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Limited slip in a 9 inch?

Discussion in 'The Hokey Ass Message Board' started by PeteMattersen, Oct 15, 2012.

  1. I have a 9 inch ford in my model a and am looking at Limited slip set ups. Any testimonials for what you guys are running would be great. I have been looking at the powertrax no slip unit. It is pricey but I like the fact that I don't have to change my ring and pinion set up.Just got the car back on the road and want to haul some ass.Please no "get a quick change" or "run a banjo" comments. Thanks in advance.Here's a pic of her in final stages.
     

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  2. big duece
    Joined: Jul 28, 2008
    Posts: 6,830

    big duece
    Member
    from kansas

    The good ole trac-loc is pretty reliable. New ones are around 400, used are 100-150 clutch packs are 50bucks or so.
     
  3. big vic
    Joined: Jan 3, 2010
    Posts: 400

    big vic
    Member
    from cary il

    yeah trac-loc is a tried and true setup that can be found easily
     
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  4. ididntdoit1960
    Joined: Dec 13, 2011
    Posts: 1,030

    ididntdoit1960
    Member
    from Western MA

    The powertrax or lokrite are poor mans detroit lockers primarilly targeted at offroaders - you will hear/feel them lockin and unlocking - likewise, if you use one of these on the street make sure you are pointed where you want to go before you "punch it" as these will launch you straight with no "clutches" like a traditional posi to slip......the ford posi is called traction lock and that would be my choice for a light, moderately powered street driven car
     

  5. Cornering is fairly important to me. I like that Elpolacko,thanks for the link.
     
  6. All American 6
    Joined: Sep 25, 2012
    Posts: 234

    All American 6
    Member
    from Sumter, SC

    A $30 mini spool is as cheap as it gets. I ran one for years on a blown small block with 28 spline axles, 275/50-15 TAs. (I drove it like I owned it)
     
  7. I'm afraid that would give me crazy understeer. Thanks but cornering is as important as straight away to me.
     
  8. What's wrong with an O.E.M. unit?
     
  9. JEM
    Joined: Feb 6, 2007
    Posts: 1,040

    JEM
    Member

    There's several flavors of limited-slip if we leave out the manual-locking 4WD diffs:

    Preloaded friction limited-slip (GM Positraction, Ford Traction-Lok, etc.)
    Ratcheting locker (Detroit Locker)
    Hydraulically-actuated friction limited slip (Hydratrak, Viscolok)
    Viscous limited-slip
    Helical-gear torque-biasing (Torsen, Truetrac, Wavetrac, Quaife, DPI diffs)

    The preloaded friction limited-slip is the most common type. They work well enough though they wear.

    The hydraulically-operated friction diff uses friction elements but instead of springs or wedges to actuate the locking it has a hydraulic pump driven off a side gear, more slip means more pressure. Seen in some late-model cars as OE but not common as aftermarket.

    The ratcheting lockers are nasty in street use and not a lot of fun in most track applications but they're tough, you see them in some oval and road-race series where they are for some stupid reason required by rules.

    Viscous limited-slips have more or less come and gone, AMC used them in the center diff of various products in the '80s, Nissan, Alfa Romeo and Euro Ford used them in car axle diffs in the '90s,

    Helical torque-biasing diffs are the only type that don't attempt to make the heels turn at the same speed, instead they move torque to the wheel that resists more. Downside to some models without preloading (Quaife, Truetrac, non-R Torsen) is that if one wheel lifts they go open - so the offroaders don't like 'em and some high-CG road-course cars may have trouble too. Mostly they work great. Some designs have preloading elements to keep enough friction in the gears to keep them from going open.
     
  10. rpivinton
    Joined: Jan 24, 2009
    Posts: 34

    rpivinton
    Member

    I can tell you from experience that you will learn to hate a Powertrax type ratcheting locker on the street. You must learn to coast around corners to let it unlatch and then relatch before you gas it up or you will be in the other lane when it latches. On the highway, it will freak you out the first few times it unlatches and relatches when going around a gentle curve. Makes the rear of your vehicle shift sideways momentarily (bad news on slick roads). Backing one up and turning at the same time out of a parking place will make you swear things are breaking inside the rear.
    These things are a fabulous piece of engineering and work great for their purpose (off road), but the street ain't it. Get a factory trac-loc and be happy. Easy to install, you only have to pull out your open differential and swap the ring gear onto the trac-loc, new carrier bearings, dial in the backlash with the spanner nuts, and you're done.
    Bud
     
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  11. JEM
    Joined: Feb 6, 2007
    Posts: 1,040

    JEM
    Member

    I'll throw in one other comment, more related to road-course use than anything else.

    A diff that tries to equalize wheel speed will tend toward 'push', or understeer. The more aggressively it tries to equalize wheel speed, the more push you get. The extreme example, of course, is a spool.

    The friction diffs act more moderately, once again the more aggressive they are the more understeer-biased the car will be.

    A ratcheting locker typically goes from locked (push) to open (whoops!) if you back off. Big swing in attitude if you don't stay in the throttle.

    The torque-biasing diffs do not try to equalize wheel speed, and will therefore feel 'looser' if you do not otherwise adjust the car setup. Some people really like the feel, some don't.

    The factory 4-pinion Trac-Loks are good, the Truetrac is good too and very attractively priced for what it is - but as with so many such things the box arrives and it says 'Made in Taiwan'.

