Range Rover 3.9L 1990





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  1. #1
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    Default Range Rover 3.9L 1990

    Good morning folks,

    My dad recently picked up a 1990 Range Rover Classic 3.9L four door with the Auto transmission. The car is in incredible shape and for a bargain of R60k on top of it all!

    we just have a couple of technical questions regarding the vehicle’s 4x4 system.

    My dad also owns a 1980 RRC 2 door from 1981 and it has permanent 4 wheel drive with a centre diff lock - but the new car only has the auto stick and the lever for the transfer case.

    As far as I can tell from reading tech specs online this car has a VCU that engages once traction is lost - does this mean that the car is basically 2WD that only kicks into 4WD AFTER losing traction? - seems a bit disappointing that in an RRC you cant lock it into 4WD before attempting an obstacle..

    or am I understanding it wrong?

    anyway the car is a beauty and has clearly never been off road - we’re planning to change the latter fact soon!
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  3. #2
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    Default Re: Range Rover 3.9L 1990

    That is such a deal !!!! You are so lucky !!

    Enjoy
    1997 Discovery 1 300tdi - Pussy Galore
    1996 Discovery 1 V8 - Mr Creosote

  4. #3
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    Default Re: Range Rover 3.9L 1990

    No it is in 4WD all the time. ie It drives all 4 wheels and has three diffs. One for each axle and one separating front and rear.

    The viscous kicks in when it detects slip between the front and rear and then you have an engaged CDL, or rather the equivalent of that.

    Its actually very clever and very very good. Because of the way it works it doesnt just engage for a second and then let go, but rather it is a gradual thing. It takes a fair bit of slip before locking and then stays locked for a while after traction is regained. So if you are in a situation of repeated traction/no-traction it basically, due to thermal inertia is sort of "ready" when you need it.

    You really need to see an exploded view of the Transfer case with VCU to understand it properly.

    The traction improvement, while not as predictable or as good as a manual CDL for Grade 4/5 impersonations of a mountain goat, is damn effective and essentially the driver is never aware of its operation, aside from the traction of course.

    -----------------------

    In a sense it is a bit like traction control, so it requires constant steady throttle to work best.
    Cheers

    ZS5KAD
    3 V8's
    NA TwinTurbo SuperCharger
    A V6 and an inline 4

    The frogs are starting to notice that the water is getting warm but it is already too hot to do anything about it.....

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  6. #4
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    Default Re: Range Rover 3.9L 1990

    Quote Originally Posted by Fluffy View Post
    No it is in 4WD all the time. ie It drives all 4 wheels and has three diffs. One for each axle and one separating front and rear.

    The viscous kicks in when it detects slip between the front and rear and then you have an engaged CDL, or rather the equivalent of that.

    Its actually very clever and very very good. Because of the way it works it doesnt just engage for a second and then let go, but rather it is a gradual thing. It takes a fair bit of slip before locking and then stays locked for a while after traction is regained. So if you are in a situation of repeated traction/no-traction it basically, due to thermal inertia is sort of "ready" when you need it.

    You really need to see an exploded view of the Transfer case with VCU to understand it properly.

    The traction improvement, while not as predictable or as good as a manual CDL for Grade 4/5 impersonations of a mountain goat, is damn effective and essentially the driver is never aware of its operation, aside from the traction of course.

    -----------------------

    In a sense it is a bit like traction control, so it requires constant steady throttle to work best.
    I too have old style 1981 2-door RRC ...
    ... if I can get hold of such front and rear diffs
    can I readily effectively use them and adapt to use as manually ‘invokeable’
    front and rear diff locks ?
    Last edited by BushNomad; 2019/10/06 at 10:53 AM.
    ... Land Rover Owners dont idle long ...

    2002 Defender 130 DC HCPU. : Own the road...Any road
    ‘1981 R-Rvr Classic 2-Dr 3.5L V8... The Greatest Rover.
    ‘1975 Series3 88 PUP... Simply Classic...
    ‘2017 Metalian Mini ... A Home from Home

    * The Monarch of the Glen *http://www.4x4community.co.za/forum/...1&d=1507751251

  7. #5
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    Default Re: Range Rover 3.9L 1990

    Quote Originally Posted by BushNomad View Post
    I too have old style 1981 2-door RRC ...
    ... if I can get hold of such front and rear diffs
    can I readily effectively use them and adapt to use as manually ‘invokeable’
    front and rear diff locks ?

    Hi,

    The Viscous lock I am talking about is in the "transfer case / centre diff"

    Your 1981 probably has similar, if not identical diffs to the 1990 in this thread.
    Cheers

    ZS5KAD
    3 V8's
    NA TwinTurbo SuperCharger
    A V6 and an inline 4

    The frogs are starting to notice that the water is getting warm but it is already too hot to do anything about it.....

  8. #6
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    Default Re: Range Rover 3.9L 1990

    Quote Originally Posted by Fluffy View Post
    Hi,

    The Viscous lock I am talking about is in the "transfer case / centre diff"

    Your 1981 probably has similar, if not identical diffs to the 1990 in this thread.
    Thanks ...

    ... but pity as my getting rid of Manual
    gear change , or the LT95 box for that matter, is just not negotiable ...

    ... when auto-transmission packs up in middle of nowhere its a nightmare ...
    ... one I witnessed 2 weeks ago ...
    Last edited by BushNomad; 2019/10/06 at 03:54 PM.
    ... Land Rover Owners dont idle long ...

    2002 Defender 130 DC HCPU. : Own the road...Any road
    ‘1981 R-Rvr Classic 2-Dr 3.5L V8... The Greatest Rover.
    ‘1975 Series3 88 PUP... Simply Classic...
    ‘2017 Metalian Mini ... A Home from Home

    * The Monarch of the Glen *http://www.4x4community.co.za/forum/...1&d=1507751251

  9. #7
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    Default Re: Range Rover 3.9L 1990

    Thanks for explaining it so clearly!

    wow, it sounds like a very good system - now I feel bad for doubting it, I clearly just didn’t understand it.

    It’s an incredible vehicle - just wish it were less thirsty.

    Twisting dad’s arm to take it to Tierkloof soon, not sure if my Freelander 2 will be up to the task to keep up though!

  10. #8
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    Default Re: Range Rover 3.9L 1990

    I had a 3.9l auto RRC and can confirm that in its STD form is an incredibly agile off roader on all terrain.
    I had absolutely no issues with it over many years, except to replace the fuel pump. Most probably because it has to pump so much!
    Lovely cars.
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  11. #9
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    Default Re: Range Rover 3.9L 1990

    Yip, also had one and I can attest to the beauty of the center viscous lock. Came into its own on muddy roads, sand, etc... I fitted mega jolt to mine, made the V8 more responsive and less thirsty. Mine was a manual low spec import model. Sold as it had no air con and long family road trips became unpleasant.

    I loved that Rangie!
    Dale
    F150 4x4 5.4 Triton V8
    Series 3 Land Rover 109 SW
    GU Patrol 3.0Di GL
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