Eaton posi or true track unit

Discussion in 'Transmission & Driveline Topics' started by RTSE, Apr 12, 2020.

  1. RTSE

    RTSE Member

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    New member with a 1978 Camaro 305 / TH350 & 10 bolt highway gears open diff. Car is in excellent condition with electric windows and A/C. I have decided it’s time for some upgrades, I have brought a 700R4 auto, I have a early 70’s 350 4 bolt mains steel crank, new alloy Dart heads, 1.6 roller rockers, solid lifter comp cam. Holley street dominator single plane manifold, Holley 750 HP double pumper and MSD ignition.
    First thing is to sort out the diff, I have new 3.42 gears and need to decide what is the better upgrade a Eaton posi unit or a Eaton true track unit.
    Thanks
     

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  2. big gear head

    big gear head Veteran Member

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    Either one will work well. I'm a fan of the Eaton Posi, but the Truetrac is very popular.
     
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  3. RTSE

    RTSE Member

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    Thanks for your input, I think either will work but the posi might be more user friendly
     
  4. badazz81z28

    badazz81z28 Veteran Member

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    Depends on what you are doing with the car? Personally....if this is a street car, maybe a trip to the track I would do an Eaton Posi. If this was mainly an autocross/road course car I would do the Tru-Trac. The Tru-Trac doesnt lock the tires up like Im used to with a posi. Its almost like you have to be going in a straight line for a sec to get it to become "posi" like.
     
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  5. big gear head

    big gear head Veteran Member

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    I agree, if you are going to be doing turns under power then the Truetrac would be better. Straight line stuff might be better with the Posi.
     
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  6. RTSE

    RTSE Member

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    Thanks for that, I am leaning towards the posi unit now
     
  7. 71RS/SS396

    71RS/SS396 Veteran Member

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    Rob, if yours is not locking until you get the car pointed straight, it's failing, that's what they do when they're on their last legs.
     
  8. badazz81z28

    badazz81z28 Veteran Member

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    Might be time for that upgrade!
     
  9. dave@ztech

    [email protected] Veteran Member Lifetime Gold Member

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    I do not think the true track has clutches and there for doesn't wear out , it puts traction to the tire that is not spinning , torque bias , and they are pretty strong correct maintenance makes it almost indestructible, great for the track and street , I would choose it over a true posi locker
     
  10. 71RS/SS396

    71RS/SS396 Veteran Member

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    They're far from indestructible, they wear out just like any other differential. The bias from the gears pushes against the case, it usually wears the case surface to the point that they lose their preload and then they don't put power down, they're not rebuildable. They're probably fine for the average guy putting around on the street, but if you regularly auto-x or road race they don't live.
    I've killed several of them in the last 5 years. Something has changed, either in their production process, or the material the case and or the gears are made out of. The first one I had in my car (2012) held up to abuse for a few years, after that the durability went down the tubes. Rumor has it that they started producing them offshore and that's when the quality starting suffering but I don't know that to be fact. There are better torsen style diffs out there that can be rebuilt, but of course they're more expensive and not in everyones budget.
    I'm with you on the locker, they don't work well if you want the car to turn, I tried one with the lightest available spring and it made the car understeer if you used any throttle in the corner. I've also tried a wavetrac, it didn't make it through the first weekend before it started slipping. I switched to a Larsen Racing Products Platinum drive this year, it's a billet case (vs cast) that uses a similar torsen design as the trutrac but it's rebuildable and has some tunability in its bias.
     

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