Mileage, gearing

Discussion in 'Trucks and Trailers' started by mstyles0927, Jan 31, 2001.

  1. mstyles0927

    mstyles0927 LawnSite Member
    from SC
    Messages: 32

    I had a 1976 1/2 ton 2WD LB AT truck with a factory 350 in it. When I wrecked it, I bought a 1980 1/2 ton 4WD SB MT truck with a used-up inline 6.

    When the inline 6 finally gave up the ghost, I pulled the 350 from the 76 and dropped it into the 4x4. I have rebuilt the carburetor myself with a kit from AutoZone(2 barrel), replaced the plugs and wires, checked the timing, etc (you know, a basic tune-up). I left the 4 spd manual tranny in the 4WD. Also, I know the 76 LB had a bigger gas tank (I think 18 or 20 gallon) than the 80 (16 gallon).
    But it seems like the 4x4 really drinks the gas much harder than the 2WD--I hit the station to refuel a lot. Is this common--I haven't made the time to pull the rear differential to look at the gear ratio, but this thing is really hitting the old wallet now?
    Last check on the highway trip to the lake I got just under 13mpg. In the city (with all the traffic and lights) it drops to around 11-12mpg.
    Any ideas out there?
  2. John DiMartino

    John DiMartino LawnSite Silver Member
    Messages: 2,555

    4x4's do use quite a bit more fuel than 2wds especially in older might have like a 3.73 in the 4x4 and had 3.08 in the 2wd,which will make it even worse than it should be.
  3. mike reeh

    mike reeh LawnSite Member
    Messages: 229

    man you get 13mpg!! i envy you :)

    a quadrajet or other 4bbl will wake up the motor at full throttle but say bye bye to gas mileage...

    like john said, its probably in the gearing, plus its a heavier truck. i definately know what you mean when you say its really hittin the old wallet.. :)

    good luck

    mike reeh
  4. 85w/350

    85w/350 LawnSite Member
    Messages: 244

    I also envy you I drive a 2wd sb GMC w/350 and it gets 10-1/2mpg in the city and 12mpg on the highway...i just mounted some 31 inch tires in hopes of helping my highway mileage by slowing down the RPM's a probably got worst I'll be filling up soon so i'll post another within the next few days
  5. Joseph Meidling

    Joseph Meidling LawnSite Member
    Messages: 44

    I will be looking for a 4wd, 1500 series to commute back and forth to work in. I was thinking about the 4.3L?? Any input would be appreciated. The commute is 30 miles each way.
  6. mstyles0927

    mstyles0927 LawnSite Member
    from SC
    Messages: 32

    Thanks for all the input. It seems like maybe I don't have it too bad, compared to some of you guys! I guess you have to give up the gas mileage for the privilege of driving one of the best trucks in the world!

    Thanks for all the input.
  7. Mowman

    Mowman LawnSite Senior Member
    Messages: 553

    Yes, 25 MPG pulling my trailer and equipment. I bought this truck new (ordered) it in 1998. I wasn't mowing much then and wanted the best MPG. S-10 w/ 2.2 Vortec 4 w/5 speed trans. I'm now pulling a 5x10 open trailer w/ Walker mower and misc. equipment, about 1900lbs. It handles it fine. Next truck will have a 4.3 V-6 and auto w/ 4X4 for snow removal. But hey for now it's getting the job done.
    And I'm whining at 25, don't know how you guys do it, 8-12 MPG?
  8. 85w/350

    85w/350 LawnSite Member
    Messages: 244

    If you are complainig about 25mpg somethig is wrong...I see you also have a 4cylinder compared to our 8's...the 4.3 is a good little engine and I have seen up to 30mpg out of one in an s-10, but it was highway mileage, not a 4x4 and definately not pulling a 19,000lb a days if you can even find a chevy truck much less any truck (I'm talking real trucks 1/2tons and bigger) that can get 25mpg you found yourself a deal....

    In my opinion sometimes you have to give up the mileage for power and for driving a dependable truck that will run practically twice as long as any other mileage is bad and i wish it were better and i am going to change the gearing soon hopefully to 3.08's from 3.73's...

  9. roland26

    roland26 LawnSite Member
    Messages: 16

    my 84 gmc has a 350/300 gm crate engine with hedders,edelbrock manifold and quad jet. it has a 700 with 28" tires. with the 308 gear it runs about 2000 rpm at 65.
    and it get 13mpg. but according to the vac gage I am in the
    carb alot.I think my final gear is 2.10 (in od) and that is toooo high. I am going to 3.42 (mabe a 3.73) and mabe I want be in the carb so deep. with the 3.42 I think the final drive will be about 2.60 and the 3.73 about 2.80. do these figures look correct. I dont expect 17 to 18 mpg but 14 to 15 would be nice. roland
  10. 85w/350

    85w/350 LawnSite Member
    Messages: 244

    I heard that the 3.42 with the 700 tranny is a nice setup as far as gearing and gas far as the numbers i'm really not sure

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