Axle ratio's

Discussion in 'Trucks and Trailers' started by Travis Followell, Jul 16, 2005.

  1. Travis Followell

    Travis Followell LawnSite Silver Member
    from KY
    Posts: 2,207

    A friend of mine is getting ready to buy a new F-150 and they offer 3.55,3.73, and 4.10 non limited slip axle and they also offer them in limited slip. They come standard with a 3.55 non limited slip axle. Could someone please explain the differences in these different axles. Anything other than a 3.55 is $300 more.
     
  2. Albemarle Lawn

    Albemarle Lawn LawnSite Bronze Member
    Posts: 1,544

    Which does he want?

    If he's not towing very much weight (under 5,000 lb.) or not towing very often, get the 3.55

    If he's towing moderate weight (5,000-7500) get the 3.73, and retain some fuel savings over a 4.10.

    If he's towing heavy (7500-9500, or whatever is max for that truck) get the 4.10.

    If he's thinking of bigger tires, get the 4.10.


    The limited slip is a seperate issue, traction. It sends torque to the wheel with most traction, versus an open-differential which sends torque to the wheel with the least traction. Worth the cost if any driving offroad or in the snow is predicted.

    KB
     
  3. riches139

    riches139 LawnSite Senior Member
    Posts: 369

    The 4.10 is only available with the heavy suspension package, or 4x4.
    The 3.73 worked out good for me. :waving:
     
  4. Travis Followell

    Travis Followell LawnSite Silver Member
    from KY
    Posts: 2,207

    What would it do if you was to pull a heavy load with a 3.55?
     
  5. Tider6972

    Tider6972 LawnSite Senior Member
    from Alabama
    Posts: 649

    The lower gear (higher number) allows the engine to run at a higher RPM at a given road speed and, importantly, to gain RPM quicker when starting off.

    I other words, when you are driving 55 mph, the engine RPM will be higher with a 3.73 than with a 3.55, and evev higher with a 4.10. This higher engine speed lets the engine operate in it's power range, rather than 'lugging' at low RPM where it can't develop power.

    Starting from a standstill, the lower gear lets the engine rev quicker to it's power range and lets you get moving easier and quicker.

    Since the engine is running faster with lower gearing, it uses more fuel. "Lugging' (straining, or over working an engine at low RPM) will also cause an engine to use more fuel.
     
  6. Albemarle Lawn

    Albemarle Lawn LawnSite Bronze Member
    Posts: 1,544

    If you overload a 3.55 auto the trans can take up the slack but it will get hot.

    If you overload a 3.55 manual, and have to stop on a hill, you can really damage a clutch, in a smoky, stinky way.
     

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