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  1. #1
    Seasoned Camper
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    M399TH 8k Axle Upgrade

    We're looking hard at a new M399th, and I'm concerned about GVWR. It won't take much (about 800#) to hit the 20k max loaded "wet" with our toy in the garage. This begs the question:

    Does the 8k axle option increase the maximum GVWR for the coach?

    TIA

  2. #2
    Site Team WhittleBurner's Avatar
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    Yes it does increase , by exactly how much I don't know but would guess at the min 1000 pounds. Call GD and ask for the Momentum sales Rep, he should be able to give you the best answer.

    If I were buying a new Momentum or Full Solitude (not the S class) that axle would be the first upgrade I would want. We have always felt that CC is one of GDs biggest weaknesses.
    Marcy & Gary
    2014 Grand Design - Reflection 303RLS
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    2015 GMC Denali 3500 - Retired
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  3. #3
    Seasoned Camper
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    Thanks for the reply. I sent GD an email, but no response yet. My dealer says he spoke to the Rep, and he said you gain about 700#. If true, I can live with it.

    I'm still trying to find out what the stock pin box specs are.

  4. #4
    Seasoned Camper
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    Chuck are you talking about the standard 8k or the MorRyde (IS) 8k upgrade
    2018 Ram CC,LB DRW Longhorn 6.7, AISIN, 4.10s

    2021 Momentum 397TH-R

  5. #5
    Fireside Member Rockdaddy's Avatar
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    My 395m was just built with the 8k axles and they come with a tire upgrade to cooper load range H, I asked GD if that would increase my CCC on the sticker and he shot me a quick sure would, but quickly corrected himself saying it would still have the same pin box so the sticker would still say 20K. That being said you know the 8K axles and load range H tires will have an impact on those numbers but most likely will remain unofficial for the time being.
    Mike and Renee with Gracie our Golden Retriever on a full time journey exploring our great Country
    2021 Momentum 395m with Factory installed 8k axles with disc brakes and solar package, 4976# CCC
    2015 F350 CC LB DRW. Firestone #5000 air bags with Air One remote control and Bilstein shocks
    25k B&W Companion on factory 5th wheel mounts

  6. #6
    Site Sponsor Crazybanshee's Avatar
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    Our 397th weighs 22,000 lbs. 6000 lbs on the hitch and 16,000 lbs on three 7,000 lb axles. So I am nowhere near the capacity of the axles. Spending the money to upgrade the axles doesn't seam it will make any difference.
    2007 Volvo 780 VNL Trailersaver Hitch
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  7. #7
    Site Team Second Chance's Avatar
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    In a recent thread in the other sandbox, GD's official response on GVWR and the 8K axles/tires/wheels/disc brakes upgrade was that it would increase the GVWR - by 1,000 lbs. if I recall.

    Rob
    U.S. Army Retired
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  8. #8
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    Quote Originally Posted by Rockdaddy View Post
    My 395m was just built with the 8k axles and they come with a tire upgrade to cooper load range H, I asked GD if that would increase my CCC on the sticker and he shot me a quick sure would, but quickly corrected himself saying it would still have the same pin box so the sticker would still say 20K. That being said you know the 8K axles and load range H tires will have an impact on those numbers but most likely will remain unofficial for the time being.
    That's interesting. I'm being asked to select the axle option as a separate item from the H tire option. Each has it's own price.

  9. #9
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    Quote Originally Posted by Akfiredog377 View Post
    Chuck are you talking about the standard 8k or the MorRyde (IS) 8k upgrade
    I believe it's the "standard". I've not even been shown the MoRyde.

  10. #10
    Fireside Member Rockdaddy's Avatar
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    Quote Originally Posted by Chuck.N View Post
    That's interesting. I'm being asked to select the axle option as a separate item from the H tire option. Each has it's own price.
    I ordered the 7k axles with disc brakes from the factory but that somehow got changed to the 8k, the tire option didnt show up till a few weeks later I called my salesman about it and my order was changed at GD factory, and right before they built it I called GD to verify the rv order along with the called in upgrades. This is when i found out i was getting 8k axles and disc brakes and that the tire upgrade was part of this package I believe I paid $3500 for all that, so i called my salesman again and asked if they were going to double charge me for the tires and they took off the charge from their end, and since my 395m is in transit and i wont take possession for the next couple of days I really wont know what I got till i look at it, but on paper I should have 8k w/disc brake and tire upgrade.
    Mike and Renee with Gracie our Golden Retriever on a full time journey exploring our great Country
    2021 Momentum 395m with Factory installed 8k axles with disc brakes and solar package, 4976# CCC
    2015 F350 CC LB DRW. Firestone #5000 air bags with Air One remote control and Bilstein shocks
    25k B&W Companion on factory 5th wheel mounts

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