When to lock CDL

**trout1105** · 10th May 2018, 07:05 PM

The manual also advises Not to engage the CDL on the run if there is any wheel slip and to back off the accelerator if this is the case, engaging/disengaging the CDL when stationary negates any risk of damage.

**1nando** · 10th May 2018, 07:26 PM

For those that believe a vehicle in true 4wd isnt a better handling vehicle please read the following;

4WD - Technical informations

The best rally cars in the world have 3 diffs like the defender. The front is usually a open tye diff, the centre and rear diffs are torsen/atb type diffs. Now lets think about this;

If driving in true 4wd negatively effects vehicle handling why do these vehicles have torsen type diffs in the centre diff??

At high speed on a surface with less friction than that of tarmac loosing traction through a slipping wheel can lead to loss of vechile control. Its at this point the torsen centre diff locks and sends torque to both axles. As this happens the driver is now provided the abilty to control and drive the vehicle without potential loss of control.

Now; if a locked centre diff on a surface with less friction than that of tarmac on a strecth of road im not 100% familiar with is so bad to vehcile control as some have claimed to be BS, why do rally cars have torsen centre diffs???

Now some will claim; "im talking about compressed hard dirt blah blah blah". Now I've driven a few, actually a lot of dirt roads in my time which aren't my daily comute and even if they were the fact remains they're not sealed and are subject to erosion, weathering etc. Now the way i see it is that as soon as i get off the tarmac with my family onboard, all our gear and a truck weighing close to 3 ton do i care about the little extra transmission wear of having a locked centre diff? ??? FK no! My concern in vehicle control. I want to know i can throw the steering wheel to one side if needed, take evasive action and maintain vehcile control, vehicle control that a open centre diff can not offer.

Lock it or dont lock it, i dont care what you choose to do as its each individual's choice and vehcile. However to call bs on something thats true really does my head in. Defender is a true 4wd vehcile when locked, if you dont want to use it you should have bought a fiat panda!

**DefenderBrisbane** · 10th May 2018, 07:50 PM

Now I am not any sort of expert on this, but I think that locking the centre diff on unsealed surfaces is a good idea.

However, last year we took our Defender TD5 down the Strzeleki Track enroute to the Simpson desert. Because we here headed for the desert we had left our camper trailer at home and had gear on a roof rack. This was an oztent, spare wheel, tool box, spare parts, small gas bottle, two chairs and a few other little pieces so not a lot, the object being to keep the centre of gravity down.

We did notice the affect that this load had on vehicle stability. We also found it was more noticeable with the CDL engaged. I reckon it was because the additional traction made the vehicle grip ruts and other uneven bits and tend to track along them. So, we did some of the gravel road stages without the CDL engaged.

Anyone want to comment?

**1nando** · 10th May 2018, 07:58 PM

What you felt was a vehicle working with a tighter drivetrain, more traction and a **** load of weight on the roof! Someone will say transimisson "wind up". If your on a surface with less friction than that of tarmac like dirt then it is negligible; throw in cornering, ruts driven at speed and "wind up" is not an issue.

However had you hit a bad rut, corner or needed to take evasive action with the vehicle travelling at speed and with the cdl unlocked with all that weight on the roof then chances are you could have lost control and rolled the vehicle. You would be very unfortunate to lose control with the cdl locked under the same circumstances!

Ps: you should always try to load your vehcile with the lowest centre of gravity possible. The higher the centre of gravity the greater your chances are of rolling the vehicle.

Originally Posted by DefenderBrisbane

Now I am not any sort of expert on this, but I think that locking the centre diff on unsealed surfaces is a good idea.

However, last year we took our Defender TD5 down the Strzeleki Track enroute to the Simpson desert. Because we here headed for the desert we had left our camper trailer at home and had gear on a roof rack. This was an oztent, spare wheel, tool box, spare parts, small gas bottle, two chairs and a few other little pieces so not a lot, the object being to keep the centre of gravity down.

We did notice the affect that this load had on vehicle stability. We also found it was more noticeable with the CDL engaged. I reckon it was because the additional traction made the vehicle grip ruts and other uneven bits and tend to track along them. So, we did some of the gravel road stages without the CDL engaged.

Anyone want to comment?

**Zeros** · 10th May 2018, 08:30 PM

Originally Posted by DefenderBrisbane

Now I am not any sort of expert on this, but I think that locking the centre diff on unsealed surfaces is a good idea.

