# 2/4wd switching mech



## The Mad Hat Man (Oct 3, 2006)

Does anyone have a simple (coz its for me) description of how the 2/4wd switching mechanism works and how it operates?

I know the freelander uses a viscous coupling which is permanently engaged - how do Nissan do their switchable system?


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## ValBoo (May 19, 2003)

This is an extract from ESM:


System Description 
ELECTRIC CONTROLLED COUPLING
Operation principle
1. 4WD control unit supplies command current to electric controlled
coupling (4WD solenoid).
2. Control clutch is engaged by electromagnet and torque is
detected in control clutch.
3. The cam operates in response to control clutch torque and
applies pressure to main clutch.
4. Main clutch transmits torque to wheels according to pressing
power.
_ Transmission torque to rear wheels is determined according
to command current.

4WD CONTROL UNIT
_ Controls distribution of drive power between front-wheel drive
(100:0) and 4WD (50:50) conditions according to signals from
sensors.
_ Self-diagnosis can be done with CONSULT-II.

ALL MODE 4X4 SYSTEM
4WD MODE SWITCH
AUTO mode
_ Electronic control allows optimal distribution of torque to front/rear wheels to match road conditions.
_ Makes possible stable driving, with no wheel spin, on snowy roads or other slippery surfaces.
_ On roads which do not require 4WD, it contributes to improved fuel economy by driving in conditions close
to front-wheel drive.
_ Sensor inputs determine the vehicle's turning condition, and in response tight cornering/braking are controlled
by distributing optimum torque to rear wheels.
LOCK mode
_ Front/rear wheel torque distribution is fixed, ensuring stable driving when climbing slopes.
_ Vehicle will switch automatically to AUTO mode if vehicle speed increases. If vehicle speed then
decreases, the vehicle automatically returns to direct 4-wheel driving conditions.
_ LOCK mode will change to AUTO mode automatically, when the vehicle speed exceeds approx. 30 km/h
(19 MPH). The LOCK indicator light keeps illuminating.
NOTE:
If there is a significant difference in pressure or wear between tires, full vehicle performance is not available.
Tire conditions are detected, and LOCK mode may be prohibited, or else speeds at which LOCK mode is
enabled may be restricted.
2WD mode
Vehicle is in front-wheel drive.
NOTE:
_ If front wheels are slipping in 2WD mode, do not switch to AUTO or LOCK. This can cause difficulties for
the system.
_ Even if the 4WD mode switch is in 2WD mode, the 4WD control unit occasionally automatically change to
AUTO mode depending on the driving condition (For example; Depressing the acceleration firmly). This is
not malfunction. However, 4WD indicator lamp dose not illuminate.


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## The Mad Hat Man (Oct 3, 2006)

brill, Valboo.

any pics
I know its a daft idea - but trying to sort out a 2/4wd switch system for a freelander and am looking at wot other vehicles use, to see if it can be grafted on


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## Rockford (Jan 28, 2005)

"Even if the 4WD mode switch is in 2WD mode, the 4WD control unit occasionally automatically change to AUTO mode depending on the driving condition (For example; Depressing the acceleration firmly). This is not malfunction. However, 4WD indicator lamp dose not illuminate."

Huh? So, if you floor it in 2WD the rears will still engage?


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## roj1943 (Aug 10, 2006)

The Mad Hat Man said:


> brill, Valboo.
> 
> I know its a daft idea - but trying to sort out a 2/4wd switch system for a freelander and am looking at wot other vehicles use, to see if it can be grafted on


Hi Mad Hat Man. Used to live in B'stoke myself. Don't waste your time converting a Freelander's 2/4wd system. There is a coupling in the propshaft containing a viscous fluid that get more viscous when heated by the friction caused when the front and back axles rotate at different speeds. This sends more power to the rear axle. There are no controls, electric or otherwise, involved. This system actuates on my Freelander when turning a slow tight corner (parking, for example) so that the engine can stall if I don't use a little more throttle. The X Trail system does not suffer from this and would be a far better idea, but I imagine that the amount of engineering needed to convert a Freelander would make the project beyond the resources of any DIY enthusiast.

Unless, of course, you are a millionaire with a fully equipped workshop . . . ? 

Incidently, If I accelerate too hard in my X Trail (in 2wd), the rear wheels do not kick in, the front ones simply spin, despite what my vehicle handbook says. In 4wd, of course, there's no spin.

Have fun and everything
Roger.


