240z diff replacement or refurbishment? | The Z Club of Great Britain
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240z diff replacement or refurbishment?

Discussion in 'Drivetrain' started by Graeme - CZ, Aug 26, 2020.

  1. Graeme - CZ

    Graeme - CZ
    Z Club Member

    Hi all,

    I'm thinking ahead to a possible job for next year - fix my whining diff. To those of you who have already done this fix, I'm curious as to how I should approach this. Do I a) remove diff and refurbish it or b) replace it with something else?

    If it's a) refurbishment, what parts do I need to cary this out?

    Any help / tips gratefully received.

    Regards, Graeme

    PS. Car is '73 US import. Not entirely sure which type of diff it is I have.
     
  2. Rob Gaskin

    Rob Gaskin Treasurer Staff Member Moderator

    You wont be able to do your diff yourself. Firstly I would ask on here for a good replacement.
     
  3. jonbills

    jonbills
    ZClub Administrator
    Staff Member Moderator

    you can always go with option c, learn to love the whine.
     
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  4. Graeme - CZ

    Graeme - CZ
    Z Club Member

    Agreed, I did not think it was something I would be able to attempt myself. So is it the sort of thing you have to send away somewhere to get done?
     
  5. Graeme - CZ

    Graeme - CZ
    Z Club Member

    It does tend to lesson after a while. So, on that. The whine per say is not causing any major damage; i.e. my diff is not about to explode whilst I'm on the motorway at 70mph? hmmm, and my new, louder exhaust may mask it somewhat.
     
  6. AliK

    AliK
    Z Club Member
    Staff Member Moderator

    So to offer a different perspective:

    Firstly, not knowing your level of mechanical knowledge, here are some good reads ...


    https://www.knowyourparts.com/technical-resources/drive-train/diagnosing-differential-noise/

    https://fuelandfriction.com/weekend-warrior/understanding-rear-differential-noise/

    https://itstillruns.com/causes-rear-end-whine-8454488.html

    Diff whine comes in different varieties and depending on which type you have, you get clues as to what is causing it.

    Diffs are not complicated but are precision devices in some respects.

    In simple terms typical whines come from:

    Lack of lubrication (have you changed / checked the lube?)

    Worn bearings

    Preload and / or backlash being out

    Worn gears - although I would say this is generally unlikely with a stock engine (unless your car has done 300k miles and or been very abused). These diffs are pretty hardy. The spider gears in the R180 are the weak points but that shouldn’t introduce whine.

    My advice is: having checked that there is enough lubricant in there, figure out in what conditions you are getting the whining.

    Take the diff off if you are able to do it yourself and spend a little time on a work bench with some “engineering blue” and ascertain the wipe pattern. This will tell you a lot.

    https://www.ebay.co.uk/itm/371441149605


    This is a healthy diff that is currently on my car ...


    [​IMG]

    Test the pinion pre-load. My old diff with probably 200k miles under its belt has 1-1.2kg of pre-load. New 3.9 diff with 100k had 3.2kgs and makes zero noise BTW!!!

    [​IMG]


    Then if you are comfortable with using a DTI gauge, you can measure backlash.

    So a good starting point is seeing how loose the diff is. Sometimes a preload adjustment will cure a lot of the whine.

    Finally, the problem is, whatever unseen diff you buy is a roll of the dice. I can pretty much feel how healthy a diff is by hand - I have 3 in my garage.

    If you need to buy bearings and seals, go to rockauto.com. Replace the seals if you have the diff out.

    Removing the diff can be tricky but with some luggage straps and a normal jack mine went on and off easily ...

    [​IMG]

    Other than that, as Jon says, the whine is something that takes me back to sitting in the back seat of my dad’s car in the 70s listening to the whine at motorway speeds. Something very retro about it! ;)
     
    Last edited: Aug 26, 2020
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  7. Graeme - CZ

    Graeme - CZ
    Z Club Member

    Thanks Alik. I’ll study that all in detail. G


    Sent from my iPhone using Tapatalk
     
    AliK likes this.
  8. stuart barrie

    stuart barrie
    Z Club Member

    If you wish to check backlash I have DTI gauge assess wear when rear end is getting coilovers done.
     
    AliK likes this.
  9. Graeme - CZ

    Graeme - CZ
    Z Club Member

    Sounds like a good plan.


