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What should a recon diff feel like before fitting?

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    Originally posted by kryten View Post
    No it doesn’t - needs to go back to the vendor.

    also it sounds like the diff carrier bearings have been set up badly to generate lots of heat - despite the sun/planets shimming being wrongly set, it shouldn’t whine or get particularly hot.

    In a straight line the diff section isn’t ‘rolling’ so is doing nothing and therefore not generating heat (unless your back tyres are 2 different sizes, which I doubt)

    You got a bad one.
    I’ve heard good things about Fitchetts too
    I know what Fitchett puts in his axles, cos Tony told me when he was alive.

    As for the stuff above -sorry most of it is wrong.
    I have rebuilt loads of BRAND NEW old stock axles from the factory inc those for TR6 etc.
    You can't turn the planet gears PERIOD, or usally will be dead notchy if you can.

    IDEM Jaguar ones I have been recently rebuilding with all new bits...brand new stuff, made in Birmingham.

    Also as for carrier preload there is a proper setting for it.
    Did you know it's 3 thou, but makes little difference if you wind it up to 5.
    It won't and can't generate large losses even if you like that theory for the simple reason it's only going round at a few 100RPM max compared with the pinion which is going round at 1000s and 1000s....

    As for power losses in diffs there IS a big loss in a straight line and almost none extra on corners, simply because a hypoid pinion is a cross between a spiral bevel and a worm gear. Hypoid oil is used precisely because the forces are sliding and generate a lot of friction.
    Friction = heat.

    The power losses on run down are a lot higher which is why they put thrust buttons on trucks to give the pinion a helping hand under run down loads especially when using a TELMA.

    Just saying....
    Oh and btw the main reason why repro gears are noisy for stags is cos they've been made wrong...but hey you knew that didn't you??
    Last edited by down_the_plug_hole; 8th October 2017, 15:16.


      The 'notchy' diff, when fitted and with the road wheels attached felt quite smooth with that extra bit of momentum from the wheels. This was both out of gear so the wheel rotated the same way, turning the prop shaft, and in gear, so the wheels contra-rotated against a stationary prop-shaft. On the road, there is just a slight whine when pushing a lot of power through, otherwise silent.

      Two days of hard work, those damn exhaust pipes took some wrestling with, as did balancing the diff to offer it back up. We wanted to celebrate by shooting off up the nearest mountain, but the car had other plans and mischievously dumped her coolant. We suspect the system was air-locked on the last fill, we're not sure yet. We made it to the bar half way up the mountain, and span out a couple of beers waiting for everything to cool down, in the glorious sunshine.

      Thank you all for your advice on this job.