Max GCWR and SAE J2807

This is a discussion on Max GCWR and SAE J2807 within the RAM 1500 Diesel Towing & Hauling forums, part of the RAM 1500 EcoDiesel Forum category; There is always a lot of discussion on this forum related to how much the EcoD can tow? What is the max trailer weight? Is ...

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Thread: Max GCWR and SAE J2807

  1. #1
    RAM Rookie marahee7's Avatar
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    Post Max GCWR and SAE J2807

    There is always a lot of discussion on this forum related to how much the EcoD can tow? What is the max trailer weight? Is the truck capable? Is the truck "Safe"? etc. I am not a towing professional or an expert so I am always interested in what the guidance charts indicate and what standards were used to create the chart. I have attached the SAE J2807 document with the types of tests that were completed to validate performance at the manufacturer published GCWR.

    I hope this a resource to support many of the experiences given on the forum.

    *****Disclaimer **** I do not advocate towing at or beyond the GAWR, GCWR, or GVWR.

    I do advocate for having technical knowledge to pair with experience (mine and others).

    From my humble point of view.

    The EcoD platform (Engine/Chassis) is capable of meeting all of the SAE J2807 tests for towing up to the manufacturer provided GCWR and therefore the TRUCK is SAFE up to listed GCWR (while keeping GAWR/GVWR within spec). Many of the tests listed are more stringent than the conditions I would normally tow my rig. Although it is nice to see that I should be able tow a GCWR of 13,750 lbs from Bull Head City, AZ to the Union Peak Pass in the summer (ambient air temps >100 F) and not drop below 40 mph. I can even keep my A/C blowing at max cool.

    What is not "SAFE" about towing at or above the GCWR?
    1. Weight/Balance of the tow vehicle/trailer WD system (search the forum for the sage advice on this topic @ VernD and others)
    2. Tire/wheel selection
    3. Driver Experience
    4. Vehicle/Tire maintenance (Truck/Trailer)
    5. Weather conditions like precip and wind
    6. Extreme emergency maneuvers beyond the test conditions set in the SAE standard.
    7. Add your own to the list as you wish.

    From the SAE J2807 tests it is possible (although maybe not strictly advisable) to extrapolate the following argument:

    Example: CREW CAB - 5'7" Box, 4x4 - See Ram towing Chart

    5.7L HEMI with 8HP70 transmission 3.92 gear ratio has a GCWR of 15,950 (assuming you keep GAWR/GVWR in spec).
    3.0L EcoD with 8HP70 transmission 3.92 gear ratio has a GCWR of 13,750 (assuming you keep GAWR/GVWR in spec).

    GCWR Difference is 15,950-13,750 = 2,200 lbs. What accounts for this difference?

    Well, GCWR is provided by the manufacturer not SAE. SAE simply tests the vehicle at the manufacturer provided GCWR and scores the test PASS/FAIL. Hard to tell why RAM gives the different GCWRs, but we can assume a little more.

    What is different between the two example vehicles? We might assume it is just the powerplant (Hemi vs EcoD) and the associated effects of the engine weight. Therefore, the chassis of the 1500 is completely capable up to a GCWR of 15,950 (GAWR/GVWR in spec). What component fails above GCWR 15,950lbs is up to speculation, but none of the trucks will pass all of the SAE tests.

    At this max GCWR (15,950 lbs) the EcoD powerplant will not pass one or more of the SAE tests and we don't know which ones. It seems unlikely that stopping distance, structural stability, understeer, or sway response are a function of the powerplant. Therefore, it would probably fail one of the tests associated with EcoD powerplant performance. Here is where the EcoD's GCWR is reduced to 13,750 so that it passes all of the SAE tests.

    How much can "I" tow with my EcoD? I guess that is still a personal interpretation.

    I guess the new question should be.

    What engine performance, warranty, legal issues will I have with my EcoD powerplant if I decide to tow at the max GCWR for the Ram 1500 chassis (transmission, bed length, 4x4,etc)?

    Enjoy.


