 1% from, but it isn't close enough. You MUST multiply any mismatch by the axle ratio, because that's what the T-case 'sees'. If you want minimum t-case, axle shaft and u-joint stress. Long v-clutch life, minimum tire wear, and the minimum effect on fuel economy, front/rear tire match needs to be just about perfect.
There are perhaps 3 guys on here that understand how this t-case functions, have run it long enough (I've owned them for 19 years) and have had enough of them apart (at least 15 of them) that know what they're talking about, and what tears these up or allows them to live. I'm one of these 3 dudes.
I've had these run 150K miles with no wear on the thrust washers, no overheating of the fluid, and no locked-up v-clutches, busted prop shafts, or other broken parts. The tire match was PERFECT. I measured tread depth regularly, and rotated front/rear every 15Kmiles. I also got over 175K miles from those tires.
I've been on here a long time. This "How much mis-match is too much?" debate never ends. The guesses and peeps not knowing WTF they're talking about never ends. My observation is that the t-cases that burn up are in trucks with mismatched tire sizes. Maybe not immediately, but eventually the v-clutch is damaged. The t-cases that don't ever burn up (or break other parts) have matched tire sizes. End of discussion.
The guys that don't have trouble at all run 4 matched tires. I'm one of these guys. And I DO know WTF I'm talking about on these T-cases. I don't care if you listen or not. Go ahead and run your "1%". Take a 1,000 mile trip at Interstate speeds, and I can just about guarantee your NEXT T-case will be junk just like your last one was in 100 miles.
It's the mismatch at the T-case that matters. It can't be over 5 per MINUTE at sustained highway speeds. Do the math, and decide for yourself.
