Is this correct ?
- Thread starter thefrog
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saxavordian
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GrumpyGel
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Turboman
Mab An Gov
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What do you mean by permanent?
No "Four Wheel Drive" actually drives all four wheels all of the time. If it did, you wouldn't be able to steer., and would probably suffer transmission wind up in short order.
I don't know much about freelanders, but a Series in 4wd drives two wheels. A Defender with centre diff unlocked drives one and a bit wheels. But if you lock centre diff, it drives two wheels. Either vehicle, if fitted with a rear axle locker, will drive three wheels with everything locked up.
So a freelander probably never drives more than two wheels at the best of times, but I am sure a freelanderer will explain what it actually does later.
Turboman
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Much more complicated than my brain as well. I just whang the lever over, stick my foot down, and hope for the best!Its much more complicated than the sticker isnt it.
J
The Freelander is All Wheel Drive (AWD) which is different from 4 wheel drive. An AWD system allows for use on a road without damage to itself, as there's some slip between the axles, but 4WD there's no slip, so in this instance would fail very quickly.
As far as I am concerned (I don't own a FL) the FL is not a permanent 4WD. Although as above its complicated.
The FL does not have a positive fixing between front and back, the bit in the middle that connects is variable.
I am sure a FL egsquirt will be along to show me the error of my ways but hey ho.
J
The FL does not have a positive fixing between front and back, the bit in the middle that connects is variable.
I am sure a FL egsquirt will be along to show me the error of my ways but hey ho
.J
Really
If its locked front/back but then you have diffs left/right.
As I said its complicated.
J
GrumpyGel
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You're trying to be to clever there TM.
A Your description of a 4WD only driving 1 wheel is true, but its also true that a 2WD will only drive 1 wheel - so why have 4WD if its no better?
Because so long as they have equal traction, a 4WD will drive 4 wheels and a 2WD will only drive 2 wheels.
But, a lot of 4WD cars are switchable between 2WD and 4WD. As you say, Tratters (and Jap trucks etc) are switchable, but 90/110s and Defenders, like Disco/RR are permanent 4WD. That is why there are the terms 'switchable 4WD' and 'permanent 4WD'.
Freelander isn't 'permanent 4WD' , it doesn't have a center diff. It is AWD. This is an improvement over both permanent and switchable in that it guarantees drive to 2 wheels - without the need for a locker and the need to slow/stop to engage them.
RR Classic and P38 are an improvement over AWD as they are 4WD but with an automatically locking center diff, using the same viscous coupling method that Freelander uses for its AWD.
GrumpyGel
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My "Land Rover Transmission For Dummies" post, can be read with a lot of "ahh... buts".
Its where these discussions never end because the terms 2WD, 4WD, AWD, permanent, switchable blah blah are categorisations that can and are implemented in different ways.... and be open to interpretation.
Until you understand how things work, and what's involved/why, that's the key
Then even this Dummy (me) understands
.J
300bhp/ton
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Does the IRD do anything other than act as a front diff and transfer case? The VCU allows the vehicle to turn, i.e. front and rear wheels to spin at different speeds, while still being able to drive both axles. But does the IRD do any sort of fwd bias or torque split too?
In regards to the ops question, part time, full time or permanent are probably all poor ways to describe most 4wd systems. In the Freelander there is no 2wd option, therefore logically it can only be driving all 4 wheels all of the time. It is also a completely mechanical setup.
Other more modern SUV's and soft roaders may have electronic control to enable fwd only or automatic modes to vary the amount of rear wheel drive. Depending on how they do this and to what degree they might not be permanent 4wd setups, but they could be.
In regards to the ops question, part time, full time or permanent are probably all poor ways to describe most 4wd systems. In the Freelander there is no 2wd option, therefore logically it can only be driving all 4 wheels all of the time. It is also a completely mechanical setup.
Other more modern SUV's and soft roaders may have electronic control to enable fwd only or automatic modes to vary the amount of rear wheel drive. Depending on how they do this and to what degree they might not be permanent 4wd setups, but they could be.
Is it a mechanical connection front to back
.The 90 has a variable mechanical connection front to back, but it has 1 of those clever diff things
, But it also has a lever that makes a positive connection front to back. Which could give me 2wd in worse cases.Its simple for those that know and complicated for those that don't.
J
GrumpyGel
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It has kept engineering workshops in business for 20 years.
It does gear down the drive to the back axle by a fraction of a percent. The percentage changed over the lifetime of Freelander production.
In 'normal' driving, I'm not sure if this gives more torque to the front - as presumably being geared down, the rears would get more torque, but they wouldn't use it because the fronts have already moved the car.
GrumpyGel
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It is a physical connection for sure.Is it a mechanical connection front to back
Normally 99.999% of that physical connection are mechanical gears and prop shafts, but part of it is a viscous fluid. But when a wheel slips, immediately there is a 100% mechanical connection when the plates in the VCU 'lock up' (hump mode).
If you jack a back wheel up on Freelander, you can turn it by hand. But you need a lot of force and it will only turn very slowly.
300bhp/ton
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Well ok, technically a viscous coupling would be a "hydrodynamic device". But seeing as the system uses no ECU control, I think calling it a mechanical drive setup is not so wrong. As that was more the point I was making.Is it a mechanical connection front to back
The 90 has a variable mechanical connection front to back, but it has 1 of those clever diff things
Its simple for those that know and complicated for those that don't.
J
No, its not a physical mechanical connection, Does it actually have parts bolted/locked with a lever, together?
Ok so its a variable fluid connection
.J