    SAE Tests Excerpt:

    Tow Vehicle Propulsion Requirements and Level Road Acceleration
    PERFORMANCE ATTRIBUTE PERFORMANCE METRIC REQUIREMENT
    Level Road Acceleration 0-60 mph 30.0 seconds single-rear-wheel/35.0 seconds dual-rear-wheel
    Level Road Acceleration 0-30 mph 12.0 seconds single rear wheel /14.0 sseconds dual rear wheel
    Level Road Acceleration 40-60 mph 18.0 seconds single-rear-wheel/21.0 seconds dual-rear-wheel
    Launch on Grade 12% grade, forward direction Five launches to 5.0 meters (16 feet) in 5 minutes
    Launch on Grade 12% grade, reverse direction Five launches to 5.0 meters (16 feet) in 5 minutes
    Highway Gradeability Minimum speed on grade (Davis Dam) 40 mph single-rear-wheel/35 mph dual-rear-wheel
    Highway Gradeability Drivetrain system performance No component failures, no diagnostic codes that alert the operator, no customer warnings
    Highway Gradeability Cooling system performance No component failures, no diagnostic codes that alert the operator to take service or driving action, no customer warnings, no fluid loss



    Combination Handling Requirements
    PERFORMANCE ATTRIBUTE PERFORMANCE METRIC REQUIREMENT
    Tow-vehicle understeer Understeer* for0.1 g ≤ Lateral acceleration ≤ 0.3 g <0 degree/g
    Trailer Sway Response Trailer sway damping ratio ≤ 0.10 at 100 km/h (62.1 mph)




    Combination Braking Requirements
    PERFORMANCE ATTRIBUTE PERFORMANCE METRIC REQUIREMENT
    Combination Stability Deviation within lane Remain within a 3.5-meter-wide (11.5 feet) lane throughout stop
    Combination Stopping Distance Stopping distance 20-0 mph for TWR ≤3,000 pounds ≤35 feet, except ≤45 feet at any TWR above the tow vehicle’s unbraked TWR
    Combination Stopping Distance Stopping distance 20-0 mph for TWR >3,000 pounds ≤80 feet
    Park Brake Performance Hold on grade 12% grade at GCWR (upward and downward)


    2017_ram_1500_towing_charts.pdfSAE J2807.pdf

  2. #2
    Super Moderator VernDiesel's Avatar
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    You put some time in that. ED vs Hemi Is mostly about the cooling system. ED will fail acceleration up a grade test due to derate before the Hemi. The fact that the Hemi weighs 80 pounds more than our ED is mostly offset by our 6950 GVWR versus 6900.

    My particular VIN Quad cab Big Horn 3.92 Has a max tow of 8800 GCVWR 14,500.

    What is not safe for ED above it’s cvwr but below max Cvwr for the 4th gen is the acceleration test fail via cooling system/ECM derate. Otherwise with aftermarket turbo brake software it’s actually more capable to control descent speed & keeping brakes cool for stopping. For our purposes cooling can be kept in check by limiting sustained rpm to 3K or less. But you can’t do that for j2807.

    I have towed cvw of 15,800 over 6 percent grades on a 1,000 mile trip. Even with ideal weight distribution etc the 1/2 ton platform is pretty much tapped out at 16k. Axles receiver etc etc and in a real world most people won’t get their without somewhat grossly exceeding something simply for the fact that they don’t know the importance & value in setting WDH & loading to meet specs via adjustments according to CAT scale results.
    Last edited by VernDiesel; 07-10-2019 at 08:22 PM.
    marahee7 and Last Train like this.
    Airstream, TT, Boat, transporter. Factory receiver 1,290/12k (w WDH) factory brake controller tow mirrors & hitch camera. No sway WDH, Andersen Rapid adjust hitch, Turnover ball GN hitch w 5er adapter, Axle to frame air bags, GDE tune w turbo brake, SLT Grill, 275/55/20 XL load tires, Max ED tow rating 9,200, Combined axle rating 7,800, Max RAM 1500 CVWR 15,950, truck with me & 3 hitchs axle weights steer 3,340 drive 2,560

  3. #3
    RAM Rookie Siha's Avatar
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    Quote Originally Posted by VernDiesel View Post
    My particular VIN Quad cab Big Horn 3.92 Has a max tow of 8800 GCVWR 14,500.
    Is there a website to plug in your VIN and get the specs/capabilities?


    Sent from my iPhone using Tapatalk

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    Super Moderator Crash68's Avatar
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    Quote Originally Posted by Siha View Post
    Is there a website to plug in your VIN and get the specs/capabilities?
    I don't trust the FCA website VIN look up for truck towing specs, according to it I have 0 lbs payload and a towing capacity of 7500 lbs even though I have 3.92
    I attached the SAE J2807 ratings for the 2017, the 2018 should be identical. Use those numbers and run your truck/trailer over the scales.2017_ram_1500_towing_charts.pdf

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