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regear 78 trailer special blazer for mpg

Discussion in 'Chevy Trucks' started by bullwinkle, Feb 9, 2002.

  1. bullwinkle

    bullwinkle Junior Member
    Messages: 3

    I have a 78 Blazer, 4wd, automatic with a 350. It is equiped as a trailering special with 4.10 gears front and rear and gets roughly 8 to 10 mpg at 55 mph. I want to gear it up to gain better gas mileage and was wanting to know if anyone has done a similar gear swap and what kind of results they gained? Load pulling ability is not an issue since I don't have anything to pull anyhow. Thanks for any input.
  2. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    To regear that truck,with it being a 78,may not be worth the money.Its going to cost you over 1000 dollars if you have someone do the work.I had a K blazer with 3.42 gears,it never got more that 12 on the highway.it would take a long time to your money back,and you'd lose accelration power,If you needed new tires id get the tallest ones you couls fit,this will help the gearing for about 1/2 the money of the gear change.
  3. Chuck Smith

    Chuck Smith 2000 Club Member
    from NJ
    Messages: 2,317

    I own two GM trucks (one a 77, and the other an 80) and both have 4.11 gears. One has 33" tires, and the other has 36" tires. Guess what? They both get between 9 & 12 MPG on average. Stock tire size on a 3/4 ton is about 31" tall. The 77 I actually got 17 MPG for a trip I took a few years back. All highway, and all flat. I was amazed. I have spoken to people with 2.56 gears, and their mileage isn't much better than the 9 - 12 we all seem to get.

    I know in the hands of an uneducated driver results could be disasterous, but one day I would like to see split rear ends in HD pickups. Couple that with overdrive, and you have serious pulling power, and decent mileage.

    Then again, I suppose the split rear could be computer controlled.

  4. MTCK

    MTCK Senior Member
    Messages: 346

    I assume it has the full time 203 case. Converting to part time might get you a MPG or two. Then slap on some nice skinny tall tires, and keep your foot out of it, and I'd say that's your best bet. You're just not going to see the improvement that would make it worth the money to do that. Say you go from 9 mpg to 12, and the gear change would cost you 1000 dollars, and gas cost a dollar a gallon, just to make the math easy: you would have to drive 36,000 miles to make it worth your while. at 12 mpg that would be 3,000 gallons of fuel, and at 9 mpg that would be 4,000 gallons, $1000 difference.
  5. Power mad

    Power mad Member
    from Oregon
    Messages: 75

    I drive my K5 with 4:10, 3/4 ton axles 104 miles every day to work.
    33" tires.
    I figure that am getting almost 13mpg and that is doing 70MPH almost the whole way.
  6. bullwinkle

    bullwinkle Junior Member
    Messages: 3

    Thanks for the info guys, it's given me a little more insight as to the sensability of changing gears. The blazer is in very good shape looks wise and is getting very near to being a very sound runner. Not a bad rig considering it's entire life has been spent in interior Alaska running the highway (unpaved) between Manley and Fairbanks, the thing had 1/4" dirt between the roof layers when I put in the sun roof. Anyhow, I plan on keeping it going for a long time and maybe doing an interior restoration and body rust clean up in a couple years. Thanks again.
  7. MTCK

    MTCK Senior Member
    Messages: 346

    How does the maintenance fair on a rig up there in the interior? I'll be transfering to UAF next fall and want to take my 83 up there with me, but am kinda nervous about how it will handle the winter. Also do they give you smog checks up there? Visuals only or actually put it on a machine? Either way I may be better off driving something else as I wouldn't pass the visual. Thanks

  8. bullwinkle

    bullwinkle Junior Member
    Messages: 3

    Winters up here have been getting warmer over the last ten years (global warming?). You used to be able to count on a couple of -40F (daytime high) cold spells every year that might last a week or two, but the last two years in particular have been far warmer than I can ever remember. We have seen short, day long cold snaps of maybe -35 but on average it has been -15 at night and +10 during the day. However, better be prepared for the cold. Get an oil pan heater and block coolant heater, Mandatory, no if's and's or but's........ Your dead in the water without them. Run both to a common three way short (foot long) extension cord (leave the third recep for battery charging, trouble light etc,,) and tie wrap the cord so the end sticks out of the grill area near the bumper, easy to get to but out of the way otherwise. Make sure your anti freeze is set to -50F, Seriously it might get that cold and at the risk of sounding macho we do not stop for the cold. If you plan on getting a job off campus be prepared to drive to it regardless of the temp. Make sure all your belts are new and tight at the begining of winter, get a good average brand name and you wont have any troubles. Look into running full synthetic oil in the motor, not mandatory but it helps. Also check into synthetic in the differentials, T-case and transmission, again, not required but it wouldn't hurt. Make sure you have a good battery and good clean connections and most importantly get a good heavy duty set of jumper cables and NEVER take them out of your truck further than they will reach. Some people say you need a battery blanket heater, I have never needed one, most people don't, but it wouldn't hurt to get one if you want it (use the third prong on the splitter cord). Make sure you have a good, inflated spare tire and any tools you need to change it with. Last but not least, Get a good 20 foot long extension cord and also get an in line light you can plug in between the cord and the three way. Spend the extra money to get a good heavy guage wire and a -50 below rating on the outer jacket, you may have to search a little or go to an industrial type shop to find it but get a good cord that will flex in the cold and always leave it in your'e rig if you aren't plugged in. There is a lot to know, especially if you haven't lived in a colder climate before. I'll send you my e-mail address if you have any more questions. We are required to have our vehicles get an emissions check, tail pipe probe and everything, before we can renew our registration. You would need to call the DMV State Trooper office in Fairbanks to get the specifics on an out of state registration. Fairbanks sits in an area that is more or less windless most of the time so we get some bad air, especially when we get a cold temp inversion going. Well enough said, I hope the little bit of cold advice has helped you and anyone else that might have read this.
  9. MTCK

    MTCK Senior Member
    Messages: 346

    Thanks for the info, wrote you an email.....