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## ValBoo (May 19, 2003)

Rockford said:


> "Even if the 4WD mode switch is in 2WD mode, the 4WD control unit occasionally automatically change to AUTO mode depending on the driving condition (For example; Depressing the acceleration firmly). This is not malfunction. However, 4WD indicator lamp dose not illuminate."
> 
> Huh? So, if you floor it in 2WD the rears will still engage?


Thats what it says although I have yet to see this happen...


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## The Mad Hat Man (Oct 3, 2006)

Hi Roj
sorry folks - i know this is a Nissan forum

I am aware of the VCU (and its many probs on the Hippoo(freelander)) hence the prospect of having a mechanical system rather than the [email protected] VCU is very attractive. I am an active participant on Landyzone - One of the most usual mods is to remove the VCU/propshaft and use it in 2wd mode during summer. Other peeps are looking into dog-clutch systems etc. I am just interested in how the X-T system works and whether it could be adapted/plagarised for use on the Hippoo. Cost is irrelevant at this stage - it is ideas and practicalities which are useful.
Thanks Valboo for above info, but I am more into the mechanical system at the mo ......
where is the "electrical controlled coupling"?
control clutch?
main clutch?


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## roj1943 (Aug 10, 2006)

As the X Trail 2/4wd clutch is electrically powered (either voltage or current, I have no wiring diagrams for it), a meter in the circuit would indicate the voltage (or current) being fed to the clutch thus giving an indication of the amount of power being transferred to the rear axle.

Wouldn't it?  

If this worked, it would make a nice display on the dashboard.

Roger


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## Ice512 (Oct 16, 2006)

roj1943 said:


> As the X Trail 2/4wd clutch is electrically powered (either voltage or current, I have no wiring diagrams for it), a meter in the circuit would indicate the voltage (or current) being fed to the clutch thus giving an indication of the amount of power being transferred to the rear axle.
> 
> Wouldn't it?
> 
> ...



wooahhh that would be SWEEEEEEEEEET..just like the new MDX with the SH AWD, with a diagram on the dashboard showing power distribution.


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## LEONGSTER (Apr 9, 2006)

The Mad Hat Man said:


> Hi Roj
> sorry folks - i know this is a Nissan forum
> 
> where is the "electrical controlled coupling"?
> ...


The electromagnetic coupling on the XY sits just ahead of the rear differential case, after the prop shaft. 

This is the 'control' clutch if you will. The main clutch sits where it mostly does - at the flywheel.

The beauty of the XY's system is that I believe it works rather like an electromagnetic 'brake' to control the torque fed to the rear differential case. 

The flipside of this is that you'd still need electronics to control the coupling. Unlike the Freelander's VCU, the XY's is not a purely mechanical system.


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## The Mad Hat Man (Oct 3, 2006)

brill - wunda if it would work on its own (with electrics of course)


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## LEONGSTER (Apr 9, 2006)

The Mad Hat Man said:


> brill - wunda if it would work on its own (with electrics of course)


If you don't mind forgoing the variable torque output feature then you could always rig a simple dashboard relay switch that feeds the required current directly to the coupling. This may be how the "lock" switch on the XY works but I am just guessing.


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## The Mad Hat Man (Oct 3, 2006)

does anyone have a copy of the circuit diagram for this system?
if so - wud they like to post it here.

or a photo of this rear unit 




please


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## The Mad Hat Man (Oct 3, 2006)

any idea on prices of this rear clutch unit? (in gbp)


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## The Mad Hat Man (Oct 3, 2006)

does anyone know if the rear clutch would work with a simple switch to supply 12v to the solenoid. I know that normally it is controlled by the 4wd controller, but i need a simple activator for use on a project.


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## roj1943 (Aug 10, 2006)

The Mad Hat Man said:


> does anyone know if the rear clutch would work with a simple switch to supply 12v to the solenoid. I know that normally it is controlled by the 4wd controller, but i need a simple activator for use on a project.


Hi Mad Hat, take care if putting 12 volts onto the rear clutch. I think that this is a current operated device, not voltage. If this is so, you MUST limit the current. I have a vague memory of 2 point something amps being mentioned. You would need a pot and an ammeter in series with your feed to the clutch as a minimum. You may also need to protect the output from whatever electronics controls the clutch. I saw an article mentioning this a week or so ago, but cannot remember where this was. I have searched but cannot find it. If I ever do, I will post the info. Old age is slowly getting me.
Have fun, and good luck with your project.
Roger.


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## LEONGSTER (Apr 9, 2006)

The Mad Hat Man said:


> does anyone know if the rear clutch would work with a simple switch to supply 12v to the solenoid. I know that normally it is controlled by the 4wd controller, but i need a simple activator for use on a project.


