Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

MPG loss from switching to 14bolt?

Discussion in 'The Garage' started by moturbopar, Nov 19, 2005.

  1. moturbopar

    moturbopar 1/2 ton status

    Joined:
    Feb 9, 2005
    Posts:
    387
    Likes Received:
    0
    Location:
    mesa az
    HI I was wonderin how much fuel miliage you guys have lost switching to a 14bolt axle compared to the 10 bolt/12bolts?
     
  2. xpndbl3

    xpndbl3 1/2 ton status

    Joined:
    Jul 30, 2005
    Posts:
    510
    Likes Received:
    0
    Location:
    orland park, IL
    shouldn't really be that large of a loss. typically we change gearing at the same time, so who knows how that would affect it. personally i went from 3.73 to 4.56 gears, so that alone would change mileage
     
  3. mechted

    mechted 1 ton status Premium Member

    Joined:
    Oct 19, 2003
    Posts:
    765
    Likes Received:
    2
    Location:
    Granbury, TX
    if you get the same gears, and the same diameter tires then you are basically adding 150-200 lbs of wieght, but essentially nothing else will change
    just think of it as having a passenger along for the ride

    you could get into arguments about rolling resistance of a 14b vs. a 10 bolt...
    you could also get into arguments about the added aero-drag of the 14 bolt...
    but effects are negligable
     
  4. B_to_C

    B_to_C 1/2 ton status Author

    Joined:
    Jan 15, 2003
    Posts:
    1,861
    Likes Received:
    1
    Location:
    In Government Housing
    Yea, I went from 3.42 to 4.56 so I couldn't check for a long time. But I know now (using GPS) that I get what I was supposed to out of the factory...about 12mpg
     
  5. 4xcrazy

    4xcrazy 3/4 ton status

    Joined:
    Oct 31, 2003
    Posts:
    9,471
    Likes Received:
    5
    Location:
    Olympia/Lacey, Washington
    i lost about 5 mpg,,,


    then again it could be the combo of the lift, bigger tires, heavier drivetrain, and my fatass getting fatter :doah:

    and also my gearing went from 3.42's to the 4.11's in it now
     
  6. diesel4me

    diesel4me 1 ton status Premium Member

    Joined:
    Jul 24, 2003
    Posts:
    17,534
    Likes Received:
    920
    Location:
    Massachussetts
    Might get better!

    I've seen a few trucks that had 2.73's,2.56 or 3.08's 1/2 ton axles actually get 2-4 MORE miles per gallon when 3/4 ton axles with 4.10's or 4.56's were installed,due to the gearing being better suited to the big tires they wanted to run (36")...kept the motor from lugging,and in its best power/torque band..this is not always true in highway driving though.. :crazy:
     
  7. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

    Joined:
    Dec 14, 2001
    Posts:
    22,059
    Likes Received:
    69
    Location:
    Pleasanton, CA.
    The only way you're going to convince me you LOST 5mpg is if you show us where you had your speedo re-calibrated AFTER you swapped axles and axle ratio. Once you change tire size or gear ratio you cannot calculate fuel mileage using the odometer until you've had it re-calibrated.
     
  8. beater_k20

    beater_k20 Banned

    Joined:
    Dec 9, 2003
    Posts:
    10,276
    Likes Received:
    0
    Location:
    Elkhart, IN
    wouldnt the 14 bolt actually be more efficient, since the axle shafts do not support the weight of the vehicle, thus making them easier to turn? :dunno:

    aero drag on a rear end housing? :screwy:
     
  9. 4xcrazy

    4xcrazy 3/4 ton status

    Joined:
    Oct 31, 2003
    Posts:
    9,471
    Likes Received:
    5
    Location:
    Olympia/Lacey, Washington
    i'm really only guessing, but with the known mileage to work, and the amount of fuel used, i am getting around 10,,,maybe 12 mpg.

    and the recent trip to SoCal just about killed me on fuel as well :doah:
     
  10. mechted

    mechted 1 ton status Premium Member

    Joined:
    Oct 19, 2003
    Posts:
    765
    Likes Received:
    2
    Location:
    Granbury, TX
    i said the effects are negligable
    im working on a lab report involving aero drag on an airfoil, comparing it to drag of a cylinder... so i kinda extrapolated, sorry :D
     
  11. resurrected_jimmy

    resurrected_jimmy 1/2 ton status

    Joined:
    May 23, 2005
    Posts:
    2,241
    Likes Received:
    0
    Location:
    back home in Houston
    My gas milage went up when I did my 14 bolt swap, or maybe that was just the fact that it could move under its own power again instead of sitting on jackstands with a grenaded 12 bolt for the 3rd time
     
  12. 4xcrazy

    4xcrazy 3/4 ton status

    Joined:
    Oct 31, 2003
    Posts:
    9,471
    Likes Received:
    5
    Location:
    Olympia/Lacey, Washington
    the other thing, i believe the only reason my fuel mileage went down is mainly from the gears, going from 3.42 to 4.11 was a little bit of a jump.

    maybe alittle more areo drag from the lift i dunno.
     
  13. beater_k20

    beater_k20 Banned

    Joined:
    Dec 9, 2003
    Posts:
    10,276
    Likes Received:
    0
    Location:
    Elkhart, IN
    you have 4.10s, 35s, and overdrive. that gearing is VERY close to where your Blazer would be stock. there's absolutely no reason to lose fuel economy by that much. did your driving style change at the same time?
     
  14. 4xcrazy

    4xcrazy 3/4 ton status

    Joined:
    Oct 31, 2003
    Posts:
    9,471
    Likes Received:
    5
    Location:
    Olympia/Lacey, Washington

    yeah i do now, just recently got the tires, and for quite some time, when i first got the 14bff with the 3.73's i was still running tires at 31".
    then gear changes to 4.10's and 33"tires did alittle more, and now with 35"BFG's...it's coming around

    the mileage has changed some with these new larger tires, just haven't figured it out yet, JUST got them last week :D
     
  15. muddybuddy

    muddybuddy 3/4 ton status

    Joined:
    Jan 29, 2004
    Posts:
    8,933
    Likes Received:
    1
    Location:
    Fairfax Station VA
    i was gettin around 10 or 11 with 3.73s and 35s with the 10b's. i now have 5.13s in a 14b, but its still not completely together yet. milage should be interesting until i get the 40s :D
     
  16. 89GMCSuburban

    89GMCSuburban 1/2 ton status

    Joined:
    Nov 15, 2001
    Posts:
    3,005
    Likes Received:
    0
    Location:
    Thornton, CO
    Uhh, he added a lift, driveline, and bigger tires. You can't expect to gain something like 5" of tire, 4" of lift and heavier driveline and have it NOT lower mileage. With 3.42's and 31's I'd get 14, with 36's and 4.10's (adjusted speedo as well) I get 8.
     
  17. 4xcrazy

    4xcrazy 3/4 ton status

    Joined:
    Oct 31, 2003
    Posts:
    9,471
    Likes Received:
    5
    Location:
    Olympia/Lacey, Washington
    this is basically what has happened, only i didn't figure 8, i was figuring somewhere around 10, maybe 12 depending on how light on the foot i was,,,but with gas prices the way they are,,,,YES, my driving style HAS changed,,,VERY easy on the go-pedal :D
     
  18. blackblazer717

    blackblazer717 1/2 ton status

    Joined:
    Jul 1, 2004
    Posts:
    470
    Likes Received:
    0
    Location:
    massachusetts
    i lost about 4 or 5 miles to the gallon

    LUKE
     

Share This Page