Outer Limits 4x4 Board

hi all

i have 31" on my '90 sierra w/t, 1.3 diff's and 1.3 tranny,

what percentage of reduction in high range do i need to fix my speedo and get my gearing back to stock'ish region???

i can find info on what % difference (eg. 4.9:1 = 115% in low and 16% in high and/or 8:1 = 250% low and 24% high) but nothing to say "running 31" with stock 1.3ltr w/t running gear (eg. diff & tran) you need ???% reduction"

any idea???

the reason why is when i had 29" wheels i kinda (needed a tad lower) liked the gearing level and want to know what % i need to achieve this

thanx guys n gals

You need 5.14:1's or 6.5:1's for 31's, but if you plan on going bigger I would go the 6.5's, because now that I have gone up to 32's my 5.14's are a tad too high.

31's are basically 19% taller than 26" stock tyres.

Bear in mind that 31's present more rolling resistance and aerodynamic drag, and are heavier, and you need more than 19% more reduction to get the same actual performance.

That's on paper. Real world- pretty much any transfer gear set will feel OK with 31's on it from a gearing standpoint on road. How much low range you need will depend on the type of terrain you are driving and your driving style.