Rav 4 4.3

[vivianM]

Here is one for Kingo - bet you would sell a great many if you could find a chip? or whatever so that the 4 wheel drive cuts out at (say)35mph and not 23mph - you often need a bit more speed to get through drifts and it would be nice to know it is still in 4WD at that time also even up to 30mph it would be better - I assume it is part of the lowering of emission thing but a overide switch just to use when you need it would be great.

I think Anchorman told me that it does switch to 4WD if it senses a lot of wheel spin above 23mph. In that case does the 4WD light come on?

Guy

In a cold and snowy High Peak of Derbyshire this morning !

[Davrav]

Here is one for Kingo - bet you would sell a great many if you could find a chip? or whatever so that the 4 wheel drive cuts out at (say)35mph and not 23mph - you often need a bit more speed to get through drifts and it would be nice to know it is still in 4WD at that time also even up to 30mph it would be better - I assume it is part of the lowering of emission thing but a overide switch just to use when you need it would be great.

I think Anchorman told me that it does switch to 4WD if it senses a lot of wheel spin above 23mph. In that case does the 4WD light come on?

Guy

In a cold and snowy High Peak of Derbyshire this morning !

Hi Guy,

As far as I understand, the 4.3 RAV is a variable 4WD system that constantly monitors and adjusts the balance between front and rear wheels as required up to a maximum of 55/45% front to back.

Therefore there is no warning/information light normally on. It always starts in full 4WD and then increases balance to front wheels as conditions allow.

When you press the diff lock button it locks up the system [which is very sensitive].

I guess that, as speed increases, the system assumes traction has also been increased and the 'lock up' is not necessary and is switched off to avoid damage to the electro magnetic [i think] transmission.

Anchorman's much more thorough explanation is post 3 here: http://www.toyotaownersclub.com/forums/index.php?showtopic=117265

[Parts-King]

I hear what you are saying, but these RAV's are soft roaders and not true off roaders. There would not be many times a full, permanant four wheel drive would be needed, espacially above the 23 MPH threshold. I suppose they have to balance all of the cars capabilities/features/costs and arrive at a answer to suit most needs. Of course, should the snow become an all year round feature, maybe we could get Toyota to make a few changes

Kingo

[vivianM]

I hear what you are saying, but these RAV's are soft roaders and not true off roaders. There would not be many times a full, permanant four wheel drive would be needed, espacially above the 23 MPH threshold. I suppose they have to balance all of the cars capabilities/features/costs and arrive at a answer to suit most needs. Of course, should the snow become an all year round feature, maybe we could get Toyota to make a few changes

Kingo

Thanks Kingo and Davrav for your interesting comments! Still think 23mph is a bit too low

Guy

[Roadwrangler]

Here is one for Kingo - bet you would sell a great many if you could find a chip? or whatever so that the 4 wheel drive cuts out at (say)35mph and not 23mph - you often need a bit more speed to get through drifts and it would be nice to know it is still in 4WD at that time also even up to 30mph it would be better - I assume it is part of the lowering of emission thing but a overide switch just to use when you need it would be great.

I think Anchorman told me that it does switch to 4WD if it senses a lot of wheel spin above 23mph. In that case does the 4WD light come on?

Guy

In a cold and snowy High Peak of Derbyshire this morning !

If I understood Anchormans recent explanation to me, even above 23mph, if you put power on to accelerate or start sharp manouevering etc, the rear wheels instantly re-engage drive and then gradually step off the drive as the car becomes stable again. I would have thought between the VSC and Traction Controll we have, as soon as the Gyroscope detects the car heading sideways or a wheel sensor detects a difference in speed/rotation on the back wheels, the system will re-engage the back wheels whilst they are needed anyway.

Just a thought however, as the rear drive is electronicaly controlled, perhaps an override switch could be installed, forcing the rear diff to be perminantly engaged, someone with a better understanding of the wiring and electronics might be able to elaborate further there, nudge shcm

Regards Austin..

[Davrav]

I hear what you are saying, but these RAV's are soft roaders and not true off roaders. There would not be many times a full, permanant four wheel drive would be needed, espacially above the 23 MPH threshold. I suppose they have to balance all of the cars capabilities/features/costs and arrive at a answer to suit most needs. Of course, should the snow become an all year round feature, maybe we could get Toyota to make a few changes

Kingo

Thanks Kingo and Davrav for your interesting comments! Still think 23mph is a bit too low

Guy

Not sure I'd want to hit a drift at anything more than 23mph - there could be a broken Landrover under it

[rambler]

Bring on the 4.2 ,permanent 4wd...just needs a rear diff lock

[shcm]

nudge shcm

In the repair manual, available on the techdoc site, the control of the linear solenoid is shown as a pulse waveform. The linear solenoid effectively controls the clutch in the rear diff and therefore the amount of torque/drive to the rear wheels.

Back to the pulse waveform. It is not stated, but I suspect it is a "PWM" (pulse width modulator). For those that don't know, I'll have a go at explaining, but may not be very successful :D.

PWM is a standard technique for effectively generating a continually variable signal (or control), when you only have 2 states available (on or off). In a fixed time interval (and it looks like 4 ms for the solenoid control), an electrical pulse is generated. In theory, the width of the pulse is varied from no pulse at all (fully off), to a maximum pulse width of the time interval (4ms in this case - i.e. fully on). In fact for the fully on case, the pulse will no longer be a pulse, but just a permanent "on" signal. It can get more complex:

http://en.wikipedia.org/wiki/Pulse-width_modulation#Time_proportioning

So, possibly in theory, to fully engage that solenoid, you would bypass that pulse control signal and just apply a signal that was either connected to supply or ground, depending on the sense of the control signal.

However, in practice, there may be complications which need to be investigated. For a start, the solenoid may not be designed to take current 100% of the time. i.e. the PWM may never actually reach the "fully on" state, to fully engage the clutch. To avoid damaging anything, the waveform would really need to be monitored with an oscilloscope before any mods were made.

You also have to remember it is part of of a bigger system comprising of things like the ABS/VSC, steering ECU, yaw rate sensor, all sharing information over a CAN bus. Subtle control of that solenoid may be going on (even with the "lock switch" activated), which would be lost, by permanently locking it up.

Personally I wouldn't mess with it. I'd certainly want to monitor what was going on with the control waveform before attempting anything like the above.

I suspect most of the time it is doing a better job than your average driver would do with it "locked". VivianM I accept you may do better because of your "racing" pedigree. Your car makers or component suppliers test driver might out perform anything the electronic system could do, but I suspect I wouldn't.

Going off at a tangent, the pre 2009 4.3s did fall down in the fact that getting away on a slippy up hill slope could be difficult, due to the traction control kicking in, but that has been addressed with a disable switch.

Clear as mud?

[anchorman]

Thats ma boy

Don't forget Guy that you have to try to build in as much protection as you can as it is inevitable that somebody would leave it switched on when on a good road surface. That would cause undue strain on the transmission and also cause the vehicle to become unstable as the front and rear diffs fight with each other. The only exception would be Bothy's straight line sprints.

[bothwell_buyer]

haha ancs - you beat me to it! However in this weather with our roads being wet and fairly slippy, we're running number 2 with diff lock on constantly. I said to my son to be careful going round corners and roundabouts and switch it off if the roads are not slippy.. not much chance of that just now with snow still falling.

At the end of the 1/4 mile dash, I still have the diff lock on when doing a U turn to get off the race track and haven't had any problems, other than the steering being stiff due to the tyres scrubbing. The transmission is certainly well-over-engineered. I suppose it would have to be to cope with shoving an oil-burning lump and 5 doors ! :lol: :lol: