K3500 Gearing

Discussion in 'Towing' started by oldbrown, Mar 8, 2020.

  1. oldbrown

    oldbrown Newbie

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    So we bought our 98 K3500 crew cab 454 dually to haul a camper. We ended getting a relatively small camper (25 ft, 4500 lbs empty). Just my luck someone swapped the 4.10 gears for 4.56 gears. Obviously overkill and poor mpg/high cruising rpm has limited its use to just hauling. I have finally decided to change gears. I am contemplating 3.73 gears instead of 4.10s. If it had 4.10s, I would leave it alone but since I need to change anyway, that’s why I am considering 3.73. Factory tow rating is 12k, 10k and 8k respectively based on gears. Truck has stock size tires, runs well and is in good mechanical shape. Anyone have my truck with 3.73s? Most I am sure have 4.10s. Even if I had to tow in drive with 3.73s in the hills, I think it may make the truck overall more user friendly. Thanks.
     
  2. Supercharged111

    Supercharged111 I'm Awesome

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    Do you have a pull and pay near you? That'd be cheaper than paying someone to regear yours. Then you could turn around and sell your 4.56 diffs. 4.10 was a very popular ratio. 3.73 was pretty popular, but not so much in the duallies and the dually rears are a little different than SRW. Just a thought.
     
  3. letitsnow

    letitsnow I'm Awesome

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    I'd use this as an excuse to put bigger tires on, and leave gearing as is.
     
  4. 454cid

    454cid Sooper Pooper

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    Mine are 4.10s, but are you sure the 4.56s are swapped and not original?
     
  5. b454rat

    b454rat I'm Awesome

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    I had a 97 with the 454/4l80/4.10s and towed great. Bumped tires up to 265s then 285s. If ur area is flat then I'd say 3.73s, if some hills then swap to 4.10s.
     
  6. Supercharged111

    Supercharged111 I'm Awesome

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    I like this idea better.
     
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  7. JavaMan

    JavaMan Newbie

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    I got a 96 K2500 burb 454 with the 3.73. I got the standard tire size, 245/75R16. It does great pulling our trailer, it's only 6500 pounds, but we have a lot of 4 to 6% grade hills here. If I keep it at 75 it'll stay in 4th gear. If traffic or speed limit slows us down below 70 then it likes 3rd.

    Sent from my SM-G965U using Tapatalk
     
  8. oldbrown

    oldbrown Newbie

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    Thanks guys. I was planning on just swapping front/rear axles from parts yard. My truck did come with 4.10 based on glovebox code. I appreciate all the feedback.
     
  9. stutaeng

    stutaeng I'm Awesome

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    The 4.10 were the standard gears for your truck with the 4.56 being an option. 3.73 were not available on the C/K 3500s in the 96-00 generation. I have a '00 K3500 SRW with 5.7 4.10s and really like them with LT265/75/R16s.

    I've considered going to 4.56s. Too bad mine is not a DRW, otherwise we could swap rear ends, LOL. Seriously, stick with 4.10s.

    If you do swap a 3.73 from yard, it will be from a C/K 2500, at least the 96-00. Make sure you get the full float, because the 2500 with 5.7 got the 14 bolt semi-floating, so look for a 7.4/6.5TD in that series. The front axle is the same for 2500/3500, so no worries there.

    Lastly, what gas mileage are you getting? The BBC is a gas guzzler. I'm not sure if there is a noticeable difference with changing gears. Someone may post similar truck/engine configuration and their MPG numbers.
     
    Last edited: Mar 9, 2020
  10. andy396

    andy396 GMT400 Enthusiast

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    I'll throw another vote in for the bigger tires idea!

    @BNielsen for another guy with 7.4L/3.73 but with 285's.

    Mine has a 7.4L/4.10 with 245's. In my opinion, towing 5000lb+ with hills, I wouldn't go any less.

    Empty, I'd love to drop the rpm's by another 25%. I like to dream about putting a Gear Vendors OD in it or somehow swapping in a 6L90E as a more optimal combination. I even found an RV salvage yard that has used Gear Vendors units for somewhere in the $1500-2000 range (I think?).

    If you do decide to swap out the 4.56's, let me know. When I go up to 285's I'd like to put 4.56's in.
     
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