2011 Avalanche Axle Swap

Discussion in 'Chevy Avalanche / Cadillac EXT' started by David Smith, Oct 6, 2019.

  1. David Smith

    David Smith Full Access Member

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    Hey guys,

    I have done a few searches, but have not found what I am looking for yet. I have a 2011 Avalanche with 3.08 gears. I have a boat that weighs roughly 4-4500lbs. Towards the top of this trucks capacity. I was curious how much of a difference I would actually be able to expect if I swapped to the 3.42 axle. On flat ground it does alright at 60 or below. If I try and go 65-70 while towing, it will run at a pretty high rpm. In the slight hills of northern GA, this truck is an absolute pig. At times, I felt like I might not make it to the top of some of them.

    I was also curious if the 3.73 gears from a tahoe or 1500 would be better, or too much. This is a factory truck.

    Thanks for y'alls help!
     
  2. iamdub

    iamdub Hold on... Lemme overthink this for a bit...

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    I don't know about the '09+ with the 6-speed transmissions, but on my '08 with the 4-speed, the factory trailering package included 3.73 gears. I'd imagine the newer ones such as yours would be the same. If you don't tow enough in relevance to your normal driving to go "full-tilt" with the 3.73, then the 3.42 would be an 'okay' compromise. Cruising on flat land at 70MPH, I'm turning 2,000 RPM and averaging around 19MPG with no AFM. I got almost 21MPG with AFM. Keep in mind mines a Tahoe, so it's shorter and possibly lighter than your Avalanche.
     
  3. avalonandl

    avalonandl Full Access Member

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    3.73 the best

    Can't do that if its 4wd
     
  4. swathdiver

    swathdiver Full Access Member

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    David, aren't you the guy that picked this one up at work and rebuilt it? A Z71 right?

    If 4x4, with 3.08s the towing capacity is 4,900 pounds. The 3.42 gear brings it up to 5,400 pounds. What brings it to the max pulling power is increasing its ability to shed heat from the powertrain, the engine oil cooler, external trans cooler, bigger radiator, 700 watt fan motors, etc. 7,900 pounds this way. Add 200 pound to each if it is a RWD truck.

    Yes, the gears make a big difference and you could also run 3.73s easily.

    3.08s at 70 MPH in 4th is 2677, 5th is 1980 and 6th is 1550. Stock tire height for all, but at 8/32 tread depth.

    3.42s @ 70 MPH in 4th is 2973, 5th is 2199 and 6th is 1721. These are mathematic calculations, not taking converter slippage into account or worn tires.

    3.73s @ 70 MPH in 4th is 3242, 5th is 2398 and 6th is 1877.
     
    Last edited: Dec 8, 2019
  5. BG1988

    BG1988 Full Access Member

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    is this a 5.3?

    even the hyhoe can do 6200(2WD) with the 3.08 (must be in M gear)


    should have gotten a hoe or sub they have higher tow capacity
     
    Last edited: Dec 12, 2019

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