    Sent from my iPhone using Tapatalk
     
  10. Albrecht

    Albrecht Well-Known Forum User

    You might want to take the opportunity to change to a more sporting final drive gear ratio at the same time. A manual transmission 1973 North American market 240Z would have been fitted with a 3.364:1 gear ratio, in comparison to the 3.9:1 ratio fitted in other markets.

    Maybe consider looking for a 3.7 or 3.9 as an alternative?
     
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  11. AliK

    AliK
    Z Club Member
    Staff Member Moderator

    Alan makes a great point. I just went from a 3.54 to a 3.9 and even that 10% change is noticeably more giggle inducing, but cruising revs are still sensible.

    Going from a 3.36 to 3.9 is a c.15% change and you will definitely enjoy the car more.
     
    Graeme - CZ likes this.
  12. jonbills

    jonbills
    ZClub Administrator
    Staff Member Moderator

    hard to be sure without hearing it, but I think it's unlikely to be dangerous. many people have had them rebuilt only to find they still whine.
     
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  13. AliK

    AliK
    Z Club Member
    Staff Member Moderator

    That’s also a great point. [emoji106]

    As Jon says, difficult to tell without hearing but I would wager that a whine which gets better with heating may well be bearings or lack of lube related.

    At the end of the day, this is not black magic and there are not that many variables; it’s pre-load, backlash, bearings or worn gears. So a careful or experienced rebuild should be able to eliminate or recommend a new diff of wear is the issue.

    There are horror stories of diffs rebuilt by Quaife packing up soon after or even some experienced mechanics / shops who have rebuilt them have had issues. It’s always worth double checking wipe, backlash and preload yourself no matter who has built it. Also some people have gotten swarfs / dirt down the pinion shaft which caused issues soon after a rebuild.

    From what I’ve read, disturbing the pinion is the thing that “appears” to be the root of all evil when rebuilding these diffs.

    On my diff I flushed with some engine oil I don’t plan on using, drained it completely by standing the diff crown wheel down in a bucket for a couple of days, then spent an hour or more meticulously cleaning out the inside with microfibre cloths and vacuuming to ensure no dust particles remained. Call me fussy, but I sleep better knowing it’s been wiped cleaner than my a...
     
  14. Rob Gaskin

    Rob Gaskin Treasurer Staff Member Moderator

    I've been told banana skins are good for reducing whine. ;)
     
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  15. stuart barrie

    stuart barrie
    Z Club Member

    I believe the diff already installed is R200 not checked ratio.
    As the engine is L28 entire drive train probably from 280Z
     
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  16. AliK

    AliK
    Z Club Member
    Staff Member Moderator

    Three things my car has taught me:

    1. Assume nothing!!! Check it for yourself.

    2. Trust nothing the PO ever did. Their standards and yours will be divergent.

    3. Take the time to get to know the car before rushing to buy stuff. You’d be surprised how the car takes you / your project in a different direction to that which you assumed it would!


    Case in point on no.3, I started with a small bit of play in the steering to fix; ended up taking apart and returning the entire front and rear axles + fuel tank etc!! 300+ hours later, the car is awesome!!! But I never did the exhaust and tuning changes I had planned for this summer. ;)
     
  17. Graeme - CZ

    Graeme - CZ
    Z Club Member

    It’s got fresh oil, so I guess likely to be bearing related. Any tips on where you’d even source a replacement, or is it more a case of refurbishing / upgrading what you have? Of where you can send one. Anyway, more investigating to be done on that before i consider anything. Don’t want to replace stuff, that I otherwise don’t need to.

    ...and thanks for all your help Stuart, very much appreciated.


    Sent from my iPad using Tapatalk
     
  18. AliK

    AliK
    Z Club Member
    Staff Member Moderator

    They come up through the club and often on eBay. What you have to consider is, unless you are confident about the history of what is being sold, it may be no different to yours.

    My vote is unless it’s really bad, live with it for a while and do some homework / naval gazing before spending.
     
    Graeme - CZ likes this.
  19. Graeme - CZ

    Graeme - CZ
    Z Club Member

    I’ve been thinking about this a bit more. I’ve got the whole backend stripped down at present to install my BC coilovers, plus do wheel bearings and u-joint spiders on the half-shafts. Would not be a massive leap to pull out the diff whilst i am at it. I’m just wondering if anyone knows of someone i could take it or send it too? I live in Edinburgh, so ideally looking for a someone up north.
     
  20. arcdef

    arcdef
    Z Club Member

    Out of interest could a different oil cause the diff to whine? I changed mine recently to manoil (cheap but had good reviews) and after it had more noticeable whine when driving.
     

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