Thread: When to lock CDL

My 2 cents worth.
I did a trip out west past ceduna surfing fishing last year.
Did lots of beach driving chasing mulloway, sometimes 30km up the beach or more and then back over a couple of weeks.
I rarely locked the cdl (in my ignorance ???) to prove to my mate in his 80 series toyota how good defenders are on the beach.
On the 20 hour drive home to melbourne i noticed how much louder and whining my transfer case was.
Coincidence ??
Now I always lock the cdl with my new transfer case.

Originally Posted by tact

Glad you now know that was unwise... (not bothering to lock your CDL when you had one with an ATB in it).

You're welcome! Given through my efforts and persistence against all odds and insults - you now are well aware that: if you were tootling along a dirt road and struck some slippery bit that could easily be so slippery that your ATB would have also behaved like it was an open diff .... and sent you up that tree you worry about me hitting. (Where is that tree? Chainsaw is ready to go!)

Looking on the bright side... you survived all those long drives with your ATB unlocked, perilous as you believe that (a diff that behaves as if open when things have turned to custard) may be!




Still persisting with the "full time 4x4 isn't true 4x4 with CDL open. Lock the CDL and there it is - true 4x4"

You haven't given one of my suggestions a try have you. The one about jacking up a wheel on the front axle, and one on the back as well, lock your CDL.... and try to drive your "true 4x4". How true is it?

No hard feelings re your comments about losing respect for me. I still care enough about you to write:
"Y'all remember now, lock your centre diff even if its got an ATB centre - just cannot trust them when a wheel loses all traction!"

https://youtu.be/gwm_-SA8jlQ

YouTube

Once more. The first minute clearly says it all

Originally Posted by 1nando

Who mentioned locking the front and rear, is that what you mean by your last statement or are you implying locking the centre diff distributes torque 50/50 front and rear?
......

Who made the claim that locking a diff doesn't give you 50:50 torque across it?
I'm thinking you're confused as to what some replies were describing!
I was the one with the RRC tow starting the 8ton truck on gravel driveway where I did get 50:50(ish) drive front:rear when I had 1 front(LHS) and 1 rear(RHS) spinning for a short time before they gripped and the RRC with all open diffs started to pull the 8ton truck.

Originally Posted by ProjectDirector

Phew , I am the OP.
....
I thought the same applied for defender but given the transmission windup possibility made me ask the question anyway.
.....

It shouldn't produce transmission windup.
But as mentioned by others, and as I've experienced with my part time 4WDs, you can experience more understeer in some situations.
TBH, I now lock the CDL on fast dirt in my D1(where I never did in my RRC) but don't really feel any excessive understeer(like my part time 4WDs gave the feeling of).

Originally Posted by 1nando

https://youtu.be/gwm_-SA8jlQ

YouTube

Once more. The first minute clearly says it all

In summary the first minute says engage 4wd as soon as you leave the tarmac for safety as 4wd is safer than 2wd on dirt roads.

Agree wholeheartedly that all part time 4wd owners such as yourself should get out of the vehicle if necessary to lock hubs, and shift that lever or dial from 2Hi to 4Hi. Much safer than 2wd. Do it.

Owners of full time 4wd vehicles are in 4wd on road and off-road already. No need, not even a means to, shift out of 2wd. (By all means lock that centre diff though whenever there is a chance of wheelspin - or earlier if you so desire.)

Where there is any contention at all is that you have embarked on a rather ill informed mission that preaches incorrectly that:
- an all wheel drive with centre diff open isn’t a “true 4wd” because one wheel spinning means no drive
- with centre diff open only the front or rear wheels can be driven(!?? So wrong!)
- gotta lock that CDL to then be in “true 4wd”
- (which of course sets up the driveline just like a part time 4x4 in 4Hi or 4Lo - I.e. front and rear drive shafts are locked together)
- locked CDL is “true 4wd”, unlocked isn’t, despite the fact that crossaxled (ie two wheel spinning wheels) will see your “true 4wd” with no drive either. Why aren’t the other two wheels driving?
(All debate to date setting aside assists like TC etc)

Along the way scrambling to support the unsupportable (above) you have revealed a deep misunderstanding of ATBs. Misplaced trust for sure- Demonstrated by your “not bothering to lock CDL with an ATB fitted”. Not realising that on open dirt roads the confidence an ATB gives when things are within the ATBs constraints - can lead to disaster when a wheel, any wheel, does wheelspin and the ATB suddenly behaves like an open diff... and you are driving faster than you might have been otherwise.

