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Factory Positraction

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by kiley, Jan 1, 2002.

  1. kiley

    kiley Registered Member

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    I was in snow today. When I bought my truck I was told I had positraction. Today proved that wrong. I only had two wheels with power. Does this mean I was lied to or is the factory posi just worn out?

    If it's worn out can it be fixed or replaced?
     
  2. Steve_Chin

    Steve_Chin 1/2 ton status

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    It could just have a worn out rear limited slip differential. If it is factory-installed, it'll be an Eaton unit with clutch packs in it. The clutch packs can be serviced. In order to be sure whether it has a limited slip differential or not, you will need to pull the cover. If it does not have a limited slip carrier in the housing, you can purchase one of a number of different types (clutch, cone, locker, air locker... Basically everything but a Torsen, which really would be the best LSD for a 4x4, but they don't make one for the GM 12-bolt).
     
  3. kiley

    kiley Registered Member

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    Thanks Steve.
     
  4. JIMs70K25

    JIMs70K25 1/2 ton status

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    I have a post like this on one of the other boards. I have a dana 60 with the Powr-Loc limited slip and was concerned about performance from a 32 year old unit. But that all got tested today with snow here southeast Va. To be certain, pull your rear cover off and see what's inside, the oil probably needs to be changed anyway. If it's not identifable post a picture I'm sure someone could identify it for you. Then explore your rebuild, replace or purchase options. Good luck..

    Stupid is as stupid does, I just try not to do anything stupid.
    <a target="_blank" href=http://community.webshots.com/user/70gmc>http://community.webshots.com/user/70gmc</a>
     
  5. alta-aj

    alta-aj Registered Member

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    Another posi question (maybe 2)

    I have a 72 Jimmy 2wd with a non-posi 3.73 rear end. I also have a 3.08 posi rear end from a 77 Blazer. I'm wondering if the carrier and all from the 3.08 will fit into the 72's differential housing. Otherwise the 72's spring saddles, etc will have to be transferred to the 77 rearend in order for it to fit the Jimmy. The emergency brake system (cabling) is different as well.

    The second part of the question is that if the gears will fit, will the 77's wider brake shoe system swap over as well? Now with the 400 installed I'd like to be able to stop 'er a little more effectively.
     
  6. Steve_Chin

    Steve_Chin 1/2 ton status

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    Re: Another posi question (maybe 2)

    The 3.73:1 ring gear will not fit on the 3.08:1 carrier because the 3.73:1 gear set requires a 3-series carrier and the 3.08:1 gear set uses a 2-series carrier. If both rears are GM 12-bolt truck rears, the gear sets and carriers will swap over as complete sets.

    WRT the brakes, bigger brakes won't stop a vehicle any better than ones that are just large enough to do the job. All they are capable of is rejecting heat at a faster rate, which makes them a little more consistent in stopping ability. Personally, I hate drum brakes with a passion and wouldn't contemplate a swap of this sort since I could just swap in a set of discs with just a little bit more labor and be done with it.
     

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