Suburban rear axle into C1500?

Discussion in 'Axles + Brakes' started by Jerryred94silvy, Mar 16, 2021.

  1. someotherguy

    someotherguy I'm Awesome

    Likes Received:
    Sep 28, 2013
    Houston TX
    "most 400's I find in the junkyard are beat to hell"
    "10 bolt axles get a bad rap"

    Which one is it?

    The 9.5 is tough enough that often you can just find one and install it. Sure, check the brakes.

    Nobody is suggesting that every hobbyist knows how to build a rear end. Many can install a locker, though. If most of the enthusiasts you know don't know how to work on their own vehicles, you don't know enthusiasts, you just know people with vehicles. :D

    You can quit defending the weak-ass 10 bolt. It's a differential, not your mother.

    stutaeng, Schurkey, Jglew82 and 2 others like this.
  2. stutaeng

    stutaeng I'm Awesome

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    Aug 7, 2019
    Dallas, TX
    I've looking at doing a 14b swap on my 1500. I saw on one thread at the website a guy quoted these numbers on the GM axle torque ratings:

    10 bolt
    8.5" = 3,800 ft lb

    14 bolt
    9.5" = 5,000 ft lb
    10.5" = 6,242 ft lb
    11.5" = 8,321 ft lb

    I'm not sure if they are official or not, but a 9.5" gets you 1,200 ft lb of extra "beef" capacity over a 8.5". Note that the diameter and strength relationship is not linear. i.e.: a 17" (twice the diameter of the 8.5") ring gear will not be twice the torque rating of the 8.5", but much, much higher. I'm positive the 10.5" has a higher torque rating than the Dana 60!

    The engine torque is multiplied by the gearing of the transmission and axle. That's the torque that axles shafts see under pure engine torque, without drivetrain friction losses.

    For example, take a 5.7 L31 with TQ of 330 ft lb using the first gear of a 4L60 of 3.06 and 3.73s they usually came with: 330 ft lb x 3.06 x 3.73 = 3,800 ft lb. Marginal.

    Take a 6.0 LS with TQ of 360 ft lb using the first gear of a 4L60/65e of 3.06 using 4.10s: 360 ft lb x 3.06 x 4.10 = 4,520 lb ft! I believe that's the setup of the GMT800 Silverado SS and those had the 9.5" 6 lug axle (TBSS also I'm sure) following me?

    Clearly the torque of a diesel/BBC required a variation of the 14b, which is no surprise. Or any souped up engine pumping out big numbers, extreme ratios, etc. for that matter. I mean, those are peak torque numbers and that's assuming your wheels are somehow locked, which is obviously not going to happen under daily driving conditions, unless you are doing something stupid, LOL. More like using slicks on the strip or rock crawling or bogging.
    Last edited: Apr 8, 2021
  3. Fast_Z71

    Fast_Z71 Newbie

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    Nov 23, 2020
    United States
    The same people that say the 8.5 in is a week axle are going around and shaving 11.5 and 10.5 in axle to gain “ground clearance”. If you look there’s only 3/4 of an inch difference on from the D60 and the 11.5 in but that’s for another day. I’ve your just DD or you do light off-roading your truck whether it’s stock or running 33-35s the 8.5 should hold up to the task. Now I will say if you’re running more than a 35 I’d definitely look in to getting a different rear end or if you’re running any kind of real power. If you can find them a 9.5 in 6 lug with upgraded 33 spline axles and a TT is a great upgrade for a 1500.
    Last edited: Apr 13, 2021
    Jerryred94silvy likes this.

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