Open centre diff- I'm a convert

[Rusty62 Advanced Member Find all posts View Profile Close Rusty62]

Both my brothers 150 GXL and my 120 VX are fitted with rear lockers. Makes a very competent car with traction control working on the front and locked rear. Would always lock the centre before locking the rear.

As for fitting a traction control to 120 GXL would be a major refit. Different brake master cylinders, yaw sensors, plus wiring looms.

Rusty.

[PradoJim Member Find all posts View Profile Close PradoJim]

Jim
My brothers 150 was a 2012 GXL 5 door. Both diffs and centre where open and traction control. We did fit a airlocker to the rear for slow work.
Rusty.

Thanks Rusty. That's what I suspected re the front and rear. I don't know where Journo's get their tech specs from sometimes. The next level up in the 3 door, the VR (equivalent to a Kakadu) has a rear locker but I figured for $1500 or so, I could have one fitted. I didn't really want all the other flim flam from the top spec model.

[Fred63 Advanced Member Find all posts View Profile Close Fred63]

Do you have a link to that thread?

They are 2 of my posts but look through the entire thread

http://www.pradopoint.com/showthread...l=1#post535614
http://www.pradopoint.com/showthread...l=1#post538441

[Razorback81 Advanced Member Find all posts View Profile Close Razorback81]

As for fitting a traction control to 120 GXL would be a major refit. Different brake master cylinders, yaw sensors, plus wiring looms.

Rusty.[/QUOTE]

Thanks Rusty

was a wish full thought

[Anth120playdo Banned Find all posts View Profile Close Anth120playdo]

You should lock your centre & any other lockers when on rough tracks.

Do what you can to avoid the traction control doing the work.
You have a heap of low range torque working against your brakes, it puts pressure on the whole driveline, often in a jerky manner.
Yes the Prados & their drivelines are tough, but I have seen them strip the splines in the driveshaft to the tripod!

So yes you have the technology, but IMO try & use old fashioned driving skill to save wear n tear on the driveline.

Note: 120 traction control is very average compared to the 150's.

[Mule Member Find all posts View Profile Close Mule]

My 1999 disco 2 had traction control and open diffs all round. Worked great. Worked even better when I fitted a cable to activate the centre diff lock that was there as a left over from the D1 but left inoperable when traction control was added to the D2. The centre diff lock takes a heap of load off TC and unless the 150 prado has an extra super heavy duty ABS system (unlikely) then the TC will overheat when you work it hard and becomes less effective so I would definitely engage centre diff lock in the rough. The only thing that can happen is you may scuff a little rubber off your tyres doing rock work but if you have that much traction then obviously turn off the centre diff lock.

Not sure I can agree that traction control is the enemy of your drive line. Much worse is when a wheel is up in the air spinning free (no traction control, no diff lock) under power and then lands back down on the ground. This is the classic axle / universal/ diff crunch situation. Traction control will save your driveline! Use both if you have them when required.

[MYT150 Member Find all posts View Profile Close MYT150]

Personally as soon as I get on a dirt road I lock the center diff, that is what it is meant for and I paid for it so I might as well use it. It also means I know I will have power to at least two wheels rather than just one, even with TC. And in a hard off road track if I had a locker fitted and I felt I might need it I would engage it before hand so it was also earning it keep.
Just because you mightn't need it doesn't mean you shouldn't use it to take the strain off other parts of the drive train that might break easier.

[PradoJim Member Find all posts View Profile Close PradoJim]

I understand what you're saying re locking the centre diff. I have another 4wd and I will always engage my rear locker if I think I'll need it rather than get stuck halfway or have to use inertia when it could bounce me into a tree or rock.

The thing is, the book says pretty plainly not to use it unless you have to. And the centre diff is not an ordinary diff, it's not like you've only got power to one wheel like an AWD. That was really the gist of this thread. I'm a believer in what you guys are saying and in using everything you've got. But I decided to "play it by the book" and give Toyota's advice a go and was very surprised. And as mentioned, hardly heard the TC at all.

Having the centre locked when negotiating rocky ground with no give makes me feel very uncomfortable from my mechanical seat of the pants.

I once inadvertently left a centre diff locked in another 4bee in my garage. All I did was reverse into the driveway which has a large radius curve and halfway through the curve I knew something was wrong. I thought the brakes were sticking or hand brake was on. That's how much mechanical stress is going through the system if the centre is locked and the ground is not loose. When I think about how much manoeuvring I was doing on rocky ground last trip, I'm more than happy to leave it unlocked given that it has demonstrated (to me) that it's a special kind of diff and the car did it all with very little fuss.

A couple of years with the car and I might find that my belief is mistaken, I'll be the first to admit it

If I really want to find out how good that diff is, I need to do this with TC off. When I get the chance, I'll have a go.

[PradoJim Member Find all posts View Profile Close PradoJim]

They are 2 of my posts but look through the entire thread

http://www.pradopoint.com/showthread...l=1#post535614
http://www.pradopoint.com/showthread...l=1#post538441

I read these as well, before my first outings. Gave me the impetus to try it unlocked.

