93 Chevy 3500 Dually Ring and pinion change questions

Discussion in 'Chevy C/K Truck Forum' started by rdc500, Oct 25, 2011.

  1. rdc500

    rdc500 New Member

    I have a 1993 Chevy 3500 Dually, the truck is lowared. My problem is I get about 10 miles per gallon. This truck is never going to pull a heavy trailer. It has a 4.11 gear in it now, I want to put a 3.73 or lower to bring down the rpms. I know the speed-o will be off, what can I do to fix that, and can a ring and pinion be put in my current housing? My truck has a 454, with overdrive. Thanks Ron
  2. Boonduff

    Boonduff Rockstar 4 Years 100 Posts

    Yes, you can keep your current housing and just change the gears, but I wouldnt expect a huge increase in fuel mileage. I'd think you'll probably see an inprovement of maybe 1 to 2 mpg. If you look at the mileage ratings of new trucks the ones with 3.42 gears are only getting 1 mpg better then the ones with 3.73s. The 454 is a thirsty beast, and has alot of truck to move. I'd look at the cost versus benefit ratio before performing the swap.
  3. rdc500

    rdc500 New Member

    Thanks for the quick response, I do a fair amount of highway driving, at 70mph near 3000 rpms, the truck is balanced well and I like 80mph but the motor sounds like a NASCAR at 80. So I want to bring down the RPM's. Now if I do this my speed-o will be off how do I fix that?
  4. Boonduff

    Boonduff Rockstar 4 Years 100 Posts

    There are several ways to correct your speedo depending if yours is electronic or mechanical. I'm not sure what year GM switched from mechanical to electronic. Pre-OBD2 vehicles with electronic sppedos usually use a converter that wires inline. Mechanical fixes usually involve swapping a small gear in the tailhousing of the transmission on 2wds and transfercase on 4x4s. I'd find a 4x4 shop near you and talk to them. They deal with it all the time when lifting trucks and putting on bigger tires.
  5. rdc500

    rdc500 New Member

    Ok, thanks for the advise. I will do what you say.
  6. outalne94z71

    outalne94z71 Member

    all gmt 400 trucks had electric speedo, you can modify the drac unit easily to make it adjustable for gear/tire changes, there is a writeup at tbichips.com for that

    as far as gear change, its not all that bad on that 10.5 rear but with that tire mass of a dually you would be better off with staying 4:10 and swapping in a gear vendors overdrive unit to help with those highway speeds, 10mpg actually is decent for a 454 in a dually, our c3500hd with a 454 gets only 5.5 mpg
  7. mthomas

    mthomas Rockstar

    seems you might not like what it will take to get that bad boy moving. (more gas pedal)

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