Changing from 4:10s to 3:42's... trade me

Hey there, my buddy has a 2006 chevy silverado ss with 4:10's and the lq9 6.0l, he's and older guy and gets 13 mpg on highway since new, i was telling him i think his best investment would be 3:42's most likely i told him i would get on here and see what yalls opinion was... im thinking its a 4+ gain in mileage..
What are you guys thinking? if a good idea im sure someone would love to trade some nice 4:10's for some lously 3:42's helll i would love to give him my 3:73's laying around but he wouldnt like the small notice haha.

I got 2 sets I'll trade ya

set for the front and rear? thats what i need, i forgot to mention this is a 4 wheel drive....

I got two that came out the rear, I don't think it'll work on the front. Maybe someone around here that knows will chime in.

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Originally Posted by jansen

I got two that came out the rear, I don't think it'll work on the front. Maybe someone around here that knows will chime in.

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I believe front is 10bolt rear is 14 bolt.

I'd contact http://www.ronsmachiningservice.net/servlet/StoreFront

He could buy everything he needs cheap!

to tell u the truth i got to do some research on the front axle never split one open nor looks fun to do...

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Originally Posted by BrutalSierra

I believe front is 10bolt rear is 14 bolt.

I'd contact http://www.ronsmachiningservice.net/servlet/StoreFront

He could buy everything he needs cheap!

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i beleaive both are 10 bolts..

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Originally Posted by silverado00

i beleaive both are 10 bolts..

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Your right only the 2wd got the 14bolt rear.

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Originally Posted by BrutalSierra

Your right only the 2wd got the 14bolt rear.

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yep did some searching, both 10 bolt, rear is a 8.6 as we all know and the front is a 8.125

that truck will probably get worse MPG with 342s then 410s. get him a tune and a fresh tune up and his mpg should raise up