Diff Lock vs Traction Control

[OnPatrol]

But I really think the rear locker on the Paj is a waste of time. The problem is that the traction control is turned off when the locker is turned on so after some testing in a few different scenarios I found the traction control got me a lot lot further than the rear locker did.

I am not sure why the TC had to be turned off??? If you have a 4WD and add an ARB rear locker then the TC stays on.

Now if you added a front locker as well then that would be a different story!

Firstly there are three differentials in a Paj (Front, Centre, Rear).

In 2wd - centre diff lock is disengaged. If you loose momentum and loose traction in one rear wheel, then the car will stop.

In 4wd Hi - all wheel drive mode. The centre diff lock is disengaged. If you loose momentum and you loose traction in any of the four wheels, then the car will stop.

4WD Hi Centre Locked and 4WD Low will engage the centre-diff-lock. This locks the prop-shaft and tail-shaft, becoming one locked shaft hence giving equal drive to the front and rear differentials. If you loose momentum then the only way the car will stop is if you loose traction on one front wheel and one rear wheel.

Cross-axle diff locks. The factory locker is for the rear differential. By engaging the rear diff-lock, the left and right rear axles are locked as one unit, hence giving equal drive to the rear left & right wheels. To stop the car in this configuration, then you'd have to loose traction on both rear wheels and one front wheel.

In Mitsubishi's wisdom, I suppose they figured that once you have the rear diff lock engaged, then you really don't need traction control to operate on the front axles.

You have to be pro-active to get the most benefit from the rear diff lock; engage it before the obstacle. Make sure that it's engaged. Speed of engagement varies between diff-lock manufacturers. You'll need to back off the throttle to allow the diff lock to engage, because generally diff locks will not engage or disengage under load. If you follow this simple rule of engaging the diff lock before the obstacle and making sure that it is fully engaged, then traction control will never be as good as a diff lock.

Taction Control is a reactive system. The computer has to detect wheel spin before it engages the ABS to brake the spinning wheel. This then fools the differential to apply power to the stationary wheel.

On the other hand, if you already engaged the rear diff lock in anticipation of the obstacle, then you can drive a lot more controlled and much less wheel spin (much less track damage).

I also feel that traction control is harsh on your differential, but that's just my opinion and engineers may have a different view on that.

[danc12]

consider!

Not sure I agree with all of this.

The caveat to your statements should be that the traction control is off
"In 4wd Hi - all wheel drive mode. The centre diff lock is disengaged. If you loose momentum and you loose traction in any of the four wheels, then the car will stop." In fact on loss of traction on one rear wheel the amount of power delivered front to rear changes dynamically from 33% to 50%, to stop requires loss of traction of one wheel each in both the front and the rear. Otherwise why have 4 wheel drive at all. What the centre diff does for you is compensate for the various diameters of wheel travel on turns to prevent windup. Once centre diff is locked the car has a significant tendency to go straight and hence requires a slippery surface to allow it to work properly. Locking provides equal power front and back always and consequently no tolerance for change in turning radii between front and back. it's the most useful in going straight through heavy boggy conditions or where there is a lot of potential slip say up hills. Don't use this when driving on normal dirt roads especially with tight corners, turning radii are affected or if there is not enough slip you can stuff the gearbox.
What traction control has done is removed the need for limited slip diffs, a mechanical approach to locking the diff in case of slip on one wheel. LSD although effective is also reactive, less so than Traction control and less efficient ie reduces fuel economy. Also if used a lot off road prone to earlier failures.
Diff lockers get rid of the reaction time and obviously if the diff locker is in place then mechanically left and right wheel are a solid connection, ie left wheel can't start spinning without the right wheel spinning, and if this happened the last thing you want is for the traction control to cut in and try to stop the spinning as this would stop both wheels. Mitsu don't have the option of only having traction control on the front for say when a diff locker is used.

[Hookedon4wding]

So, it is better to use the rear locker (minus the TC on the front wheels) on steep loose hills or rely on the TC (on all 4 wheels) and not the locker?

Anyone given the factory locker a good workout yet?

