OS Giken vs Torsen

Discussion in 'Road Racing Forum' started by RedRocks, Jun 11, 2018.

  1. RedRocks

    RedRocks TMO Intermediate

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    I’m at the point in my build where I wanna upgrade the rear differential. Here’s some details on my current setup:

    2008 Mustang GT
    2.3 Whipple/Car Dyno’s @ 510 rwhp
    MCS Coils
    Whiteline Watts
    Forgestar 18x11’s
    315/30/18 BFG Rival S in all fours

    Given that I’m running a decent amount of horsepower and tire I want something that can put the power down better and hopefully be more reliable than the stock LSD. I autocross and track this car on a regular basis.

    Now after some research I know the Torsen has no clutches to wear out but seems to be slightly slower than the OS Giken. I’m leaning towards the OSG for this reason. Most of the tests I have seen though have been on Miatas and S2Ks which are a lot lighter and have less power than my S197. Have any of you driven or owned an OSG equipped Mustang? Is it smarter to stay away from “hybrid” clutch operated LSD’s such as the OSG?
     
    Last edited: Jun 11, 2018
  2. Gab

    Gab Bullitthead

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    While I can’t comment or answer your question, I’m curious how the 315’s work on a 10” wide wheel. Have you ever had any issues with that combination? I apologize in advance for hijacking the thread. :D
     
  3. Mad Hatter

    Mad Hatter Gotta go Faster

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    That's kind of the first thing that sprung to mind!! Section width 12.6" :confused:
     
  4. RedRocks

    RedRocks TMO Intermediate

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    Oops I meant 18x11 I typed it wrong. I have the Vorshlag setup
     
  5. racer47

    racer47 All I got left is fast

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    Get an Eaton Truetrac. They are reasonably priced and damn near bulletproof.

    http://www.eaton.com/Eaton/ProductsServices/Vehicle/Differentials/detroit-truetrac/index.htm

    I've beat the crap out of a couple of these on various cars with no issues. Currently I've got a 2.8 KB with a bit more power and have run drag radials, A7s and R1S's with the Trutrac and it works great.

    As far as 315's on 10's, I run them too. Its not ideal. There is some flex but its still faster than 295s and a lot faster than 275s which some say is the most you can run on a 10" wheel. I've given up debating about this because some Dudley Do Right will always argue to death that its not right. But my results beg to differ.
     
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  6. ArizonaBOSS

    ArizonaBOSS Because racecar. Moderator

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    Not sure I know of anyone that is really pushing these cars to their limit that runs the OSG. I would love to hear some feedback on it from someone who is already very fast. That being said, I am quite happy with my T2R.
     
  7. racer47

    racer47 All I got left is fast

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  8. ArizonaBOSS

    ArizonaBOSS Because racecar. Moderator

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    Good lord. Maybe that's why we don't hear of anyone using them. That is nuts.
     
  9. RedRocks

    RedRocks TMO Intermediate

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    The OSG is run on many CAM cars in autocross and seems to be the diff to have if you have the money for it. That being said I don’t know any road racers with one on a Mustang. Haven’t explored the Eaton at all.
     
  10. RedRocks

    RedRocks TMO Intermediate

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  11. racer47

    racer47 All I got left is fast

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    Thats nuts. There is no way that diff is $1500 faster than a Trutrac. The trutrac is completely unloaded left to right with no power, it never spins an inside tire coming out of a tight corner, it just works like you think a diff should.

    The torsens, t2r, supposedly have a higher bias ratio, which is directionally better, but as long as it freewheels unloaded and doesn't spin 1 tire loaded, than you have enough bias. There were some reports on s197forum of drag race guys and higher hp cars braking the t2rs. Not many, but there were some. Its not meant as a drag race diff anyway. But since you're making more hp, you may want to factor that in. But for autox, I doubt you'd have an issue.
     
  12. RedRocks

    RedRocks TMO Intermediate

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    I read that about launches on the T2R as well. The only time I think that would be a factor for me would be the drag style launches in Pro-Solo. The T2R seems to be the choice for most road race applications with True Trac almost same. Only issues I’ve read on True Trac have to do with IRS cars lifting wheels or tight autocross courses which may be a problem for me.
     
  13. racer47

    racer47 All I got left is fast

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    Yeah, i've heard that too but never experienced it. I've run tight autox's and never spun an inside rear wheel. I also run 85w140 non syn gear oil which makes the diff slightly tighter. Its hard to say exactly how much though.

    I never had an IRS so I can't comment there.

    There is also the DPI Platinum Trac diff. Its a torsen style diff with preload that makes it not freewheel under no load. If you have 1 rear tire off the ground a torsen will not apply power to the tire on the ground. The preloaded torsens will apply torque to the tire on the ground. I looked into them years ago but never bought one. The more preload, the tighter the diff. They call it 1/4 tight or 1/2 tight. Either way, it makes it the bias higher and doesn't allow inside tire spin. They are about $1000.

