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  1. #1
    Setting Up Camp
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    Ford 7.3L Godzilla 3.55 vs 4.30

    Anyone have experience with the new 7.3L gasser from Ford and the different axle ratios? I am purchasing a new 37’ TT with 11,000 lbs GVWR. Looking at a F-250 7.3L but it seems like the 4.30 axle ratio is hard to find. How much of a difference does it really make and is it worth it to do a special order if I need to?

  2. #2
    Long Hauler Canyonlight's Avatar
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    Quote Originally Posted by cbarkson View Post
    Anyone have experience with the new 7.3L gasser from Ford and the different axle ratios? I am purchasing a new 37’ TT with 11,000 lbs GVWR. Looking at a F-250 7.3L but it seems like the 4.30 axle ratio is hard to find. How much of a difference does it really make and is it worth it to do a special order if I need to?
    There have been several threads on the new 7.3. If you wish, do a search using Godzilla and you will find about 20 threads. You may not find exactly what you are asking but you can PM folks in those threads and I am sure they can help.

    Here's what I found using godzilla in this link:
    https://www.mygrandrv.com/forum/thre...php?do=process

    Dan
    Dan & Carol
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  3. #3
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    One difference is @65 mph using 3.55 gears you'll turn 1471 rpms in 10th gear. 4.30 gears you'll turn 1782 rpms. Thats with 275/70/18 tires.
    At 60 mph in 6th gear you'll turn 2738 with 3.55. 4.30's will net 3316. 7th with 4.30's will net 2611.
    Looks like basically with 4.30's you're dropping one gear+. Biggest advantage will be from a standstill. The 4.30 will allow better acceleration. With the 10 sp you can find a similar rpms when towing as 4.30's with the 3.55's by down shifting so it's really a wash out on the hwy. IMO. Empty mpgs may take a hit.

    https://www.crawlpedia.com/rpm_gear_calculator.htm
    Last edited by goducks14; 10-22-2020 at 09:27 AM.

  4. #4
    Big Traveler Grandesigner's Avatar
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    That is a decent jump between ratios. I would guess if you will tow more than not, 4.30 might be worth it, especially on challenging terrain.
    Dan and Rita
    2021 Reflection150 260RD, built June 2020, w/400W solar + 2 size 31 AGMs, added 2" lift blocks to match the
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  5. #5
    Big Traveler Txfivver's Avatar
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    I know it's apples to oranges comparison but on my 6.7 the 4:30 gears makes a big difference getting up to speed on a short on ramp for example. My last 6.7 had 3:55 gears and pulled fine but definitely wasn't as easy to quickly get up to highway speed if needed.
    The 4:30's give any engine so much more "leverage" to get a load moving. Good example was the 10 speed bikes we all had as kids, starting out in 8th or 10th gear (3:55's) was hard on the legs!
    2019 Solitude 375RES Onan 5500 Splendide W/D Samsung res. fridge
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    Jeff

  6. #6
    Setting Up Camp
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    Quote Originally Posted by Grandesigner View Post
    That is a decent jump between ratios. I would guess if you will tow more than not, 4.30 might be worth it, especially on challenging terrain.
    This will be my daily driver so I will be not towing much more than I will be towing. Most of our camping trips are long weekends within three hours.

  7. #7
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    I had 4.10's on my Ram 6.4 Hemi. I specifically looked for 4.10 and 4.30 in Fords. I can't compare to the 6.2 or 7.3 but I wanted to have the biggest advantage from a power perspective when towing. I'm retired and my DD consists of short hops around town. DD mpg's don't matter much to me. I'm 50/50 DD and towing. I opted for a better towing experience. If I worked and drove empty most of the time I'd opt for the 3.55's.
    Or as in my case as well I drive a lot in the mtns of the PNW. Guess it boils down to your driving needs.

  8. #8
    Setting Up Camp
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    Quote Originally Posted by goducks14 View Post
    I had 4.10's on my Ram 6.4 Hemi. I specifically looked for 4.10 and 4.30 in Fords. I'm retired and my DD consists of short hops around town. DD mpg's don't matter much to me. I'm 50/50 DD and towing. I opted for a better towing experience. If I worked and drove empty most of the time I'd opt for the 3.55's.
    Or as in my case as well I drive a lot in the mtns of the PNW. Guess it boils down to your driving needs.
    Thanks. Sounds like based on my needs the 4.30 is not a must have.

  9. #9
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    My understanding is that 3.73<->4.3 ratio might result in 0.5-2.0 lifetime avg mpg difference for 7.3 gas engine... that for under 10k trailers its purely your choice... but that 4.3 gas ratio really revommended for safely handling 12k+ lb trailers with 7.3 engine going down steep grades as you have massive truck with large trailer and no diesel exhaust brake... there is a grey zone in the 9-12k range about 3.73 gear with 7.3 gas. And, I guess for 15k+ lb trailers, you'd be stupid to not buy 6.7 diesel engine... but ymmv.

    Sent from my SM-N986U1 using Tapatalk

  10. #10
    Long Hauler geotex1's Avatar
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    My takeaway is this is your daily driver and occasional tow vehicle. So gas and 3.55 make sense for the task and impact on wallet over the longer term. Just know and understand the limits on its performance towing. Braking is a legitimate concern, but can be addressed with a brake upgrade to the camper. Disc trailer brakes should really be standard in this day... My prior tow vehicle was an 8.1L gasser with 4.10s, before that a 7.4L gasser also with 4.10s so I understand!
    Rob & Nikki + Cloverfield
    2020 Grand Design Solitude S-Class 3350RL
    2015 RAM 3500 Longhorn Laramie Crew Cab, Long Bed, 4x4 Dually Cummins/AISIN

    Mountains of Pennsylvania

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