[danc12]

here is a good article

http://www.pps.net.au/4wdencounter/articles/difflocks.html

The following extract:
"Diff locks obviously provide more traction but their effect is more dramatic in certain terrain types. The greatest improvement comes on deeply gouged rocky tracks where there is plenty of traction and the rough ground results in opposite wheels not touching the track. The least improvement comes in smooth slippery tracks where all wheels have roughly the same weight on them but there is simply not enough traction. It is quite common in these circumstances for all four wheels to spin even when diff locks are not fitted.

A diff lock is not some magical device that can create more traction for your vehicle, all it can do is make avaliable the same amount of torque to each wheel. In simplistic terms, a four wheel drive vehicle is only a 2WD whereas a front and rear diff locked vehicle is a true 4WD. In pratical terms, a vehicle with front and rear diff locks will go places that no ordinary 4WD can."

[OnPatrol]

Not sure I agree with all of this.

The caveat to your statements should be that the traction control is off

Good pick up and this is always a complicated subject. You?re right that in explaining differentials we have to take traction control and LSD out of the equation?otherwise it further complicates how the mechanics works.

"In 4wd Hi - all wheel drive mode. The centre diff lock is disengaged. If you loose momentum and you loose traction in any of the four wheels, then the car will stop." In fact on loss of traction on one rear wheel the amount of power delivered front to rear changes dynamically from 33% to 50%, to stop requires loss of traction of one wheel each in both the front and the rear. Otherwise why have 4 wheel drive at all.

If you consider one differential, the tendency is to apply power to the least point of resistance. If you?re in 4WD Hi ? Centre Diff Lock disengaged, means you have 3 differentials in operation. You only need one wheel spinning before the vehicle stops, based on the true characteristics of differentials.

An example would be one front wheel in the air (the Pajero salute as I call it). Drive from the Centre Differential will all go to the front driveshaft and onto the front differential; then the front differential will apply most of the power to the wheel in the air.

Another practical example is when Rugrat broke a front axle on his Pwado during our Advanced Course. One broken axle and he had no drive to all four wheels. The Pwado is full time 4WD so all the drive was going to the broken axle (least point of resistance). Luckily the front axle had a clean break and he was able to drive home by engaging the centre diff lock.

You mentioned the transfer of power from 33% to 50% front to rear. I don't think that this is a true characterics of a differential. It's a modification to the drive train by the manufacturer to offer more driveability. The softroaders tend to have this feature because they don't have a transfer case..it's like having LSD in the centre diff.

What the centre diff does for you is compensate for the various diameters of wheel travel on turns to prevent windup. Once centre diff is locked the car has a significant tendency to go straight and hence requires a slippery surface to allow it to work properly.

The centre diff actually compensates for the difference in rotation between the front driveshaft and tail-shaft. Once the centre diff is locked the front driveshaft and tailshaft are connected as one unit. Effectively the same as a part-time 4wd.

Locking provides equal power front and back always and consequently no tolerance for change in turning radii between front and back. it's the most useful in going straight through heavy boggy conditions or where there is a lot of potential slip say up hills. Don't use this when driving on normal dirt roads especially with tight corners, turning radii are affected or if there is not enough slip you can stuff the gearbox.

Not quite true. Since you have a differential between the front axles and one between the rear axles you can still turn on dirt roads. Dirt roads also allow some slip. I certainly don?t have a problem with my GU Patrol with part-time 4wd engaged on dirt roads. However, don?t ever lock the centre diff on bitumen otherwise you will get transmission wind up. It?s not just the gearbox you?ll stuff up, the front driveshaft and tail-shaft are likely to twist and your transfer case will probably seize. The weakest point in the system will break first and hopefully it?s the cheapest part (CVs or axles).

What traction control has done is removed the need for limited slip diffs, a mechanical approach to locking the diff in case of slip on one wheel. LSD although effective is also reactive, less so than Traction control and less efficient ie reduces fuel economy. Also if used a lot off road prone to earlier failures.

You can have LSD operating with traction control. It should actually complement each other. Traction control is a computer system that works via the ABS and LSD is a mechanical system inside the diff housing. Both can work together. Besides, doesn't the Gen3/Gen4 Paj retain the rear LSD even with traction control fitted.

