Locking differential - why not?

Thread in 'Technical Questions' started by Tree, Nov 26, 2015.

  1. Tree

    Tree New Member

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    Hey peeps,

    I've got a Volvo 740 and finding performance parts for the car is not easy. I knew the consequences for choosing such a car but I wanted to be different to the usual Nissans and jap imports. Currently I've got it welded but I have to get a roadworthy check done and my mechanic won't pass it (legalities). I have a few options. Unfortunately no clutch LSDs off the shelf.


    1. Head to the wreckers and swap in the open diff, change back to welded later
    2. Buy a true-trac helical LSD - Legal but no good for drifto
    3. Aussie locker, detroit locker aka automatic locking diff - pretty cheap $3-400. Easily installed. Might not be legal but a possible option nonetheless.
    4. Jeep XJ Cherokee rear diff (Dana 35) clutch LSD. Suggested by another Volvo-er. Unsure of fitment as the Volvo is Dana 30 (XJ Jeep FRONT).

    I've trawled the internet and no one seems to use locking diffs, but maybe because all popular makes have off the shelf stuff like KAAZ or come stock with VLSD. My understanding is that auto lockers allow a bit of slip when turning but locks up when torque is applied. They work like a ratchet so wheels cannot slip backwards. All mechanical clutch LSDs lock under acceleration so I don't see much different here.

    Perhaps someone with experience in the locker can chime in?
     
  2. Tree

    Tree New Member

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    No takers?
     
  3. Kingk

    Kingk Member

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    Keep the welder in and sling an open diff in once a year for the test
     
  4. JasonER34

    JasonER34 Member

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    Do the same as most to with de-cat emissions pipes, fit the legal parts for the test, then as you please until the next test.
     
  5. miffy

    miffy Member

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    A locked / welded diff isn't a fail in uk

    - - - Updated - - -

    Assuming your uk
     
  6. Kingk

    Kingk Member

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    I think he's in Australia
     
  7. miffy

    miffy Member

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    If that's the case , your only chance is getting a legitimate diff and declaring it propa , ausi laws are clear and unavoidable
     
  8. stevieturbo

    stevieturbo Member

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    It's 100% a fail here in Northern Ireland and pretty sure totally illegal everywhere in the UK regardless of what might happen at MOT.

    Is it an actual locking diff you want, or just a good quality LSD ?

    eg would this fit ? They can offer different ramps for different amounts of lock

    Volvo RWD Gripper Diff (Type 1030 / 1031) Volvo RWD Gripper Differential. We ship worldwide [] - £967.68 : Gripper Differentials, 5% Off. Free Post. In stock. Gripper Diffs/LSD

    Or some of the old Volvo turbos had LSD's from the factory.

    diff_lsd_volvo_dana

    Volvo Rear Ends
     
    #8 stevieturbo, Nov 27, 2015
    Last edited: Nov 27, 2015
  9. Kingk

    Kingk Member

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    Doesn't Northern Ireland have the same not test as the rest of the UK? And welded diffs do pass a UK mot
     
  10. stevieturbo

    stevieturbo Member

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    Mostly it's the same, ours is a bit stricter in some areas.....perhaps a lot.

    Pretty much the first thing after basic lights/emissions checks you drop into the rollers for the brake test. As soon as the rear wheels drop into the rollers the locked rear would be detected and it would be an immediate fail.

    Interestingly, looking through the manual it doesnt specify anything relating to it

    It's definitely illegal on a road car though....cops have even been known to pull people for it at roadside checks aimed at harassing modified car owners.
     
  11. Kingk

    Kingk Member

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    Here you need to inform the tester its welded, then they'll need to take the car on a road test to make sure it's safe to drive on public roads
     
  12. Stavros

    Stavros Active Member

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    In the UK some people will fail it, but they've got no right to.

    Same as some cops will kick off, but their 'rules' are made up as they go along- Fairly certain there's fuck all set in stone about them.

    If locked rear ends was illegal most quad bikes couldn't be made road legal as they're just a solid bar for aside from a few big ones...
     
  13. stevieturbo

    stevieturbo Member

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    A quad bike is not a passenger car though just the same as there will be different rules for different vehicles.


    And with a locked rear, it is impossible to carry out a proper and full brake test.

    A road test will never be able to determine individual wheel braking ability as the full test does and requires to determine any imbalance from side-side and indeed front-rear.

    I dont even think you have an option of a road test here and I'd agree it's for very good reason.

    As for cop rules, whilst most are dumbasses, I'm sure you will find the rules are set in stone under Construction and Use terms, if of course there's anyone who can actually understand them.
    Problem is when a dumb cop makes an allegation, he then has free legal might behind them to pursue it...whereas you need to pay for your defence. It's a losing battle all the way whether innocent or not.
     
  14. olliethrwollie

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    It is not an mot failure any car with lsd or 4 wheel drive that may damage the car during an roller brake test(rbt) must be taken out on the road for a tapley meter/decelerometer test.as you cannot tell it's welded from visually looking at it worst you could do is pass and advise
     
  15. stevieturbo

    stevieturbo Member

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    4wd or cars with an LSD are tested on different rollers here. If placed on the wrong rollers and any resistance is met the test is immediately stopped and if need be vehicle moved onto the correct rollers.
    But there is no possibility of damage.

    Not 100% sure on what the difference is, but there is no option for a road test and there is no need for a road test here. And it is better this way as you know all the brakes are tested properly.
     
  16. Tree

    Tree New Member

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    HOLY F%^&* someone actually makes clutch LSDs for the brick. But costs an arm and left testicle. But still, they make one *sniff* (happy tears). I've read both but missed the part where the Dana Power Lock was a clutch plate doh! Wouldn't be easy to find tho and sourcing the rebuild parts? But could still end up cheaper than the gripper.

    I wanted to know if anyone drifts with an auto locking diff like an aussie locker or detroit locker commonly used in the 4WDing or drag racing. I've done my homework and I realise now this is NOT what we want. This is because auto lockers/locking diffs only lock in a straight line and slippery surfaces but will allow wheel differentiation during corning like an open diff. Case solved shut :D

    We used to be able to get "lenient" road worthies but the cops and auto-governing bodies are cracking down on it, very serious consequences if you are caught giving out dodgies.

    KingK - How did you know I was from Australia? (before I updated my profile just then)
     
  17. stevieturbo

    stevieturbo Member

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    Whilst not a locker, and still not cheap ( none will be cheap ), The Wavetracs are supposed to work better than a regular Torsen

    Dana 30

    Wavetrac Differentials - Volvo 1800/14/240 DANA 30 Rear, Wavetrac, 48.309.131WK, Volvo, Differential

    I just fitted a Wavetrac to my own car a few weeks ago, but unfortunately with weather etc it'll probably be next year before it gets any abuse. I dont do drifting though. I had a regular Torsen before it, but on tighter corners etc it would allow one wheel to spin a fair bit. The Wavetrac should help resolve this behaviour.

    The Gripper plated type diff would definitely be better suited to drifting though

    Maybe some of the turbobricks guys have options ?

    http://forums.turbobricks.com/
     
  18. Tree

    Tree New Member

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    Yeah I've gone thru quite a few threads, digging up some useful info even tho it takes a while to catch a quality post. I've been able to organise a roady thru a mate so I can leave the diff welded for now whilst I continue to build the list of limited options. Thanks for the input folks and esp linking me the gripper stevie! I don't mind that sort of price once I decide to get serious.
     

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