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terrible millege on my f550

Discussion in 'Ford Trucks' started by amars415, Sep 29, 2008.

  1. amars415

    amars415 Member
    Messages: 41

    I've got a 01 f 550 7.3l auto 2wd and I get between 6 and 7 mpg. IMO the gears are too low 4.88. It never runs in its peak torque rpm range, always reving too high. The tranny seems fine, no cat. converter, air filter good, new fuel filter, etc. This is what its been since Ive owned the truck, I would be thrilled to death with 10-12 mpg, what are you guys getting in your f550s with 7.3? any suggestions? I"ve already got it mildly chiped and no help. Thinking of re-gearing. thanks!
     
  2. JohnnyRoyale

    JohnnyRoyale 2000 Club Member
    Messages: 2,935

    Everything improved when I superchipped mine, and added K&N air filter. Its worth a try.
     
  3. 04superduty

    04superduty PlowSite.com Addict
    Messages: 1,354

    dont do a K&N sway on your truck, at least with diesels they are not recommended since they let to much junk thru.
     
  4. musclecarboy

    musclecarboy 2000 Club Member
    Messages: 2,303

    The 550's/5500's usually have 488's I'm pretty sure.

    How long have you had the truck? Has it always been like this? Odd to see under 10 on a 7.3.... maybe a new 6.4.
     
  5. Jay brown

    Jay brown PlowSite.com Addict
    Messages: 1,783

    that sounds about right for fuel mileage.... our 2000 model redlines at about 80 mph with the 4.88's.... it's nice to have the low gears though when your towing heavy... keep her at about 45 mph....lol
     
  6. Doakster

    Doakster Senior Member
    from Maine
    Messages: 650

    :dizzy: :nono: A no no to add on the 7.3
     
  7. Doakster

    Doakster Senior Member
    from Maine
    Messages: 650

    Has the truck always run well for you, any white/black smoke etc?
     
  8. JohnnyRoyale

    JohnnyRoyale 2000 Club Member
    Messages: 2,935

    Thats the first I heard. Why?
     
  9. Doakster

    Doakster Senior Member
    from Maine
    Messages: 650

    There are much better tuners out there than superchips that will make you're truck run better with lower egts, and the K&N is widely know for lack of filtration and making you're compressor wheel on your turbo look like someone put sand paper to it. But that's all for another topic/thread.
     
  10. TEX

    TEX Senior Member
    Messages: 606

    i would say its the 4.88's yes they are nice for towing and pulling around town but at high way speeds WOW. a lot of our fire trucks are F550 with the 4.88s and they get nothing for mpg. even a regear to a 4.30 something would help. i guess it comes down to where do you do most of your driving miles, hiway or in town?
     
  11. amars415

    amars415 Member
    Messages: 41

    I've had it since Dec of 06 and it has always run very well, no smoke, etc. And since I have owned it, I have had the same fuel economy.
     
  12. amars415

    amars415 Member
    Messages: 41

    I am thinking of re-gearing to a 3.73 maximum and I think a 4.10 minimum. I just got done driving an f350 drw with 3.73's and it had plenty of power pulling a load. Right now with the 4.88 going 55mph, I will slow down going up hills (fully loaded) because in my opinion, the engine doesn't have any torque at that rpm. And for those that are going to say that 3.73 are to high, just remember that alot of dodge drw trucks run with 3.55's, granted they have a lower torque rpm and I would never go that low on a 7.3 unless it was a commuter truck.

    engine rpm with stock gears @ 70mph: 2800 (redline @ 3200)
    engine rpm with 4.30 gears @ 70mph: 2467
    engine rpm with 4.10 gears @ 70mph:2352
    engine rpm with 3.91 gears @ 70mph:2243
    engine rpm with 3.73 gears @ 70mph:2140
     
  13. amars415

    amars415 Member
    Messages: 41

    most of my miles are in town and only a few times do I have to go more than a half hour drive even, but when they are longer drives I can watch that needle drop fast! You would think that it would get good millege in town because it doesn't have to work very hard to get rolling, but it doesn't matter if i'm in town or on the hwy.
     
  14. 04superduty

    04superduty PlowSite.com Addict
    Messages: 1,354

    have you looked into a gear vendor over drive unit? that way you keep your low gears for getting a heavy load moving, then have the higher ones for cruising.
     
  15. amars415

    amars415 Member
    Messages: 41

    yeah, i looked at gear vendors but its like 3000 dollars, i can buy alot of diesel for that much money and I could change the gears in the rear end 3 times. I really don't think i'm going to have a lack of power with 4.10 or 3.73 gears, i think with 4.88s you have so much unusable power anyways. literally, i could pull over a house... but there is no way to get enough traction for all that power.
     
  16. ducatirider944

    ducatirider944 Senior Member
    from Iowa
    Messages: 469

    3K is cheap that is only 750 gallons @ $4.00 a gallon. So if you jumped your milage to say 10-11 mpg or a 4 mpg increase that would only be 11500 miles at 6 mpg to 10 mpg or 13000 miles at 7 mpg to 11 mpg. After that it will be money in the bank. I bet an overdrive will cost more than 3K. I bet you would spend 1K just changing the rear ratio if you have it done by someone, 2K if it is a 4x4 truck. 4.10 would be a good combo ratio in my opionion
     
  17. Jay brown

    Jay brown PlowSite.com Addict
    Messages: 1,783

    we're grossing 39K with ours and the 4.88 is the perfect gear for the job, that's why i bought the truck....... really if ya think about it, a 550/5500 is designed for hauling and pullling, not for fuel conservation....i'd save the $3k on the gears and buy an old 2wd toyota and use it when your not pulling/hauling
     
    Last edited: Oct 3, 2008
  18. bribrius

    bribrius PlowSite.com Addict
    Messages: 1,609

    put taller tires on it.
     
  19. Jay brown

    Jay brown PlowSite.com Addict
    Messages: 1,783

    22.5's might fit..