Diff lockers get rid of the reaction time and obviously if the diff locker is in place then mechanically left and right wheel are a solid connection, ie left wheel can't start spinning without the right wheel spinning, and if this happened the last thing you want is for the traction control to cut in and try to stop the spinning as this would stop both wheels.

With the rear diff lock engaged and if both rear wheels are spinning, you will still get power to the front differential because the front driveshaft and tailshaft are connected. Then you would have to loose traction on one of the front wheels as well before the car will stop. If you lost traction on 3 wheels then you?re not going anywhere anyway.

Mitsu don't have the option of only having traction control on the front for say when a diff locker is used.

Technically you can still have traction control operating with the centre diff and rear diff locked. Traction control utilises sensors at each wheel and monitors them independently and checks the variance of wheel speed between axles. It can work independently of diff locks. On the other hand; with the centre diff and rear diff engaged then it?s unlikely that traction control will activate anyway, so that's probably why Mitsubishi has decided to disengage traction control once you switch on the rear diff lock.

[matthewfnorbert]

do we have a mech centre diff or a viscous type?, and if viscous can it then apportion power to front and back as dictated by ecu regardless of slip therefore vehicle does not stop..?

[danc12]

well that's the last time I post!!

"You mentioned the transfer of power from 33% to 50% front to rear. I don't think that this is a true characterics of a differential. It's a modification to the drive train by the manufacturer to offer more driveability. The softroaders tend to have this feature because they don't have a transfer case..it's like having LSD in the centre diff." Pajero have this feature, I've never tried it knowingly but its in the spec sheets. Wouldn't this mean that it would require one wheel in front and one in back spinning to strand the vehicle? Perhaps Prado with their constant 4WD does not have the torque split capability of the Pajero?


"I certainly don?t have a problem with my GU Patrol with part-time 4wd engaged on dirt roads. " I have had a jackaroo shorty, prado and 3 pajeros and if you lock the centre diff on all of them they like to go straight even on dirt, turning radius is certainly affected, as you turn, if there is not enough slip, you will hear the tyres scuff and the truck won't turn as far.

"Besides, doesn't the Gen3/Gen4 Paj retain the rear LSD even with traction control fitted." Nope, no LSD.

"On the other hand; with the centre diff and rear diff engaged then it?s unlikely that traction control will activate anyway, so that's probably why Mitsubishi has decided to disengage traction control once you switch on the rear diff lock. " If both back wheels spin, with the diff locker on, it is feasible that the traction control will apply the brake to both wheels or each intermittently and this would stall the vehicle.

[6G74]

do we have a mech centre diff or a viscous type?, and if viscous can it then apportion power to front and back as dictated by ecu regardless of slip therefore vehicle does not stop..?

In the some of the manuals i have read, they refer to it as a viscous, but too look at the technical drawings, it looks just like a normal mechanical diff... what ever all that means

[1993 NJ LWB]

well that's the last time I post!!

"You mentioned the transfer of power from 33% to 50% front to rear. I don't think that this is a true characterics of a differential. It's a modification to the drive train by the manufacturer to offer more driveability. The softroaders tend to have this feature because they don't have a transfer case..it's like having LSD in the centre diff." Pajero have this feature, I've never tried it knowingly but its in the spec sheets. Wouldn't this mean that it would require one wheel in front and one in back spinning to strand the vehicle? Perhaps Prado with their constant 4WD does not have the torque split capability of the Pajero?

No loss of traction on just one wheel will cause the paj to stop. I have free wheeling hubs at the front and have tried this myself: Put it in 4wd h leave 1 front hub unlocked(simulates no traction) and the thing wont move even on flat ground.

"On the other hand; with the centre diff and rear diff engaged then it?s unlikely that traction control will activate anyway, so that's probably why Mitsubishi has decided to disengage traction control once you switch on the rear diff lock. " If both back wheels spin, with the diff locker on, it is feasible that the traction control will apply the brake to both wheels or each intermittently and this would stall the vehicle.

