posi trac...

Discussion in 'GM Powertrain' started by Evil_E, Jan 13, 2010.

  1. Evil_E

    Evil_E Member

    so what would you recomend? now correct me if im wrong, but my truck is 3.42 gears right? i dont race my truck or anything like that but would love to change it up a bit. now besides the gears im more interested in posi trac. so what would you recomend? i just figured if im messing with that might aswell step it up on the gears aswell. any insight is appreciated. 3.55s or 3.73s...pros, cons?
  2. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    posi trac

    Theres not much differance between 3.42s and 3.55s. Id go with 3.73s, there a good compramize between economy and performance gears.
  3. MrShorty

    MrShorty Epic Member 5+ Years 1000 Posts

    There were a few different gear ratios installed in these, so it would be hard for any of us to simply tell you what gear ratio you have. Easiest way to find out (assuming you still have the factory installed gear ratio) is to look at your RPO code list in the glove box. Find any codes that start with G, then look those codes up on any of the available RPO code list databases (someone even posted one here once). While you're there, look for the G80 code, which is the RPO code for the factory "posi" that GM used in these trucks.

    If you do have an open differential in the rear and want to put something else in, it depends a lot on what you kind of "posi" you want: locker or limited slip. I see a lot of recommendations for an Eaton clutch type limited slip or Detroit's True-Trac geared limited slip for people (maybe like you?) who want something streetable but a little added traction under some conditions.

    2wd or 4wd? If 4wd and you decide to regear, recognize that you also need to regear the front.
  4. Badbrad469

    Badbrad469 Rockstar 100 Posts

    i had 3:42s in mine and went to 3:73s. didn't change the rpms too much on the freeway. i'm now turning about 2200 or so while doing 75. i'm wishing now that i would've went down to 4:11s because i didn't notice too much from the "seat of the pants" dyno. i also went with the detroit tru-trac unit and i couldn't be happier. my tires on the other hand, they could stand to be rotated lol
  5. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    Looks like a 2x i would say grab a rear out of 3:73 4x4 but i think you have five lug. might look into swapping you're five lug axle into that housing

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