Check out the schematic on the electronic coupling here: 

AutoSpeed - Nissan's New Engineering

It appears to be a multiplate clutch (like a motorcycle's) attached to an electromagnet. You'd need to determine the type of current with an o-scope.


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## roj1943 (Aug 10, 2006)

Hi Mad Hat,

It's a great shame that no-one seems to know exactly what is going on in the darkest depths of the X-Trail's entrails. The people at Nissan (who presumably read these forums - fora?) must be spilling their beer with laughter at times.

I've looked at Leongster's note and he comments elsewhere that there is the possibility that a pulse width system could be used.

OK. Unless you know your electronics, that will be of no help to you in making a simple actuating system. What you could try is a slight modification of your idea of sticking a 12v feed on to the device (AT YOUR OWN RISK!!!).

A length of 10A (minimum) insulated wire from the battery (don't connect it yet) via a 3A line fuse (very important, it protects the wire and helps stop fires and burnt hands) to a DC ammeter that will read up to about 5 amps. Cheap multimeters may not have that range. From the ammeter, still in 10A wire, to a variable resistor (rheostat) capable of handling at least 5 amps. This variable resistor will be big 'cos it may need to dissipate 120 watts or more. From there to the clutch unit making sure that the resistor is turned to maximum. 

Disconnect the existing feed to the clutch to avoid potential damage to the control system.

If you are brave enough, connect to the battery and observe the clutch unit as you increase the current. Watch for smoke/sparks/melted metal and the like. Do not go above about 2 amps. This is at your own risk, remember.

Nissan would not use a system like this 'cos of the physical size of the bits and the difficulty of achieving good control which is why they may indeed use a pulsed system of some kind.

Best of luck, let us know if you and the car survive this.

Roger.

PS. I'll be in Basingstoke on Saturday, a couple of hundred yards from Sainsbury's at Hatch Warren. I'll look for a column of smoke. Have fun.


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## The Mad Hat Man (Oct 3, 2006)

Hi Roj
Thanks for info. I am having discussions with local auto sparks to try and ascertain current used on the rear clutch. 
I will NOT be trying it on mine  so if anyone wants to offer an old rear clutch/diff assembly for me to play with i will be grateful
or if anyone wants to wire up an oscilloscope.......
at the mo , my main concern is the physical fitting of the device:idhitit: , and where to cut through the diff casing. The electronics are a second problem. It might even be possible to use the 4wd control unit with dummy inputs:woowoo: . (anyone know?)

once again thanks for all your input- it is appreciated.


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## The Mad Hat Man (Oct 3, 2006)

Hi Roj
Thanks for info. I am having discussions with local auto sparks to try and ascertain current used on the rear clutch. 
I will NOT be trying it on mine  so if anyone wants to offer an old rear clutch/diff assembly for me to play with i will be grateful
or if anyone wants to wire up an oscilloscope.......
at the mo , my main concern is the physical fitting of the device:idhitit: , and where to cut through the diff casing. The electronics are a second problem. It might even be possible to use the 4wd control unit with dummy inputs:woowoo: . (anyone know?)

once again thanks for all your input- it is appreciated.


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## LEONGSTER (Apr 9, 2006)

roj1943 said:


> I've looked at Leongster's note and he comments elsewhere that there is the possibility that a pulse width system could be used.


Uh, actually I edited out that suggestion for fear that Mad Hat would get the wrong idea and end up blowing his transmission, LOL.

Honda have a patent on a similar clutch design that uses a pulse generator to actuate the system (in fact several electronically controlled clutches were patented as far back as the 70s).

In the XY Nissan probably thought they'd use it as a testbed for every bit of innovation they could think of - to our gain.


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## The Mad Hat Man (Oct 3, 2006)

oh no! - nuffink gets touched on MY mota  - its early days, but the Nissan system seems far betta than any other I have looked at so far.
I haven't asked before - but there aint any "issues" with this system - are there?


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## LEONGSTER (Apr 9, 2006)

I try to use the 4x4 function at least once a week in 20-30km of driving even though there may not be a need for all-wheel drive. (Since I'm a staunch believer that mechanical stuff needs to be exercised.)

As for reliability issues, maybe you could ask the chaps that actually_ built_ these things, or even get them to sell you a couple sets LOL.

Check out:

http://www.jtekt.co.jp/e/products/drive02.html


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## The Mad Hat Man (Oct 3, 2006)

fantastic - thanks for link - will contact them.


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