Going from OE Traction-lock to a 2.7 bias Torsen. Finally.

Discussion in 'Drivetrain, Exhaust and Electrical' started by Norm Peterson, Jun 18, 2019.

  1. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    And it's the potential change in the handling balance that I'm still wondering about. I've never driven a Torsen-equipped car before, so I don't really know if it's going to make the car a little looser or a little tighter or how it's going to respond to lifting off of the brakes. I'd rather have a little heads-up for needing something like either more or less rear bar, than give myself too big of a surprise.

    There's a mild gear change happening as well, 3.55's to 3.73's. That's it for now, but there's more to come.


    Norm
     
  2. steveespo

    steveespo Lord knows I'm a Voodoo Child Moderator

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    Best thing you can do for a road raced Mustang-add the Torsen.
    No ill effects to handling.
     
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  3. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    Just do it! It's not gonna affect balance at all...just the ability to put the power down. At least that's the way it felt to me when both cars were on similar (Boss) suspensions and the Torsen was the main difference.
     
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  4. domesticpower

    domesticpower Track Addict

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    My car didn't have the Recaro package so I had the OE trak lok diff and I tracked the car with it a couple of times before I bought an OEM replacement Torsen. Night and day difference. You can get back on the power much, much earlier. It was almost like going from a good summer tire to R comps in the back. I didn't notice any extra push. Theoretically, there should be a bit more because you'll put more power down, more weight transfer to the rear and less grip in the front... but being able to get back on the power that much earlier does help with making small adjustments to correct the line with the power. Unless you are jumping curbs, I don't see lifting a wheel and running into the limitations of the Torsen. I think you'll love it.
     
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  5. TymeSlayer

    TymeSlayer Tramps like us, Baby we were born to run...

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    ^^^ Ditto ^^^

    My car also did not come with the Torsen and throwing it on made a huge difference. Made me wonder WTHIWT when I ordered the car without it.
     
  6. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    Kind of what I was fishing for. I'm also curious about the left-right distribution of torque as it affects yaw. Getting more torque to the outside wheel under power ought to be a mildly "loosening" effect if that's what happens. I'm not sure how the 'R' part might affect that, or off-throttle turn-in (it's the M-4204-MB).


    Norm
     
  7. Eric62

    Eric62 TMO Intermediate

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    Did quite a few track days with the traction-loc before switching to the T2 Torsen. Balance is just about the same but he car turns-in far better and puts power down better. You no longer have to break the clutch pack loose just to get the car to turn, it just rotates smoothly when you trail-off the brakes and roll back on the throttle. If you did any "tricks" to make the car turn like crank the rebound damping on the rear shocks up high and/or reduce the front compression damping you can back that off a bit.

    I think you'll see a bigger change going to the 3.73's. You'll need to dial up a bit more XXoversteerXX UNDERsteer (sheese, stupid mistake!) to allow you to use all that extra torque now going to the rear wheels.
     
    Last edited: Jun 23, 2019
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  8. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    Thanks Eric.

    Make that 3.73's and a more realistic ability to use 2nd gear (taller than the 2.00 that the car presently has, shorter than the 1.32 3rd) out of the slowest corners.


    While I'm at all this I may raise the rear ride height a little to make the rear axle roll steer effect a little less understeerish (it's down almost 3/4" even after being shimmed up from -1.1" or so). That should give me a little more headroom on rear shock setting for corner entry anyway. I don't see the anti-squat changing enough to matter (stockish 4.6L 3-valve), but I might look into using the longer UCAs from the later year S197s to slow the variation in A-S down a bit.


    Norm
     
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  9. domesticpower

    domesticpower Track Addict

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    It sort of is. Torsen locks up under power because the axial thrust forces bind the gears with the diff case as you may know. The more you feed the power, the more it will lock but as long as you aren't overpowering the inside wheel, you are just (mildly) locking the diff and making no difference in handling (a slight bit of push from the back due to locking). Once you give it enough that the inside wheel is starting to spin, torque will get biased to the outside and you will get some useful rotation from the back without even forcing the back end to come out to point the nose.

    By 'R' do you mean you got the T2R racing version? If so, it has a higher torque bias ratio so more aggressive locking under power, but same principle applies. You'll have to start overpowering inside to get any useful rotation. Until then, it'll push. Some T2R racing versions have preload/clutches so they operate like lockers when you left a wheel. All Ford's OEM Torsens have no preload so if you lift a wheel completely (zero traction on the inside), it behaves like an open diff.
     
  10. Norm Peterson

    Norm Peterson Corner Barstool Sitter

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    I got the -MB version, which I understand is what the Boss 302 Laguna Seca got as OE. It's the 2.7 bias version, not the FR500 competition-level 4.0 unit.

    A non-locking Torsen is probably better for my purposes and power level, it's just that I was getting different indications (R vs non-R) while I was shopping for it. Compared to the 5.0 cars, a 4.6L GT is a momentum car.


    Norm
     
    Last edited: Jun 23, 2019
  11. domesticpower

    domesticpower Track Addict

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    Oh ok, that's good. I agree, I think a non-locking and lower bias Torsen is probably better. I'm fairly sure that 2.7 is OEM only. If I remember correctly while I was shopping, the T2R came in 4:1 and 2 or 2.5:1 but never 2.7. Good luck, hope you enjoy it!
     
  12. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    The OEM Boss 2.7:1 bias unit *is* a T-2R.

    Just to add to the confusion. ;)
     
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  13. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    https://trackmustangsonline.com/threads/changing-rear-ratio-for-track.14306/page-2#post-211472

    "(T-2R) differentials are in the 2nd generation of design, now employing Equvex II parallel-axis gears, which make use of Split-Gear technology. Split-Gear, first introduced for the 2012 Ford Mustang Boss 302, uses a helical spline coupling to the side gears. This gives the model tunable friction characteristics, allowing it to meet OEM customers’ specific needs in a way no one else in the industry can."

    https://torsen.com/how-it-works/

    [​IMG]

    This helical spline 'update' is a good reason IMO to go with the Boss unit. Probably also the main reason it costs more.
     
  14. domesticpower

    domesticpower Track Addict

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    Haha thanks Grant... I remember being confused by that too at the time. 'R' was reserved for Race version at the time, then when they released the 'R' Revised version with the Boss 302, it became R. There was no confusion for a while if I remember correctly because the Boss 302 version was exclusive to Ford for a couple of years. I contacted Torsen at the time to buy one hoping for a better price and they said you could only buy it through Ford or its distributors. Ford owned the tooling for the diff and Torsen was only authorized to sell it as replacement for OEM equipped cars. Cool that Ford must have had a hand in developing it.
     
  15. Grant 302

    Grant 302 OPM Spent: $665,833 Moderator

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    Yeah, T2-R2 would imply it was from a long time ago...

    ;)
     
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  16. domesticpower

    domesticpower Track Addict

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    Haha yea, no doubt.
     
  17. ChrisM

    ChrisM No bad days.

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    This thread is relevant to my interests.
     
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