Thread: CDL in D2

The 03 04's use Both....

It does not matter if the TC brakes 1 wheel as the other can still turn through the Diff even if the diff lock is engaged.

Disabling the TC once you have fitted the CDL is a backwards step tbh. dont know why they told you this info.

I have used both the TC and CDL in mine (2001) and as yet no problems at all, infact now I have the CDL, the TC hardly ever comes on anyway.

I always thought it would be an advantage to have both. But their rationale seemed to gel. Then I started thinking about the '03/'04 models. I guess that it would be an advantage not to have TC when driving in sand/snow though.

many thanks

Don't worry about the TC, with your CDL engaged the TC will aid you even more when and if it actually activates, there is a big differance in traction with the CDL engaged. It will reduce the amount of work your brakes will be doing too which is a good thing. If you dont disable your CDL before turning your disco off though when you restart you will have the "three amigo's " lit up on your dash (hill decent, ABS and TC). To clear this just disable your CDL with the engine running, then switch off and then restart, this wont clear the tree amigo's if you have a abs problem though

You can eliminate this problem totally by cutting the wire from the diff lock switch that goes to the SLABS ecu, that way it does not matter when you engage the CDL. This is how the 03 / 04 's are, I can start / stop, disengage / engage etc any time, and the 3 amigos never come on.

It is an interesting area..when i first got my D2 02 before CDL my dealer whose manager was a great bloke (and a mechanic who worked on early Discos and Countys) told me (before I went and proved him right) that on Straddie in deep sand the traction controlled D2 did very well and that against the Defender Extremes of the same year that had ETC and CDL locked there wasnt much in it with the Discos just needing another 500-1000 revs to get through some deep deep stuff - he put the Defeers ahead a bit because of the better beach tyres.

I asked him whether I could install CDL and it would all still work - and work like the Defenders. He told me that a bloke in Melbourne had done that and wrecked his gearbox and had then sought warranty against LR. LR refused and it allegedly got to litigation and apparently this fellow went away.

The manager put it down to this - the fact that the ETC was trying to brake wheels and it was possible that it would brake in such a way that the drive wasnt properly distributed and it put strain back on the box. I said well whats the go with the Extreme and he said that LR had told them that the software program for the D2 with no CDL was much more aggressive than the Defender and that CDL in the D2 was certainly not compatible.

I know that quite a few people have installed CDL into their D2, but I have never quite resolved all this in my mind. I suppose that if 2 wheels on the same axle braked simultaneously with CDL engaged that could cause a problem.

I know from doing quite a bit of offroading in mine from hard state forests to deep sand towing a large dual axle van in deep sand that the traction control is a pretty amazing thing, and with bigger tyres it just gets better.

Cheers

I added CDL to mine as one of the first modifications (Bar, barrier and CDL). That was done in 2001 and the only comment that I can make about it, are that it has made offroad performance better than what it was, and it would be my first offroading modification. There were stories around at the time of "cascade failures" that would happen and the world would stop spinning on its axis, those in the know said that it couldn't be done and you would have to disable the ETC etc etc etc.

In reality, it is a standard modification to 99-01 D2's and they work very very well. There are a lot of people that run ETC and CDL locked.

I would make the modification and never look back. You also cant get the situation where it tries to apply ETC to an axle group and not the other with the CDL locked. Likewise, if you use lockers and CDL and ETC, then it still only gets better and it works. Fully locked also has very very little impact on the ETC apart from when the axles are flexing a lot, though there is not a problem.

Heres a "few" scenarios REF Diff locks and ETC, you will see that the Defender ETC works a little different to the D2. The FACTS below

With respect to the mechanical effect of adding traction diffs with or without CDL, it breaks down like this:

Without CDL:
No traction diffs: 1 wheel must turn
1 Traction diff: 1 wheel must turn
2 Traction diffs: 2 wheels must turn (both on same axle)

With CDL:
No traction diffs: 2 wheels must turn (one on each axle)
1 Traction diff: 3 wheels must turn
2 Traction diffs: 4 wheels must turn

This will tell you that fitting a single traction diff is a total waste of time if you can't lock the CDL. Fitting 2 traction diffs offers no more traction and is in practice inferior to just adding CDL (CDL ensure drive to both axles and is approx 1/5th the cost). This is why most people agree that the single most effect traction modification is to add CDL.

Given that you have a traction diff installed it is 200% more effective if CDL is engaged. With 2 traction diffs installed they are 100% more effective if CDL is engaged.

It is for this reason that I chose to install CDL first then fit an ARB locker to the rear. This guarantees 3 wheels must turn with ETC assisting on the front axle. This provide awesome traction and no bad handling traits whatsoever.

What happens if you add ETC into the equation?

ETC for all its mysteries simply applies the brakes to a wheel that the ABS sensors detect is spinning faster than the others. The more mechanical diff locks you have, the less ETC will have to do, as more of the wheels are mechanically forced to turn at the same speed.