    The Wavetrac is a very, very interesting looking piece of hardware, I haven't yet had my hands on one, it's twice as much as a Truetrac but somewhat less than a Quaife for the same application, and it's got adjustable preload springs to deal with the lifted=open situation.

    If you want a few laughs, not really a product for HAMB-compatible cars but go google 'OBX differential'. Chinese worm-gear diff, apparently the gears and case aren't bad if you get one that's machined correctly but they're assembled with random garbage hardware...
     
    Last edited: Oct 15, 2012
  12. good info. Jem thanks for the advice. Uninterested in stuff made from chinesium! HA
     
  13. Don's Hot Rods
    Joined: Oct 7, 2005
    Posts: 8,319

    Don's Hot Rods
    Member
    from florida

    I've never cared for a lot of limited slips in a light, high hp car, but I have a Trac loc in my 27 and it is just like having a one wheeler until you plant your right foot. Even if I goose it going around turns it still doesn't want to steer the car at all.

    Don
     
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  14. gc427
    Joined: Aug 10, 2009
    Posts: 122

    gc427
    Member
    from SoCal

    Trac-lok is the way to go if you want to drive it hard and enjoy going around corners.

    Most of the locker style units will make you wish you had a trac-lok unit.
     
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  15. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    I have a Detroit TrueTrac in every 4 wheeled vehicle I own (except the lawnmower), and in BOTH ends of my 4x4 stuff. It is a torque-biasing limited slip. Seamless, nothing to wear out, no additives.

    Everybody I have known to install a Powertrax locker, or other similar units that go inside of an OEM carrier has catastrophically broken it, leaving the vehicle immobile.
     
  16. JEM
    Joined: Feb 6, 2007
    Posts: 1,040

    JEM
    Member

    The rock-crawler guys don't like Truetracs because when one wheel comes off it spins and it acts like an open diff; to some extent you can supposedly get around this by riding the brakes to keep the wheel loaded against the brakes. Never been in that situation so I can't say how it works.

    The only other issue with the quality helical diffs is that if you work them hard (that is, 20+ minutes of hard road-course use in a reasonably high-HP car) they make heat and you'll probably need a pump and a cooler.
     
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Have them in my trail rig too. It has individually controllable brakes, for each wheel.

    Neither example you have posted, while both true, is pertinent to the OP, though. He'll be fine.
     
  18. Dane
    Joined: May 6, 2010
    Posts: 1,351

    Dane
    Member
    from Soquel, CA

    I'm hearing only good things about those...
     
  19. Really only interested in street applications. Not doing a lot of rock crawling with the old girl.
     
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  20. Jay Tyrrell
    Joined: Dec 9, 2007
    Posts: 1,631

    Jay Tyrrell
    Member

    This is what I am running! ^^^^^^^^^^^^^^^^^^^^^^^^

    Fluid wise make sure that you run a good quality fluid. I run a 75 140W Valvoline Synthetic Limited Slip. Great diff fluid! Nice and quiet for the 4:56 rear end that I run.
    J
     
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  21. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    Just the thing for those lacking enough excitement in life.:eek::p I have a locker in my falcon. Car handled so bad anyway, it really didnt make much difference. Cornering at anything even close to the limit would cause your life to flash before your eyes..:eek:
     
  22. Ha, I run one in my 1840 lb t-bucket, when making a turn onto another road from a stop it will chirp second gear in about 5 ft. It is fun and pulling out quickly under throttle is an experience ...lol
     
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  23. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,910

    dirty old man
    Member Emeritus

    My SBC powered "A" roadster has a Powertrax in the 3.70:1 9" rear. Spent a few hours about 3 Sats ago on it's first test drives. Now back in the shop for changes/etc. unrelated to differential.
    All the test driving was done on city streets and suburban roads. Never felt or heard any strange stuff from the rear including backing under power while turning.
     
  24. 61falcon
    Joined: Jan 1, 2009
    Posts: 772

    61falcon
    Member

    put a real detroit locker in it. i dealth with clutch type diffs in my Falcon and after burning up 2 clutch packs over a few summers of street and track fun i put a detroit locker in it and after doing so i realized thats what i should have done from the begining.
     
  25. APACHE FS
    Joined: Feb 20, 2007
    Posts: 569

    APACHE FS
    Member

    Detroit locker will hand you another if there's any problem too, I run it in my Daily OT 4x4. Not too noisy or unruly. But not open for sure


    Posted from the TJJ App for iPhone & iPad
     
  26. k9racer
    Joined: Jan 20, 2003
    Posts: 3,091

    k9racer
    Member

    I have a unit made by a company called Gleason. It has something like worm gears in place of the spiders. One is in my OT Road race car 85 mustang steda. I also use these in my asphalt circle track cars. These units got rid of my center of the corner understear {push}. I have just picked up another unit that will go in my 55 ford.
     
  27. Engine man
    Joined: Jan 30, 2011
    Posts: 3,480

    Engine man
    Member
    from Wisconsin

    Hens teeth!
     
  28. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    The Gleason, Torsen, and the TureTrac are all of the same variety of torque biasing limited slip. They are all gear driven, and work the same way.
     
  29. SOHC427
    Joined: Apr 5, 2009
    Posts: 1,048

    SOHC427
    Member

    Stick with a trac loc. 28 or 31 spline, easy to find, and pretty tuff, in a light car.
    Early Bronco's have 28's and f100/150's with 31's. 73-86
     

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