[Rusty62 Advanced Member Find all posts View Profile Close Rusty62]

To relieve stress from the transfer case leave the center unlocked. On turns the radius difference between front and rear axles loads the transfer until one wheel slips, usually a rear inside and putting a lot of pressure on your CV on full lock. Try this next time you are on loose gravel and do a U turn. Center unlocked no issue, center locked and inside rear will slip. Also your turning circle will increase. Obviously lock the center anytime you are climbing, water crossings etc. If you have a rear locker (as stated above) lock before you need it.
The majority of offroad we do in unlocked until just before we need it. On the Laura / Maytown track having the center unlocked made the car very maneuverable and as we had trailer in tow a lot of full lock was needed.
I disagree with some who say to lock the rear diff on descending and some rocky terrain. With the rear locked it tends to slip sideways as the loaded wheel skids on rocks but when unlocked the rear stays straighter. Again lock just before needed.

This really became noticeable when we had our 60 and 80 series. Both with twin lockers. When crossing a dry rocky river bed and both diffs locked the car was constantly falling off rocks and bumping sideways. When unlocked the car stayed relativity straight with a small grovel of wheel slip. A lot more comfortable and controlled. Wish we still had the 80, twin lockers, 270 lt tanks, stratos seats, bars and 12000 winch. 285/75/16 BFG muds, good suspension.

Rusty.

[Symo Advanced Member Find all posts View Profile Close Symo]

I tested the centre lock and concluded about 6 months ago that the car is more competent with it unlocked.

The reason being is the Torsen design is LSD by nature, this is due to the entire assemble rotating as 1:1 unit when torque is applied from the engine side. The system can split the torque only when sufficient friction from the wheel end is present, such as on a high grip surface. This phenomenon occurs due to the worm wheel (driven by the engine) can't turn the worm gear (resistance from the road).

The worm gear is cut close to perpendicular to the teeth on the worm wheel, thus the worm wheel binds against and the whole unit turns 1:1, when the road surface forces exceed the friction from the worm gear pushing (rotation against) the worm wheel it starts a differential rotation limited by that friction, the friction between the worm gear and worm wheel is controlled by the angle of the helical teeth, and is thus set in manufacturing.

This affect is easily felt in wet polished concrete, roll at full lock slowly and all wheels turn differential and no wheel slips, apply engine torque and this force is greater than the friction on the wet concrete and suddenly all 4 wheels start turning at the same speed and the car should under steer and push wide. The same thing as if the centre diff is locked.

This is why driving on gravel roads with a locked centre is dumb because you are inviting under steer and loss of control to occur, the LSD Torsen will put perform the lock providing the right combination of grip. This is why Audi hosed the completion in the 70s and 80s with their Quattro Torsen 4WD.

The dick lock does about 5-10% improvement only and will take some load off the TC on extreme worm hole climbs, but you'd still be able to climb it with the LSD unlocked.

Mud and sand often benefits from locked centre and TC off.


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[r4ndll Avid PP Poster! Find all posts View Profile Close r4ndll]

All well and good but us peasants in 120's with no TC can't engage Low Range without engaging centre diff lock.

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

So this thread is about driving on rocky or hard terrain. I can't see any benefit in not locking the centre diff on sand?

[drew_1 Find all posts View Profile Close drew_1]

I assume the preference for not locking the centre diff is on rocky tracks and not on sand?

that's contrary to my experience, krypto. I've never engaged the centre diff on Fraser, Straddie, Stockton and east to west on the French Line with (mostly) no real probs that adjusting tyre pressures didn't sort. On steep scrabbling tracks or mud it's always locked

[Mule Member Find all posts View Profile Close Mule]

The aim is to have tyre placement so that there is even traction and forward motion, the better the driver, the better the suspension articulates the more likely you will not need traction control or diff locks.

TC is perfect for firm rock where there is good traction but you get wheel lift over undulations.

On flat sand you get very even traction to all 4 wheel so locking or even TC is of little help. Contrary to some opinions I have not found traction control to cause problems on flat sand, it is just that you don't need it.

On climbing steep dunes the weight is on the rear so the rear has good traction but not so good up front and you may then get a front wheel spinning if the centre diff is not locked or you don't have TC.

Yes, locking diffs when on a firm surface will wind up the drive train and could do damage. That said my wife called me once to say the car was behaving badly, turns out she had accidentally engaged the front and back air lockers and had driven on the black top for 10km and around town. Fortunately no damage done but I told her to park it immediately and drove over to rescue my pride and joy!

If I have been climbing a steep rutted and loose surface track with the diff locks engaged and come across a rocky section in the track it will want to understeer and shudder as you force the car around the corners so it is time to flick off the diff locks but again no damage other than a little rubber scuffing.

It would be fair to say that you will not damage your prado if you engage the centre diff lock when going off road. It is just that you don't always need to engage it and sometimes it makes it a little cornering harder.