2015 Silverado-3.08 gears with 285/70/17

jzaldivar · June 1, 2015

Hello ALL,

I just bought a 2015 Silverado 4x4 Crew Cab and too my HUGE disappointment it has 3.08 gear ratio! I guess its my fault but I saw 3.42 under standard equipment and failed to view any other info on the sticker. Called customer support in hopes I can get an upgrade since the sticker was misleading....

Anyway, I hate the look with the stock 255/70/17 so Im planning to bump up the size to 265/70/17 or 285/70/17 but I'd hate to ruin the already compromised performance. Any input is appreciated.

Also is upgrading gears possible and what would it cost?

Would upgrading the tires affect too much?

NoProblem · June 1, 2015

I test drove a 3:42, ran it like I stole it, I got out of that truck and right into a 3:08 specifically to see what the difference was - I could not tell any difference at all. Remember that these are supposed to be trucks, not performance street rods.

I still have the stock 18"s on mine but doubt you have to worry about losing any performance by switching tires.

GRN69CHV · June 1, 2015

Swapping gears can be done, it's expensive. Guys are being quoted approx. $2,000 (or more, depending on if you need to replace the stock carrier). Stock GM gears use a different carrier for 3.42 rear axle gear set. Going from a 255/70-17 to a 285/70-17, doubt you'll really notice it at lower speeds, the trans has some deep gearing in gears 1-4, you'll notice a loss in power in the higher gears from both tire diameter and added tire weight (fairly sure most 285/70-17 tires are load range E, tire weight jumps from 38-40#/tire to about 50#/tire. My '15 has the 3.08 gears, probably 90% of the time I drive it in M5 which both keeps it out of that deep 6th gear overdrive, and, keeps it out of V4 mode. Maybe, 1/2 mpg difference in rural driving. I drop it into 6th when on the highway.