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285 70 17 tires & 4.10 gears

Discussion in '7.3L Powerstroke Diesels' started by Dragrace504, Nov 4, 2019.

  1. Dragrace504

    Dragrace504 Registered User

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    I just switched to 285 70 17 on my 97 f250 powerstroke,it's 2wd single axle and has 3.55 gears.seems like fuel mileage went down a bunch and little loss in take off power,you guys think 4.10's would be ok I drive daily and tow some
     
  2. DaveBen

    DaveBen Supporting Member Supporting Member

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    I would not drop that much. I would think 3.73 gears would work. You don't want to go to the other extreme; screaming down the freeways.
     
  3. Dragrace504

    Dragrace504 Registered User

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    Yeah you maybe right,I brought the 4.10 awhile back had them laying around. I might see if someone wants to 3.73 for these 4.10
     
  4. greenskeeper

    greenskeeper Full Access Member

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    Larger wheels/tires take more power to spin from a stop. However, I'd keep the 3.55 and just run out of O/D when towing. I purposely searched from non-4.10 trucks when I bought the two that I have due to the 4.10s guzzling fuel and screaming rpms on the highway
     
  5. u2slow

    u2slow Plan B

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    I assume auto trans? Mileage... towing/empty? highway/city?

    I experienced similar going from stock tires to 33" on my PSD E350. I compensated with a deep alum trans pan, and by stepping on it harder. :D Trans temp gauge was next, but didn't happen. Researching tuners suggested some tunes optimized the trans shifting.

    My PSD F350 (5spd) with 4.10's felt better after going to 34-35" tires.

    I caution about the 3.55 to 3.73 switch. You're only going ~1/3 of the way toward 4.10, not halfway. (3.92ish is the missing step). The cost to re-gear for such a slight change usually doesn't make sense. But if you've got other axle work to do anyway, it'll save on your labour.
     
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  6. Dragrace504

    Dragrace504 Registered User

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    Yeah it's an automatic, I haven't really recorded fuel mileage I'm going by fuel gauge and feel.The rpm's and looks are great now but wish I could better fuel mileage. I agree it would probably be great if they made a 3.90 gear.
     
  7. fraree

    fraree Full Access Member

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    Funny, fuel economy & big truck! Heaps of non F series owners say to me " you'd be luck to get from one bowser to the next" The 1 ton Toyota land cruisers 4wd, which are the norm out here, run a 4.5 litre V8 turbo diesel & chew 35-40 % more fuel than my 7.3 PSD unladen than mine does towing a 3 tonne caravan (travel trailer).
     

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