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Thread: I'd like to understand the D4 tranny??

  1. 13th August 2016, 09:06 PM #1
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    Milton477
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    I'd like to understand the D4 tranny??

    I'm curious as to how the torque converter in front of the 8 speed works. Does it lock & when, in which gears? Which gears are preferable for long climbs while towing? Just trying to understand what's happening so that I can maybe look after it a bit better.

    Last week I dragged 2600kg of caravan up Cunninghams Gap at the posted speed limits with my D4. Compared to the previous time with my D2, this last experience was, well, underwhelming. Nothing got hot, no alarms sounded & I found myself wondering where the hilly bit had gone to.

    The day was cool at 22 deg. The radiator temp got to 104, gearbox sat just under 100 & the engine oil ran at 125. I have towed with the D4 for 10k km & compared to the D2 the gearbox temperature seems to stay between 80 & 95 deg.

    It has been suggested to me that when the tranny is serviced at 40k & the sump replaced, I should fit an oil cooler. I'm wondering why when I look at how little the tranny temperature fluctuates compared to the D2. What will the temperatures look like on a 40 deg day? Has anyone fitted an additional oil cooler?

    Thanks
    Rory
    + 2016 D4 TDV6
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  2. 13th August 2016, 09:08 PM #2
    Tombie Guest
    Locks in ALL gears and completely decouples at idle...

    No need for any changes other than service, oil and steel pan...
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  3. 13th August 2016, 09:09 PM #3
    Tombie Guest
    As for hill climbing - chuck it in sports mode, makes it a bit more responsive....

    And if you choose, paddle down one up a hill..
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  4. 13th August 2016, 09:23 PM #4
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    Milton477
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    Thanks Tombie, that's precisely how it's been driven so far. Compared to my D2 with chips & bigger intercooler etc etc, it tows so effortlessly.
    + 2016 D4 TDV6
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  5. 13th August 2016, 11:34 PM #5
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    cjc_td5
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    You can't get a steel pan conversion for the 8 speed yet????
    If you can please let me know as my MY14 has done 70,000km and I want to change the oil at the next service.
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  6. 14th August 2016, 01:57 PM #6
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    LRD414
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    Quote Originally Posted by cjc_td5 View Post
    You can't get a steel pan conversion for the 8 speed yet????
    If you can please let me know as my MY14 has done 70,000km and I want to change the oil at the next service.
    I'm interested in this too for the 8 speed but sump conversion doesn't seem to be common.
    For example, this quote regarding the 8-speed from Robbie, who is a well regarded Disco mechanic in the UK and active on Disco3:
    Quote Originally Posted by Robbie UK View Post
    If there is a mechanical issue with the box or a repair to the mechatronic then I would change the filter.
    If it is just an additional oil change then the filter can stay put.
    With regular oil changes I'd be happy to run with the original filter until 150,000 miles / 10 years.
    Outside of a big mechanical failure I have yet to see a degraded filter.
    He has posted a guide to changing the fluid on Disco3, which appears reasonably straightforward albeit not a full flush.

    Regards,
    Scott
    D4 TDV6 MY14 with Llams, Tuffant Wheels, Traxide DBS, APT sliders & protection plates, Prospeed Winch Mount w/ Carbon 12K, Mitch Hitch & Drifta Drawers
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  7. 14th August 2016, 05:22 PM #7
    dalil
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    I got service done two weeks ago by Pickards automotive in Melbourne at 69k and out of this 10k towing 2.7t caravan.
    For around $960 i got new metal sump flush gearbox washed car and loan car.
    I did this service only ones off, next year i will do the same as Robbie, drain and refill as much as got out. I did this on my previous car (Prado) and at 380k gearbox fill as new. I don't know how good is oil cooler in disco4 , but on prado i add one from holden.
    TDV6, MY13, ARB bar, Led bar
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  8. 14th August 2016, 06:03 PM #8
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    LRD414
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    Quote Originally Posted by dalil View Post
    I got service done two weeks ago by Pickards automotive in Melbourne at 69k and out of this 10k towing 2.7t caravan.

    For around $960 i got new metal sump flush gearbox washed car and loan car.
    That's pretty good value. Is yours an 8 speed?

    Scott
    D4 TDV6 MY14 with Llams, Tuffant Wheels, Traxide DBS, APT sliders & protection plates, Prospeed Winch Mount w/ Carbon 12K, Mitch Hitch & Drifta Drawers
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  9. 14th August 2016, 06:37 PM #9
    dalil
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    Yes 3L TDV6 MY13 is 8 speed gearbox.I think thats when LR start ZF 8 speed.
    TDV6, MY13, ARB bar, Led bar
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  10. 15th August 2016, 05:20 PM #10
    PeterJ Guest

    A bit more info for the tech minded

    Hi, so I had my trans serviced at Solitaire (Adelaide dealer) for $908.03 so by all counts not so bad. Vehicle had done 52K about 60% towing 3.2t van.
    I noticed an improvement post oil change in shift quality but I am now at 66K and it is not as smooth as it was. I am still nervous about it's durability but I guess it's a waiting game.


    If you want some more technical info on the trans, look here Saturation Dive: The ZF 8HP 8-Speed Automatic Transmission

    Have done a bit of data collection while towing and found oil temps usually in the low to mid 90s, even pulling up extended grades it seems to cope really well.
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