Thread: disco diff lock

Hi Barney,

I'll try to explain this from what I know.

When the Disco II was released in late 1999, LR kept the same transfer case that they used on the outgoing Disco I model, i.e. it had a little "nut" on the transfer case which, when twisted to a certain position, engages the internal mechanical links to engage the CDL. But this nut was not attached to anything, so the driver can't engage the CDL. You had to go underneath the vehicle, and use a 10mm open ended spanner to actuate the CDL.

I believe I might have been the very first person in Australia to say, stuff the warranty, I want CDL. So I fitted a Disco I transfer shifter onto my Disco II. The Disco I shifter actuates that nut to engage the CDL.

For a picture of this "nut", have a look here:

http://www.expeditionexchange.com/cdl

All is well and good coz it meant that the Disco II can be fitted out with any suitable mechanism to engage the CDL nut.

Then in a fit of stupidity, Land Rover decided that they wanted to STOP people from fitting CDL engaging mechanisms, so they redesigned the transfer case by *removing* that nut. This was on the late '01 to '02 model Disco IIs. So it wasn't possible at all to fit a linkage to engage the nut coz it wasn't there anymore. Where that nut was supposed to be, the transfer case casting just had a blank. Not even a removable plate. Nothing.

What this means is that the '01 to '02 Disco IIs are totally enuched.

Then when LR realised the issues with loss of CDL were real and could not be solved by the ETC system, they reinstated the original transfer case and built a new lever which could engage the nut.

This happened on the '03 model year DIIs for Australia. In the USA, they still fitted the enuched transfer case. The Yanks didn't get the right transfer case till around '04. Someone may want to correct me on this last bit.

So that is why Simon Lun and Craig Butler were able to engage their centre diff locks - coz they had the right model year Disco II that had the nut.

Hope this makes sense.

Lawrance Lee

I can confirm that the '03 Disco has a CDL lever inside the cabin, so obviously they've seen the error of their ways with the early series II.

However, can someone explain to me the benefit (if any) of fitting aftermarket front and rear diff locks in addition to the CDL?

thanks,
Chantry's

on a full time 4x4, drive is differentiated front and rear to stop windup, the CDL locks power 50/50 front/rear, as a part time 4x4 is when 4x4 is engaged (like my series 3).

Diff locks lock the diff in the axle that would normally let the outside wheel travel further than the inside wheel in corners without windup. So if you lock it both wheels travel at the same speed all the time. So corners are nigh on impossible, but if you lift a wheel, both will continue to turn. If an unlocked diff lifts a wheel, then you get no drive from wither wheel. Although the modern traction controll aleviates this problem to some extent.

so does adding separate and individual front & rear locks (such as ARB Air lockers) add any advantage over the standard CDL?

Thanks,
Marcus

YES.
it allows all wheels to have equal driving force at all times.

ETC works but is a PIA. Difflocks work far better in IMHO.

MIchael.

so CDL ensure a constant 50/50 split to front and rear but doesn't give equal drive to all 4 wheels.

So if you lift say the front left wheel, you are relying on traction control to transfer drive to the front right wheel, whilst the back ones will continue going as normal??

Thanks,
Marcus

that is right, a diff lock is a mechanical device that ensures bothe weels have equal power.

CDL is front to rear, Diff lock is left to right 50/50 if that helps make sense of it.

One important thing that the Centre Diff Lock does is that it not only distributes the drive equally to the front and rear axles, but *very importantly* it delivers the BRAKING evenly between the front and rear axles.

Now in all vehicles, the front wheels have the bigger, more powerful brakes. And the rears are typically less powerful.

Consider the following situation - you are trying your hardest to crawl up a steep slippery hill but halfway up, your tyres collectively are losing to much traction to keep going. So you stop, with your foot hard on the brakes, the intent being to ease off backwards down that hill to have another go.

Now remembering that the front wheels have the majority of the braking power proportioned to it, and they are now significantly LIGHTER than the rear wheels which have the bulk of the weight of the vehicle on it.

If you do NOT have a CDL engaged, what this means is that when you ease off your brakes a little to allow the vehicle to begin backing up under its own weight from that steep slope, the front wheels remain fully locked and the rear brakes are now tasked with the job of controlling the speed of your descent. This is bad because the front wheels being still full locked, and with little grip or weight on them, means that you've lost any steering ability........ this is BAD! 8O

With the CDL engaged, the front wheels are not allowed to remain locked while the rear wheels are turning. In effect, the braking from the front wheels is transfered thru the engaged CDL to the rear wheels, so in effect, both axles are controlling the descent, not just the rear axle.

So the CDL is very very important for backing down a steep/slippery hill.

Food for thought.

Cheers,

Lawrance