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Thread: Rear end gears

  1. #1
    Sr. Apprentice Bigmacnchez's Avatar
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    Exclamation Rear end gears

    I'm running 24" wheels and 32.75" tall tires with my stock 3.73 gears and open diff. I'm wanting to re-gear it. I want either 3.73 to 4.10 with either a 33 or 35 inch tall tire at the end closer to 3.73. I know someone is going to tell me to grab a calculator. Already got one. I guess in my older years I can't remember the formula. Please help lost lots of power from bigger wheels 7" taller.
    2005 Chevy Silverado 1500HD 6.0 BBK headers,Cold air intake, Flowmaster cat-back, Diablo Trinity tuner, 22" KMC Rockstar Cooper ATZ, Kenwood DNX-9980HD indash, 2 Kenwood XR-W10F under back seat, Kicker 11DX10001, Kenwood KAC-7205, Polk Audio DXi6500 6.5"Component Speaker System front and back, Smoked out lights, 12K Hid's HI/Lo. Code Alarm W/remote start.

  2. #2

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    Quote Originally Posted by Bigmacnchez View Post
    I'm running 24" wheels and 32.75" tall tires with my stock 3.73 gears and open diff. I'm wanting to re-gear it. I want either 3.73 to 4.10 with either a 33 or 35 inch tall tire at the end closer to 3.73. I know someone is going to tell me to grab a calculator. Already got one. I guess in my older years I can't remember the formula. Please help lost lots of power from bigger wheels 7" taller.
    This Gear Ratio and Tire Size Chart, should be able to help, with which setup "Gears/Tire Size" will give you the Best in Fuel Mileage and/or Performance.


    MIKE


    99"SILVERADO
    5.3 l 3.73 l G80
    BLACK BEAR CUSTOM TUNE
    SNUGTOP l COLORMATCH l KATZKIN










  3. #3

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    so here is one formula for gear ratio which can be used to find what you want. There was a thread on it a while back if I can find it.

    (New tire diameter/old (stock)tire diameter) x original gear ratio = New gear ratio

    ie. (35/31) x 3.73 = 4.21
    so if new tire size is 35 and the stock tire was 31 you get 1.129. multiply by gear ratio 3.73. this gives you 4.21 which isnt made. you then need to choose a 4.10 or 4.56. The 4.10 will give you lower highway rpm but you will lose low end grunt. To find your effective gear ratio (so just tire change) just flip the old and new tire sizes.

    Here is a decent online source to just plug it in http://www.4lo.com/calc/geartire.php

    My personal opinion is 4.10 with 33's and go to 4.56 with 35. I basically have your truck in a 4x4 and currently run 4.10 with 35's. Did that mainly as I drove it daily with a large portion of highway, and I can definately tell the difference when I tow. If I start towing more, and its no longer a daily driver, I am considering regearing to get it back closer to the performance of the stock ratio.
    David
    2004 Silverado 2500 Crew Cab 4x4, AMSOIL EA air filter, Granatelli MAF sensor, Throttle body spacer, Magnaflow exhaust (true dual to 2 in 1 out muffler), 6" ProComp lift (add a leaf and 5" superlift rear block), Bilstein shocks, 35's (Cooper Disoverer ST) and 4.10 gears, Rhino Liner, EGRUSA fender Flares and widow visors, extended stainless steel brake lines, firestone airbags w/onboard air compressor, Pioneer Avic X940BT navigation, Accel backup camera.
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  4. #4

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    I assume you used that tuner to re-program the ECU for the larger diameter tires?

    My 2008 Silverado I used to own had 20" wheels with 275/55 R20 tires. Those tires were 31.91" tall, I also had 3.73 gears with a 4 speed auto. I noticed no loss in power at all. Granted your current tires are 0.85" taller.

    If you do decide to go with 35" tires, 4.10 gears would be in order.

    2013 Silverado LTZ White Diamond Crew Cab


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  5. #5

  6. #6

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    Silly question but I simply don't know: when you regear the rear end, do you replace just the internal gears or the whole axle?
    Clint (TX) 2001 Silverado LS 4.8L auto 2wd ECSB [GARAGE]
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  7. #7

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    internal gears. Just the ring and pinion. Master install kits will have shims and all that, but its basically just the stuff in the middle of the differential.

    So for example my truck
    Ring and pinion
    http://www.ringpinion.com/b2c/Produc...rce=DiffWizard

    and master install kit (bearing etc)
    http://www.ringpinion.com/b2c/Produc...rce=DiffWizard

  8. #8

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    Quote Originally Posted by dsfloyd View Post
    internal gears. Just the ring and pinion. Master install kits will have shims and all that, but its basically just the stuff in the middle of the differential.

    So for example my truck
    Ring and pinion
    http://www.ringpinion.com/b2c/Produc...rce=DiffWizard

    and master install kit (bearing etc)
    http://www.ringpinion.com/b2c/Produc...rce=DiffWizard
    Good info! I am wanting to get my truck re-geared. Thanks
    2010 GMC SIERRA CREW CAB (Silver) 4x4, ReadyLift 2.5" Level Kit, 305/60/18 Dick Cepek Mud Country, Go Rhino Nerf Bars, Husky Liners front and rear, Bushwacker Bed Rail Caps, Custom tuned. 4:11's

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