    Everyone calls it DPI (Dan Press I think) but the company was sold to Larson.

    http://www.larsenracingproducts.com/products/8-8-31-spline-platinum-track.html
    https://www.svtperformance.com/forums/threads/torque-sensing.736421/

    But honestly, even if I had $1000 burning a hole in my pocket and I needed a diff. I'd still buy the $400 Eaton plus a new tire or two.
     
    Last edited: Jun 12, 2018
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  14. DocB

    DocB TMO Intermediate

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    Although I have a Torsen T2R in the race car and the Cobra, and am quite happy with both, you might want to check out the WaveTrac diff.
    For the money, can't be beat. Bias and strength.
     
  15. RedRocks

    RedRocks TMO Intermediate

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    Another one I haven’t heard of till you mentioned it. Stumbled onto a BMW forum where there was good discussion about the Quaife, OSG and Wavetrac. Seems the Wavetrac is the only diff that can lock up and power the gripping wheel with one wheel completely off the ground. I did find some guys in the SVTPerformance forum that advised against them because of failures and C-Clips getting jammed. The OSG fanboys in the BMW forum love the adjustability of that diff as you can order it as a 1,1.5 or 2 way diff with different preloads based on setup. The Quaife seems to be like the TrueTrac, a bulletproof dependable upgrade from stock. Tough to really make a judgement without experience. Seems the overwhelming majority of roadracers on here run the T2R.
     
  16. Speedboosted

    Speedboosted TMO Intermediate

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    I run a Boss Torsen in my car and put a True Trac in my Dad's GT500. While they're two completely different cars, I think both are excellent and have taken abuse. To me, the value that the True Trac brings to the table simply cannot be beaten unless you are competing for mere tenths or even hundredths at Nationals.
     
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  17. Grant 302

    Grant 302 OPM Spent: $328,347 Moderator

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    I don't get the point you're making here.

    If you're class limited to a tire size, I'd still recommend running a wider rim if allowed. If you're unlimited with tire size, perhaps when you run the 315, I don't see why you'd choose to run them on a 10" rim. Managing wear and using the whole tire is difficult (IMO) with a severely pinched on tire. I can't even think of a 315 where the manufacturer lists a 10" mounting option...


    People are overly concerned about this IMO. If any of the Torsen varieties were easily broken you'd hear about it here.

    My concern over the OSG would be if you'd really change the cones and springs, etc. to 'tune' it for your use(s). That seems to be the main advantage for getting one. And would it really be worth the 100ths once you get it 'tuned'?
    [​IMG]

    s-l1600-401.jpg s-l1600-400.jpg s-l1600-399.jpg


    Also note that there is some confusion about the T-2/Boss/T-2R Torsens. The Boss is also a T-2R design, just with the 2.7 bias . The FR-500 or 4.0 bias unit is also a T-2R, but often the only one referred to as a T-2R.

    T-1:
    [​IMG]

    T-2:
    [​IMG]

    T-2R:
    T2R_webplS.jpg

    Spotting an assembled "R" should be easy and see the Thrust Plate differences:
    https://torsen.com/product/ford-8-8-t2r/
    [​IMG]
    or
    https://torsen.com/product/ford-8-8-31-tooth-spline-t2r/#
    [​IMG]

    T-2:
    https://torsen.com/product/ford-88-31-tooth-t2/#
    [​IMG]

    JMO, but I'd get the 4.0 bias T-2R for AutoX or tight courses. Boss T-2R for track.
     
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  18. Grant 302

    Grant 302 OPM Spent: $328,347 Moderator

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    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.
     
  19. racer47

    racer47 All I got left is fast

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    Gab asked about 315's on 10" wheels. So I replied. I'm not class limited. I make the fastest car I can make with a given amount of money. Sure 11" would be slightly faster. But 11" wheels are a lot more expensive than 10" Drifts. As I said 315s on 10s is not ideal but it is fast. I'm not sure who reads this board on their phone vs desktop or who has sigs off, but if you see sig pics, my imsa gto car is not goodyear lettered for no reason.

    As far as braking diffs, road racing is not particularly hard on diffs especially at stock power levels. So you may not hear about failures on this forum. The svt and s197forum guys break diffs due to high hp and/or drag racing. RedRocks 510whp is up in the range where others have broken t2r's.
     
  20. Grant 302

    Grant 302 OPM Spent: $328,347 Moderator

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    And that was just a question stemmed from a typo.
    I see it more like if you can afford and fit 315s, then you can afford and fit 18x11s... When I only was using the drifts, I was happy running between 275s and 305s. I didn't and still don't get the open recommendation to run the 315s on 10".

    Generally agree, but HP doesn't kill diffs. It's just the 'jerk'/shock of launching with a relatively high final drive torque and slicks+ track prep to resist it. Short of that, people shouldn't be breaking any diffs on the road course even with 800 HP. JMO, but keeping the fluid cool on track is a bigger factor in diff longevity for road racing.
     
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