However, last year we took our Defender TD5 down the Strzeleki Track enroute to the Simpson desert. Because we here headed for the desert we had left our camper trailer at home and had gear on a roof rack. This was an oztent, spare wheel, tool box, spare parts, small gas bottle, two chairs and a few other little pieces so not a lot, the object being to keep the centre of gravity down.

Anyone want to comment?

Yes... far too much on your roofrack. That load is making the centre of gravity high! A gas bottle, toolbox and spare parts?? As well as spare wheel, tent, chairs and more. ...what no full jerry cans? LOL

All that steel! Not only top heavy, but potential missiles too.

Keep your fuel, tools, gas bottles low. Preferably your spare wheel too.

...and that stopped you locking your CDL on dirt!? Um...obviously somethings not right. Top heavy, swaying all over the road and reduced traction. Glad you didn’t have a blow out or hit a washout.

**tollchief** · 10th May 2018, 10:41 PM

Originally Posted by cripesamighty

I always found this video to be helpful. In the end it is your own choice, but it’s good in some situations and not others. Personally I’d love an ATB!

YouTube

thats rubbish about the centre diff blowing up if unlocked for more than 5 to 10 seconds differentiating, read the comments under the vid.
the diff lock was deleted in some markets.

**JoshV12345** · 11th May 2018, 06:05 AM

What about driving a fast dirt road, CDL locked, then coming to a cement dip/causeway, not so much the small ones but the longer ones, do you really need to unlock for that? Or even some dirt roads where they’ve put a bit of bitumen down for a short length but then changes back to dirt, especially on a really steep hill.

**weeds** · 11th May 2018, 06:10 AM

Originally Posted by JoshV12345

What about driving a fast dirt road, CDL locked, then coming to a cement dip/causeway, not so much the small ones but the longer ones, do you really need to unlock for that? Or even some dirt roads where they’ve put a bit of bitumen down for a short length but then changes back to dirt, especially on a really steep hill.

If I can see he end than I leave it locked...

**Zeros** · 11th May 2018, 06:21 AM

Originally Posted by weeds

If I can see he end than I leave it locked...

agree. A short distance in a straight line should be ok.

**jon3950** · 11th May 2018, 11:35 AM

Unfortunately the best rally cars in the world are hamstrung by the regulations. Regulations have varied over the years but currently World Rally Cars run active (electronically controlled) centre diffs and passive (mechanical, torque biasing) front and rear diffs. If they had their choice, they would run active diffs front and rear as well.

I've been following this argument with some bemusement. There's a reason we can't all agree on whether to lock the centre diff or not and that's because there's no one right answer. In some conditions a locked diff will be a compromise, as will an unlocked diff. That is why active diffs were developed, they constantly vary the amount of lock-up to suit the conditions. Those of you who have a driven a D4 on the dirt will appreciate how well they handle - the centre diff is part of this.

Dirt road conditions vary greatly, some have high levels of grip, some don't, and to say you should always have your diff locked or unlocked won't be the best answer for all conditions. Then there's the vehicle itself, wheel base, weight distribution, available power, not to mention the speed you're travelling at. Suddenly there's an awful lot of variables to contend with.

Broadly speaking, a locked centre diff will make the car feel more planted on the road and provide higher levels of grip - in a straight line. It also makes it more reluctant to turn in. Here's where comparing a Defender to a rally car is a little unfair. A rally car has better suspension and has more power available, so you can move it around on the road and unsettle it to make it turn in. Where 4wd rally cars have a big advantage over 2wd is speed out of corners, as the high levels of grip enable you to put more power to the ground, rather than speed into and through a corner.

The best suggestion I can make is to feel what your car is doing and how it is interacting with the road. There will be some circumstances where locking the diff is beneficial, others where it isn't. And there'll be plenty in a Defender where it makes stuff all difference. I've found it makes less of a difference in the Defender than it did in the D1 or D2, but I would expect it would make a bigger difference in a 90 than my 110 and even less in a 130.

Also I think this talk of destroying centre diffs is a bit of a furphy. This is a problem in snow or muddy conditions, or off-road where traction can be completely lost on one wheel, causing significant differential rotational speeds between front and rear. I'm not convinced this would happen on your average dirt road drive.

Cheers,
Jon

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