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  1. #1

    Default new gears necessary?

    I have the 3.73 posi rear end in my truck, and want to go from 33" tires to 35" tires at the next time they are due. Do I need to put new gears in the rear end? I have heard 4.10 or 4.56. Which would be better? Also, do I need to change the front differential gears as well, if possible?


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  2. #2


    If your upgrading to 35's then you really should do the gears. And you will need to do front and rear otherwise it will just bind and break everything. I would probably do 4.56 because then if you ever want to put on tires bigger than 35's you don't need to worry about buying gears a second time.
    1999 GMC Sierra 2500 350 vortec
    1967 Jeep M725 ambulance 230 tornado
    1990 Cherokee Limited- 3 inch lift on 33's
    ...and every one of em has issues

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  3. #3


    i would go with exactly what dan said... go 4.56's and you will need to do the front too
    95 GMC Sierra 2500
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    1999 Jeep Cherokee, 3" Rustys lift, 33" BFG MT's, locked, armored: Rolled :(
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  4. #4

    dwill3015's Avatar
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    Jan 2007
    Yacolt, Washington
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    X2-what he said!
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  5. #5
    finalday7's Avatar
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    Oct 2007
    Sayward, B.C Canada


    If 500-800 bucks isn't in the budget right now then you don't HAVE to change them right away. A change in the near future would be a safe bet.

    2007 GMC Sierra CrewCab 4.8L
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  6. #6


    $500-800 installed or just for the parts? Dad's a heavy equipment mechanic, and he has helped me with most of the stuff for the truck, but he has only done two rear ends in a pickup in his 30+ years as mechanic. Does it in cranes all the time, but very rarely a truck. How difficult is it to install the gears ourselves, or is it best to have a garage/shop do it for me?


  7. #7


    If dads a Heavy Eqpt. Mech. with a gear change or two under his belt he should be able to tackle this job with you. Plan for a whole day of work to do both diffs.
    Remove one gear set at a time, swap the gears, trial fit and shim as required. Probably want to replace the axle seals at the same time (cheap insurance). When purchasing the gears buy a master install kit (axle seals wont be included and will need to be purchased separately), and a gallon of your favorite diff. lube.
    I'd recommend 4.56's for 35" tires.
    $500 to $800 sounds like parts only for both diffs, install with parts is usually closer to $1100-$1200

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