There are 8 possible diff combinations for the DII:

Standard - Front Diff Open, Rear Diff Open, Centre diff Open:
Mechanical Result: all four wheels may spin at different speeds.
ETC solution: compare speed of each wheel to that of the average of all four and apply brake to up to three wheels at any one time if their speed is greater than the average.
(Note: This is how the standard DII ETC program works. It needs to compare each wheel's speed to that of the average of all four. As designed, the DII's ETC needs to be able to apply the brake to up to three wheels simultaneously. This gives it the ability to send power not only across each axle, but also from front to rear. This is why it is said to function diagonally.)

Front & Rear Diffs Open, Centre diff locked:
Mechanical Result: Wheels on each axle may spin at different speeds but average speed of wheels on front & rear axles is the same.
ETC solution:-compare speed of wheels across each axle, apply brake to up 2 wheels, one front and one rear at any one time if their speed is greater than opposite wheel on same axle.
(This is the standard ETC program for the Defender Extreme. Its program needs only ever to compare the speed of each wheel to its opposite number. It only ever needs to send power across each axle. This is why the Defender Extreme ETC is said to work across the axle.)
(Note D11's ETC will compare each wheel to average and will only ever find one wheel on each axle that is spinning faster than the average, therefore will operate correctly.)

Front diff Open, Rear Diff Locked, Centre diff locked:
Mechanical Result: Wheels on front axle may spin at different speeds. Average speed of wheels on front & rear axles is the same. Speed of both rear wheels is the same.
ETC solution: compare speed of wheels across front axle, apply brake to which ever front wheel is spinning fastest.
(Note: DII's ETC will compare each wheel to average and will only ever find one front wheel spinning faster than average, therefore will operate correctly)

Front diff Locked, Rear Diff Open, Centre diff locked:
Mechanical Result: Wheels on front axle must spin at same speed. Average speed of wheels on front & rear axles is the same. Rear Wheels may spin at different speeds.
ETC solution: compare speed of wheels across rear axle, apply brake to which ever rear wheel is spinning fastest.
(Note: DII's ETC will compare each wheel to average and will only ever find one rear wheel spinning faster than average, therefore will operate correctly)

Front diff Locked, Rear Diff Locked, Centre diff open:
Mechanical Result: Wheels on front axle must spin at same speed. Front & rear axle may spin at different speeds. Rear Wheels must spin at same speeds.
ETC solution: compare speed of front and rear axles, apply brake to both front Or both rear wheels to slow which ever axle is spinning the fastest.
(Note: DII's ETC will compare each wheel to average and will only ever find that both front or both rears are simultaneously spinning faster than average, therefore will operate correctly)

Front Locked, Rear Diff Locked, Centre diff Locked:
Mechanical Result: All wheels must spin at same speed.
ETC solution:-None required, no matter which way it compares it can't find any difference in wheel speeds so does nothing.
(Note: DII's ETC will compare each wheel to average and will never find any wheel spinning faster than the average, therefore will operate correctly)

** Front open, Rear Diff Locked, Centre diff open:
Mechanical Result: Wheels on front axle can spin at different speeds. Front & rear axle may spin at different speeds. Rear Wheels must spin at same speeds.
ETC solution: compare speed of each front wheels and rear axle, apply brake to up to three wheels, i.e. both rear and one front, or both front or one front.
(Note: DII's ETC will compare each wheel to average and will find that one or both fronts are spinning faster than the average, both rears are simultaneously spinning faster than average, or both rears & one front are spinning faster than average, therefore will operate correctly)

** Front locked, Rear Diff Open, Centre diff open:
Mechanical Result: Wheels on front must spin at same speeds. Front & rear axle may spin at different speeds. Rear wheels can spin at different speeds.
ETC solution: compare speed of front axle to each rear wheel, apply brake to upto three wheels, ie both front and one rear, or both rear, or one rear.
(Note: DII's ETC will compare each wheel to average and will find that one or both rears are spinning faster than the average, both fronts are simultaneously spinning faster than average, or both fronts & one rear are spinning faster than average, therefore will operate correctly)

** This is why ARB advise that there is little point installing a locker without CDL as it still require brakes to be applied to up to three wheels, as does the standard DII.

So basically :-----------

What this all means is that the DII ETC programing simply becomes more redundant as mechanical locks are installed. But no combination of lockers can ever cause it to incorrectely detect which offending wheel needs braking. It just that more simple programing could have done the same job.

The only shortfall with the simpler program of the Defender Extreme is when the Extreme doesn't have its CDL engaged it cannot force power fore and aft, so can only ever force power to the wheel with the second least amount of traction. The DII can always force it to the one with the most traction.

Once CDL is engaged, both systems will work in effectively the same way.

(Note: Throughout, "Traction diff" refers to either a front or rear aftermarket diff lock or limited slip diff, e.g. ARB Air Locker/Detroit Tru- Trac)

Thanks UP - its ok to hear people say its ok, but its better to see/understand that its ok - ie that its ok to have etc and cdl.

Thanks very much for the time you have put into this.

Cheers