No if the back diff lock is in there is no way the traction control will brake any rear wheels as it senses the difference in wheel speed between left and right wheels. Thats how it knows a wheel has lost traction, when one spins faster then the other. If both wheels are spinning at the same speed then computer thinks you have good traction and nothin is wrong. If it just sensed wheels spinning fast it would be slamming on the brakes as you go down the freeway.

Cheers,
Jack

[Mike DiD]

Good pick up and this is always a complicated subject. You?re right that in explaining differentials we have to take traction control and LSD out of the equation?otherwise it further complicates how the mechanics works.

This is a discussion in the Gen4 Pajero section - the Gen4 has Traction Control ALWAYS ON (except when Locking the Rear Diff if you have it).

So discussing Diff operation without Traction Control is a purely hypothetical discussion.

If one wheel loses traction in an NS, the vehicle does still move.

[Mike DiD]

Quote:
Originally Posted by danc12
What the centre diff does for you is compensate for the various diameters of wheel travel on turns to prevent windup. Once centre diff is locked the car has a significant tendency to go straight and hence requires a slippery surface to allow it to work properly.

The centre diff actually compensates for the difference in rotation between the front driveshaft and tail-shaft. Once the centre diff is locked the front driveshaft and tailshaft are connected as one unit. Effectively the same as a part-time 4wd.

??????? Dan's statement is perfectly correct.

[Mike DiD]

However, don?t ever lock the centre diff on bitumen otherwise you will get transmission wind up. It?s not just the gearbox you?ll stuff up, the front driveshaft and tail-shaft are likely to twist and your transfer case will probably seize. The weakest point in the system will break first and hopefully it?s the cheapest part (CVs or axles).

This has happened to me occasionally with no damage to the Pajero. You can't drive very far or fast, because it feels like the handbrake is on when you turn the wheel off-centre.

[Mike DiD]

Technically you can still have traction control operating with the centre diff and rear diff locked. Traction control utilises sensors at each wheel and monitors them independently and checks the variance of wheel speed between axles. It can work independently of diff locks. On the other hand; with the centre diff and rear diff engaged then it?s unlikely that traction control will activate anyway, so that's probably why Mitsubishi has decided to disengage traction control once you switch on the rear diff lock.

Because Mitsu disabled Traction Control when the Rear Diff is locked, if you lose traction on both rear wheels and one front wheel you have no drive.

If they had decided to leave Traction Control enabled, then when one of the Front wheels lost traction, it would be braked you would still have drive to the other front wheel. Your only option is to apply gentle footbrake pressure to obatin some traction on the wheel with grip.

[psproule]

This has happened to me occasionally with no damage to the Pajero. You can't drive very far or fast, because it feels like the handbrake is on when you turn the wheel off-centre.

Um - having seen the inner workings of the transfer case and centre diff lock in these, and in particular our old one that had worn the teeth in the diff lock and used to slip frequently with a nice graunching noise, I would suggest that this is the weak point and should be treated with caution. With high traction tyres on a solid surface on a sharp curve you are applying a hell of a lot of force on the diff lock. Ours wore to the point that it would let go regularly on steep inclines or situations where the front had traction and the rear didn't (eg - rear wheels in mud). Cost me $3k to rectify.

[kevinluigi23]

What the centre diff does for you is compensate for the various diameters of wheel travel on turns to prevent windup. Once centre diff is locked the car has a significant tendency to go straight and hence requires a slippery surface to allow it to work properly. Locking provides equal power front and back always and consequently no tolerance for change in turning radii between front and back. it's the most useful in going straight through heavy boggy conditions or where there is a lot of potential slip say up hills. Don't use this when driving on normal dirt roads especially with tight corners, turning radii are affected or if there is not enough slip you can stuff the gearbox.

I tried the 4HLC for dirt driving and the handling was very stiff. I put it back to 4H and it was much better and smoother. I understand the benefits of the locked centre diff but I got to the point where I didn't see the point of 4HLC. If it was rough enough that I needed locked centre, I would also need low range.

Actually, on the windup and the steep hills, what are you supposed to do when you are going up a steep hill in 4LLC and there was a hairpin turn? I suppose you just cop the grinding as you go around the corner and cop the diff windup.