The “true 4wd” assertions you make regarding vehicles with front and rear driveshafts locked are unsupportable. It takes technology like ABS/TC or diff locks in front & rear axles to make a vehicle you label as “true 4wd” actually come close to being able to drive all 4 wheels all the time.

In practice, on that fast dirt road, your “true 4wd” (without other tech) will be able to slip, or spin up, a front and/or a rear wheel.

There sure are times when having the CDL locked, on fast dirt roads, is a must. Eg I have have driven very loose scree dirt roads where the stones are like ball bearings. With CDL open any sudden movement of the throttle, anything less than intensely delicate throttle handling, would see revs rise out of proportion to forward travel (wheel spin starting). So I lock the CDL. (The “any chance of wheelspin” postulation).

As others suggest sometimes it’s good to lock the CDL just for the sake of it, using the mechanism to keep it functional etc. I do that too.

Something appropriate
insanity.jpeg

I would like to add my 10c worth.

I have a 2002 D2 which I fitted with a CDL and previously owned 2x RRC with LT95 and one RRC with Borg Warner (BW.)

It is a lot easier to start on dry sand with the CDL engaged than with a BW as the BW acts as an open diff until it gets "over the hump". I always found that the first 10 metres were a struggle.

I used the D2 on sand before CDL on a sand training day at Stockton and had enormous TC intervention particularly on long slopes. Once I had the CDL , I have never really tried to start on dry sand without it . I went up to Rainbow beach last year and was amazed how easily the D2 started on dry sand at the Northern exit to the corduroy track.

I don't use CDL on wet sand at low tide until I need it to cross dry sand on the beach exits. I have never had TC come on on wet sand at Rainbow. Stockton is a different matter. I don't go near the wet sand there as it is treacherous.

I agree that the CDL is desirable on loose straight dirt roads. However I did the GRR towing my 1000KG camper before I fitted the CDL and when I dismantled the LT230 , the diff shims were in excellent condition at about 180KK. So Ashcroft may be talking Britain where everything is muddy and slippery.
Last week I visited Yarrangobilly caves where the exit and entry tracks are firm but corrugated dirt with many hairpins. I didn't lock the CDL and traction control only activated once on the corrugated exit of a hairpin.
I consider that the stresses from drivetrain windup when traversing very twisty firm tracks are IMHO more than the stresses induced by any wheelspin so I don't lock the CDL in these circumstances. If you have grippy tyres the windup is pretty extreme .

Finally I also think that lubrication plays a role in centre diff failure. To get my CDL nose I bought a dismantled LT230 with CDL with AFAIR a reported 240KK on it. It had reportedly not been off road. However the diff shims were gone just about completely and there was a tonne of swarf in the little sump below the Diff.

You must avoid wheelspin at all costs. There used to be a bloke in a club I was in who used to go through axle diffs all the time. While he probably had his CDL locked in his D1 he used to sit at obstacles spinning wheels and the axle diff shims used to grab and seize.

Regards Philip A

Glad I survived all that dirt road driving I did BEFORE I got a 4wd! Mini Mokes, Vanguards and various MOWOG products, not one of which was 4wd, or had a CDL! Learnt very early on to read the conditions and drive accordingly. Just like I still do!

Originally Posted by donh54

Glad I survived all that dirt road driving I did BEFORE I got a 4wd! Mini Mokes, Vanguards and various MOWOG products, not one of which was 4wd, or had a CDL! Learnt very early on to read the conditions and drive accordingly. Just like I still do!

Lucky to be alive!

(At least you were under no illusions that your moke was a "true" front wheel drive and therefore inherently safer than it truly was...)