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Thread: Need a quicky lesson

  1. #1
    Looking to get a new F250/350 4x4 w/6.0. Probably a 5-6 inch lift. I anticipate some performance upgrades in the future as well, chip, exhaust etc. Question is......
    What are the best rear end and tire size combo's?
    For example 373 gears and 37's or whatever. Give me the pro's con's of various combos such as towing capacity, acceleration off the line etc.
    The heaviest thing I'll tow regularly is my 21ft Ultra or maybe a fifth wheel down the line.
    Thanks in advance

  2. #2
    You should be fine w/ 37's and 373's.
    Ask Jackpunx, as he just lifted his 6.0 f-250.

  3. #3
    no problem towing your boat or a travel trailer,all you need is a drop hitch. But if you are going to tow a 5th wheel possibly in the future, with a 5"-6" lift you might run into clearance problems. What I mean is from the top of your bed rail on the truck to the bottom of the trailer extending over the bed. It can be done, but is going to cost some coin. You might just be able to get away with flipping the trailer axles. anyways, just something to think about down the road. I have an f-350 cc, lb 4x4 6" lift, 36" parnelli jone dirt grips, with the same issues.
    My truck has the 3.73 stock axle ratio, and I can feel the diff over the factory tire combo, also your speedo is going to need recalibrated, if you want it to read properly.

  4. #4
    Thanks CrazyHippy and H2obug. Yeah, I knew about the clearance issues and I'll deal with that when the time comes. I guess a more specific question woulda been......
    What can I expect if I change gearing and tire sizes. What does what to what ,ie, taller/shorter gears and tires vs 373's and 37's regarding acceleration, mileage, towing etc.
    Thanks again fellas

  5. #5
    Dragboat Dad
    I stuck with a 4' lift because of the 5th wheel, I didn't want to go any bigger then 315's because of the load I wanted to pull. Had to flip the axles to level the 5th wheel, it's still not totally level but I think I will put bigger tires on the 5th wheel to get it level.

  6. #6
    Going to 410's will help w/ acceleration, and will get you moving easier while towing. It will KILL your wallet though (at least on stock size tires). 410's and 37's Mathmatically is the very similar to 33's and 373's, so..... I dont know.

  7. #7
    That's kinda what I was getting at. Thanks.

  8. #8
    Right now I’m on 37's with 373's .. If you can get 410's it will be a great match. I dont know what the MPH will be though.. I added the quadzilla.. It will smoke the my PJs at about 15 MPH.. As far as off the line.. I don’t feel much difference.. Your not going to have a quick off the line feel with a diesel regardless of tire size.. But defiantly not a lack of power either. I did a couple of other things (intake and exhaust) But I don’t think its a necessary thing. The only thing that bumms me out .. (just a little) is they only calibrated my tire size back to 35's .. So My MPG is off .. I would love to know exactly what Im getting.. I can tell you that with my 3400LB boat and tires.. I towed from Havasu.. When I got back to LA.. I still had a little less then a 1/2 tank.. I think Im getting around 16-18 on the highway.. That gear and tire size will bring your RPM's lower at a higher speed.. The extra power will keep your momentum.. Hence 1 or 2 more MPG.
    Good luck.. I’m stoked with mine.. If you have any questions.. PM me

  9. #9
    Go lower numerically higher like 4;56 or 4:88 it will be very close to stock plus with the overdrives in modern trucks u wont lose anything on the highway, but it will still pull hard of the line cuase your gonna feel 37's with stock gearing of the line and on hills. My buddy runs 40's on a stock 6.0 no motor mods and it will roast them off the line with 4:56's but has only a 50 rpm drop at cruizing. plus with that big of tire and stock gears they tend to hunt in and out of overdrive becuase of the drop in rpms. just my 2 cents

  10. #10
    35's on a Duramax with a hypertech and no gear change. It'll smoke the tires and put your head back.

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