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Diffs, FAQ

Discussion in 'V6 Development And Modification' started by immortality, Apr 2, 2008.

  1. HSV08

    HSV08 Member

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    does that include the pinion gear aswell? I have to confirm my diff as I think I have both a 78 in car (which lsd is not the greatest and a vt supacharged 6 diff, which I think maybe a 3.07?) was planning on dumping the lsd out of the s/c diff and throwing it in my diff in car and getting rid of the old diff but want to swap in a new set of gears aswell.



     
  2. HSV08

    HSV08 Member

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    The diff is a 3.07 from the s/c and my orginal diff in car should be a 3.08 right? so ones a 78 and ones a 80, but both have 4 bolt flanges not donut flanges
     
  3. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    Yeah, crown wheel and pinion, they are machined as a set so you should never separate or mix sets unless you want a really noisy diff that won't last long.

    What model VT? 3.07 standard diff ratio would indicate that it's a BW80 diff so you would be looking for some 3.46 gears (standard in VT series 2 onward LS V8 with T56 manual trans).

    The factory LSD can be rebuilt, depending on where you are I would recommend Steelie Gears, I've used him before and he does good work.
     
  4. HSV08

    HSV08 Member

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    The m80 is in the s/c 6 diff. The senator is a series 1 so m78. Will the LSD from the 80 go into the 78 shell? And I'll need to find some gears from a manual ls for the 3.46 right? Unless I keep my diff thats under there and buy your set off you? Been to steelie before. Doesn't seem bad!


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  5. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    BW 78 and 80 aren't interchangeable (but it is possible to fit the entire 80 diff assembly into the earlier model cars). In reality I don't think that there is anything wrong with the 78, they are plenty strong and there are a couple that have lived under the rear of 9 second cars.

    The advantage of the BW80 diff is that the Eaton truetrac centres can be bought from the US a LOT cheaper than you will get one for the 78 but if your happy to go with a properly tightened factory LSD then that isn't a problem.
     
  6. VN_SS_CM

    VN_SS_CM Member

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    quick question would it be possible to put a 3.27 falcon 7.8 crown and pinion into a VN V8 borgwarner lsd 28 spline....ive heard the pinion on the 7.8 is shorter then the 7.5 pinion by about 2mm if so could you space out the bearing from the gear to cater for the 2mm?
     
  7. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    Should be fine. The early BW diff used in the VK were the BW75 and the gear sets/centres are interchangeable with the later BW78 diffs found in the VL-VS models.

    I do believe that some early HSV models did come out with 3.23 gear sets.

    Having said that, going from a 3.08 to a 3.27 ratio will make about 100rpm difference.
     
  8. 13timbob31

    13timbob31 New Member

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    I have a 98' v.s holden v.6 ute it has a lsd but doesn't behave like on when its off stands, after reading ur post I tried to find a harrop/eaton 28 spline "early" true trac center but I want to use PayPal to purchase one but I couldn't see that option for there websites so I started looking around and found only 31 spline "early"true trac if any one has one to sell or know of were I can go to get one the way I need too please advise, also my brother seems to think that dropping the oil out, flushing it with diesel, emptying it then putting new oi in might bring it back to life any thoughts?

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  9. Fiorentesteem

    Fiorentesteem New Member

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    So my VS static diff (trailing) can't be removed and exchanged for the VS Calias IRS I have sitting in carport?
     
  10. Fiorentesteem

    Fiorentesteem New Member

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    Maybe a custom replacement could be Jag diff?
     
  11. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    I wouldn't think so, the LSD single pegs when their isn't enough friction between the cones and the LSD housing due to wear. When the cones/housing wears, the cones effectively bottom out in the housing. The only way to fix that is to machine the end face to get the proper clearance. A simple oil change won't fix the mechanical wear.

    You can't fit an IRS setup into a chassis manufactured with the live axle diff as the mounting points are different.

    Not sure why you would even want to do this. IF you want IRS, the best option is to buy a vehicle with it fitted from the factory.
     
  12. _R_J_K_

    _R_J_K_ Well-Known Member

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    Waste of time and money. If you want IRS that badly, it would be cheaper to get a Commodore that already has it. The Commodore IRS setup isn't really that great either.

    Also, if I were to use a custom diff setup I would get an R200 from a Nissan or a BW80 from a late model Commodore. Both of these have heaps of aftermarket support.
     
  13. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    I wouldn't say the Commodore IRS is that bad. The VR/VS models can use some strengthening of the rear subframe. The biggest problem is that the design was borrowed from another model, however Holden decided they didn't need the toe arm link that was part of the original design. HSV decided that the toe arm link was required and fitted them on the HSV (VT GTS) models, Holden saw the light eventually and fitted the toe link arm as standard equipment from the VX 2 onwards.

    I've got both versions (IRS and live axle) of the VS Commodore and the IRS does ride better.

    One of the suspension outfits actually worked at designing a kit to retrofit the extra toe link arms to earlier models, unfortunately they decided that it was simply easier to just retrofit a VX 2 rear suspension into the earlier model cars but this doesn't work for those of us who have VR/VS model Commodores.
     
    Last edited: Feb 24, 2014
  14. _R_J_K_

    _R_J_K_ Well-Known Member

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    I mean comparatively to the rest of the automotive world. Most manufacturers stopped using a better version of the swing arm setup in the 80's. For me, toe adjustment doesn't really make up for its lack of adjustability else where.
     
  15. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    What other adjust-ability do you need in the rear suspension? Between the toe link adjustment and fitting a 2 way adjustable bush for camber (or the 4 way adjustable bushes for the earlier models) there isn't much more required for the rear end.
     
  16. _R_J_K_

    _R_J_K_ Well-Known Member

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    The ability to set everything with a turnbuckle or replacement arms. The bushes may be adjustable, but they are hardly easy to set. I'm not really a fan of the separated spring and shock either, it really limits your options in the back. It's a shame that the VE setup didn't come out 10 years earlier.
     
  17. immortality

    immortality Home of the smoky breakfast Bacon! Staff Member

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    TBH I'm not a fan of the spring/shock arrangement either (both IRS and live axle) but I guess we can't have everything ( A simple strengthening of the chassis shock mount would have allowed for a proper coil-over type set up in both configurations).
     
  18. DCEIVDU

    DCEIVDU New Member

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    I think leave it here. Great write up. Has cleared A lot of unknown territory for me so thanks a bunch
     
  19. jsnolea12

    jsnolea12 New Member

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    a friend of mine has a vr v6 commodore ute, will a diff centre out of a sedan bolt straight in? as having trouble finding a ute diff for it
     
  20. gluten3

    gluten3 Member

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    It came from Opel Omega. Opel copied simple IRS from BMW 2002 (early 70s). It did not have toe control link. Holden used this from VP-VT. Opel added the toe control link at the end of 1993. Holden did not until VX II, but still made VZ utes without toe links, so they are well and truly lagging behind.
     
    Last edited: Apr 19, 2015

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