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Thread: Front Diff

  1. #1
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    Front Diff

    I have been chasing a faint moan under load for a while (No unhappy passengers )
    Found the pinion shaft of the front diff was loose. the bolt holding the flange was tight, so I am assuming a pinion bearing has failed, so diff rebuild coming up.

    Problem is I can't find any information on the front diff assembly in any of the manuals I have. The only reference in one of them (for a LR90) says 'contact Land Rover for advice' ??
    I don't know if the pinion is shimmed or has a collapsible spacer, The pinion end looks nothing like any other Rover diff I have seen. There is a bolt holding the flange on instead of the usual nut.

    I really need preload data at least, does anyone know where I might find that?

    Thanks,
    Terry
    80 109" 2.6 P ex Army GS, saved from the scrappie.
    95 300tdi 130 Single cab tray.
    2010 Guzzi 750

  2. #2
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    I found this on the ashcroft site:

    Ashcroft Transmissions

    I reckon you can probably send them an email, they should have any data you might need

    -P

  3. #3
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    The pinion is shimmed, basically the same setup as ye olde Rover diff . There is a tube between the pinion bearings but not a crush tube, just a spacer.
    The bolt is cheaper to manufacture than the nut method, Later rover diffs use the bolt as well as the P38. makes no difference to setting it up.
    Last edited by goingbush; 3rd May 2019 at 10:05 PM.

  4. #4
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    Quote Originally Posted by rover-56 View Post
    ....
    I really need preload data at least, does anyone know where I might find that?

    Thanks,
    Terry
    Assuming you have RAVE? And have the Range Rover section open ...

    If so, look for the section marked 51/Rear Axle and Final Drive/Oil Seal-Pinion.
    Only repair info is on removing the final drive and also replacing the pinion seal .. nothing on the actual final drive repair at all.
    Anyhow, on the pinion page you see that they have the two options for securing the pinion flange .. ie. both nut type and bolt type.
    Torque specs for each are 100Nm for the bolt type, 135Nm for the nut type.
    A lot of the specs are the same as for the D1 and D2 diffs .. makes sense as already said same diffs.
    D1 uses the nut type, D2 uses the bolt type .. same torques.

    For some reason tho, they seem to have no repair data on the final drive at all(that I can see) in the P38 area, whereas on the D1/D2 repair manual area, they do.

    In the D1/D2 manual tho, the front diff repair info is all based on the rear diff specs. Saves repeating oneself! so for the front diff, look for the rear diff specs.
    D1 and D2 are slightly different, but you would assume the D2 diff data would be a closer match for a P38.

    Anyhow, it'd be safe to assume that as you have a bolt type, then this would equate to the D2 type diff specs.
    Pinion bearing preload is 4-6Nm turn on the pinion.
    There's no data on any difference between new bearings and old, so assumption is that this is for both.
    This is mentioned because in the D1 diff section they do list a difference. FWIW D1 data says 3Nm preload(new bearings) and 1.5Nm using the old bearings.
    Moot point considering you'll be renewing the bearings anyhow.
    Arthur.

    '99 D1 300Tdi Auto
    '03 D2 Td5 Auto

  5. #5
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    Quote Originally Posted by goingbush View Post
    The pinion is shimmed, basically the same setup as ye olde Rover diff . There is a tube between the pinion bearings but not a crush tube, just a spacer.
    The bolt is cheaper to manufacture than the nut method, Later rover diffs use the bolt as well as the P38. makes no difference to setting it up.
    Thanks Don. Yes I was planning to use the Series info if nothing else found, but Arthurs post (thanks Arthur) reminded me I still have the D2 Rave CD somewhere - didn't think of that.

    Happily the viscous clutch is happy to drive the RR around with the front tailshaft off, so no panic here.
    Thanks guys, should be fun - haven't done a diff rebuild for about 15 years.

    Cheers,
    Terry
    80 109" 2.6 P ex Army GS, saved from the scrappie.
    95 300tdi 130 Single cab tray.
    2010 Guzzi 750

  6. #6
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    Quote Originally Posted by rover-56 View Post
    Thanks Don. Yes I was planning to use the Series info if nothing else found, but Arthurs post (thanks Arthur) reminded me I still have the D2 Rave CD somewhere - didn't think of that.

    Happily the viscous clutch is happy to drive the RR around with the front tailshaft off, so no panic here.
    Thanks guys, should be fun - haven't done a diff rebuild for about 15 years.

    Cheers,
    Terry
    If you've done diffs before its like falling off a bike, just do it by feel and bearing blue. If you use the same bearing type and reuse the existing shim to set the pinion height as is already there it should be OK .

  7. #7
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    Yes too easy. nearly came off the bike last week dodging a bloody suicidal wallaby.
    80 109" 2.6 P ex Army GS, saved from the scrappie.
    95 300tdi 130 Single cab tray.
    2010 Guzzi 750

  8. #8
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    There are some great you tube videos on the Ashcrofts website re setting up diffs and also about pegging.
    I am about to peg my front and rear diffs after my front diff stripped teeth from the ring.
    If the bolt is tight you shouldnt have any sideways looseness in the pinion.
    If you excessive backlash i would be checking the diff and see what is occuring.

    Ian
    Bittern

  9. #9
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    Thanks Ian, yes I will be stripping the diff to have a look.
    I am curious to find out why when the flange bolt is tight the flange is still loose on the splines.
    Won't get to it for a couple of weeks though, will be relying on the S3 for a while.
    Cheers,
    Terry
    80 109" 2.6 P ex Army GS, saved from the scrappie.
    95 300tdi 130 Single cab tray.
    2010 Guzzi 750

  10. #10
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    Well, finally got back to the diff, pinion bearings arrived.
    Drained the oil and found this.

    Big tick to Rover for using magnetic drain plugs.

    No shims on the pinion shaft except the big one behind the inner bearing.
    The new bearings (Timken, same as came out) produced a torque to turn slightly less than spec, 2 lb/ft. can't increase that without grinding a bit off the spacer, which I can't do. Going to leave it as is.
    Don't know why the bearings failed, although someone has been in there before me judging by the amount of black silastic on the the housing.
    Diff carrier and crownwheel tomorrow, can't check the pinion height, I don't have the tools. Will have to rely on gear tooth marking. Should be ok anyway.
    Terry
    Tried to insert the pics into the text area, don't know why I can't.
    Attached Images Attached Images
    80 109" 2.6 P ex Army GS, saved from the scrappie.
    95 300tdi 130 Single cab tray.
    2010 Guzzi 750

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