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  1. #1
    Setting Up Camp
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    New Rearend or Not

    Currently towing a Transcend 265BH with a 2009
    Suburban 6.0 and 373 rearend.. It has 129k and Iím scared
    and wanting to rebuild the engine and trans early in case
    parts become unavailable..
    Have had no trouble towing across the US except in some areas in Wyoming and Colorado were it strains at times on the long grades.
    Yes would love to Duramax it but donít want to pay 33k for that.
    So if I rebuild will there really be that much of a difference in towing with a 410 rear verses 373..
    Iím aware the gas mileage will decrease with the 410.

    And does anyone have ideas on a computer that would help with the 373 preform better..
    Thanks for your info

  2. #2
    Long Hauler
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    Your 6.0 engine is a cast iron LS engine, and it's known for its long lifespan and reliability. You might be warranted to rebuilding your engine--about 2030. It's a 300,000+ mile engine if maintained properly.

    Don't worry about parts availability as engine and running gear parts are readily available in every auto salvage yard.

    You should change fluids from time to time in the tranny and the rear axle. But otherwise you should be good to go. The 3.73 is the most popular gear ratio for all uses. And your trailer doesn't push the axle's capabilities.

    You could put a tune on your truck, but it wouldn't do that much--other than make you use "high test" fuel. Tunes do best on supercharged or turbocharged vehicles--like diesels.

  3. #3
    Setting Up Camp
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    Thanks for info.. This truck is over serviced . Every year all fluids flushed and it only gets around 18k of miles of use 7k of that from trips out west..
    Plan on extra large transmission cooler and new air intake very soon as well as normal maintenance as usual..
    thanks again

  4. #4
    Long Hauler D2Reid's Avatar
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    One of the reasons I chose the F450 over the F350 was the rear differential ratio, 430. While bouncing ideas around in the forums naysayers told me that I would get less fuel mileage, and it's true, 1-2 gpm less. But another huge factor in the equation is that I don't drive fast. I pull at 60mph. 95% of unhitched driving is on rural roads, 55-65 mph speed limit.

    What I love about the F450 with 430 rear end is that when I start up 7-8% grades it hauls my 20k 5th wheel up those hills without strain. I think there are more folks that pull on fairly flat roads at high speed than there are folks that pull over steep hills at slower speeds, of course they think the 373 is the best rear end. So while I may be the odd man out, I will keep my 430 rear end.
    Dallas
    2017 Momentum 376TH, 2019 Ford F450, Dual Rear Wheel, 4x4, diesel.
    2015 Harley-Davidson Street, XG750

  5. #5
    Seasoned Camper That 1 Ron's Avatar
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    I wouldn’t worry at all about parts becoming unavailable for your suburban. The 6.0/6L90 trans combo is one of the best out there still to this day. Not only does GM still offer a full line of OEM replacement parts, the aftermarket has really catered to this combination as well. Unless you’re having issues with the transmission or engine, I wouldn’t worry about rebuilding them with that mileage. As far as re-gearing the differential, 4.10 gears will help a little by keeping the engine more in its powerband but it won’t be earth shattering different. It probably won’t even affect the mpg and in some cases, may even help achieve better mpg. 4.30 or 4.56 gears will be better for towing and you’ll feel a bigger difference but will most likely negatively affect the overall mpg. 4.10 gears were a factory option so you might be able to find a complete differential at the salvage yard. Look for GT5 on the build tag, usually on the glovebox door (your suburban should have GT4 on this tag). Is your suburban 4x4? If so, you’ll need to re-gear the front differential as well.

    As for computer tuning, the factory tune is conservative. An aftermarket tune can help wring a few more ponies out of the engine and adjust the shift points and line pressure so you feel the difference. An aftermarket tune will also help you get the most out of an aftermarket cold air intake. In naturally aspirated engines, the difference won’t be huge like turbo gas and Diesel engines. There are a lot of options for your suburban in the aftermarket world. Not sure where you’re located but I’ll bet there’s someone close that offers custom tuning for your 6.0. A word of caution, not all of these tuners are good or know what they’re doing. There’s also handheld tuners available that you plug in, and reflash your vehicle yourself. You can also remove the custom tune and reflash to stock anytime with these and some allow you to read engine codes. I would recommend talking with 5 Star Tuning if you’re thinking about it. As for aftermarket air filter (cold air intake), I like S&B the best and AFE second.
    2020 Grand Design Imagine 2400BH
    2017 Toyota Tundra TRD Pro Double cab

  6. #6
    Seasoned Camper
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    Quote Originally Posted by Rolltide1 View Post

    And does anyone have ideas on a computer that would help with the 373 perform better? Thanks for your info.
    How about this?

    https://whipplesuperchargers.com/ind...&product_id=21

    Real game-changer and a lot cheaper than a diesel conversion!
    2023 Reflection 315RLTS
    2017 Ford F-350 Crew Cab Short Bed SRW, 6.7L Diesel
    Hensley Swift Arrow

  7. #7
    Setting Up Camp
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    Thanks for all the info… will probably do the oversized trans cooler and new diff ribbed cover for right now… Also I’ll look into the tuner for extra control..
    That turbo looks fun though!!!
    Thanks again

  8. #8
    Long Hauler
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    Quote Originally Posted by Najataagihe View Post
    How about this?
    https://whipplesuperchargers.com/ind...&product_id=21
    Real game-changer and a lot cheaper than a diesel conversion!
    Would that make you get gallons per mile instead of miles per gallon?

  9. #9
    Seasoned Camper
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    If you keep your foot out of it, it gets BETTER mileage, because of the increased efficiency of the fuel burn.


    If you just can't resist burning rubber...

    Well, at that point, your tire cost is what becomes prohibitive.

    2023 Reflection 315RLTS
    2017 Ford F-350 Crew Cab Short Bed SRW, 6.7L Diesel
    Hensley Swift Arrow

  10. #10
    Site Sponsor
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    Banks has a good video on rear dif covers. Talks about the fluid actually flows in the dif, and importance of properly designed covers. 5 star is great. Tunes are solid and safe, and customer service is top notch.
    2021 GD 31MB; 2022 F350 Rapid Red, Lariat Ultimate Package, CCSB, 4x4, 6.7 Powerstroke, B&W 20K Patriot slider

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