Thread: When to lock CDL

Originally Posted by trout1105

What a Good video, Even the lesser cranially empowered should be able to understand why Locking the CDL is important after watching this

Oh my giddy aunt! All the skid pan stuff in that video was comparing 2wd to 4wd in a vehicle with no centre diff at all!

The first bit showing a vehicle with a centre diff (the Defender) not going anywhere when one wheel is lifted has absolutely zero to do with what went on later in the video with a vehicle in 2wd and no centre diff.

A vehicle with a centre diff, unlocked, would have blitzed that skid pan course! Likely better than had it been locked! But that WASN’T what was being demonstrated in that video

True 4wd drive spilts power 50/50 between the front and rear axle. It is impossible to have 50/50 power split between axles with a open centre diff.
A defender with a unlocked centre diff will always send power to the one wheel with the least resistance on which ever axle that may be (front or rear). When the power is split evenly between the axles (front and rear) then true 4wd is engaged and the wheel with least resistance will drive on each axle. This allows one to drive through fast corners with more controll and stability.

The video clearly shows that....

Originally Posted by tact

Oh my giddy aunt! All the skid pan stuff in that video was comparing 2wd to 4wd in a vehicle with no centre diff at all!

The first bit showing a vehicle with a centre diff (the Defender) not going anywhere when one wheel is lifted has absolutely zero to do with what went on later in the video with a vehicle in 2wd and no centre diff.

A vehicle with a centre diff, unlocked, would have blitzed that skid pan course! Likely better had it been locked! But that WASN’T what was being demonstrated in that video

A vehicle with a centre diff, unlocked, would have blitzed that skid pan course!

What a load of old cobblers.
With the centre diff unlocked an all wheel drive is NOT a 4WD and will react on that skid pan exactly the same as a standard 4WD running in 2WD mode.
Obviously you haven't got a basic understanding of how the CDL works on a Landrover yet, I suggest that you Watch that video again

Originally Posted by 1nando

With centre diff unlocked power only ever goes to either the front or rear axle not both at the same time.

Gotta stop you right there. That is flat out wrong. The whole point of having a centre diff is to drive all 4 wheels, even on tarmac, avoiding transmission wind up.

Are you so confused you are missing the difference between “full time 4wd” and “part time 4wd” systems??

No point touching on the rest of your comments til you get that part right in your head.

Utterly basic stuff here:
Part time 4wd: only one axle (front or rear) is driven, effectively 2wd, until the transfer box control is used to select 4wd. Most basic models have no centre diff - thus two modes:
- 2wd, for use on hard surfaces
- 4wd, for use ONLY when off tarmac

Full time 4wd: has a centre diff. Drives all 4 wheels whether the centre diff is locked or not. Two basic modes:
- 4wd, CDL UNLOCKED - for use on hard surfaces. Allows full 4 wheel differentiation so no transmission windup. Comes to grief if and only if a wheel is in the air and can free spin. At ALL other times when 4 wheels are on the ground, ALL 4 wheels are driven.
- 4wd, CDL LOCKED - for use ONLY when off tarmac.

Wow, this thread is hilarious. Some people need to take a deep breath and step back a bit, maybe go for a drive on a muddy track somewhere far away from their internet connection.

Originally Posted by tact

Gotta stop you right there. That is flat out wrong. The whole point of having a centre diff is to drive all 4 wheels, even on tarmac, avoiding transmission wind up.

Are you so confused you are missing the difference between “full time 4wd” and “part time 4wd” systems??

No point touching on the rest of your comments til you get that part right in your head.

Utterly basic stuff here:
Part time 4wd: only one axle (front or rear) is driven, effectively 2wd, until the transfer box control is used to select 4wd. Most basic models have no centre diff - thus two modes:
- 2wd, for use on hard surfaces
- 4wd, for use ONLY when off tarmac

Full time 4wd: has a centre diff. Drives all 4 wheels whether the centre diff is locked or not. Two basic modes:
- 4wd, CDL UNLOCKED - for use on hard surfaces. Allows full 4 wheel differentiation so no transmission windup. Comes to grief if and only if a wheel is in the air and can free spin. At ALL other times when 4 wheels are on the ground, ALL 4 wheels are driven.
- 4wd, CDL LOCKED - for use ONLY when off tarmac.

Tact; i suggest you place your vehcile in a situation where one wheel is up of the ground. Leave centre diff unlocked and release the clutch slowly in 1st and tell me what happens. The opposite axle will not have power transfered to it unless the TC cuts in and even then its assuming that axle has the wheel with least resistance.

Again; a defender is not a Subaru AWD vehicle where the transmission and computer are able to send power to whatever wheel on which ever axlel has traction automatically.

Are they allowed to lock thier centre diffs in the mud??

Originally Posted by bee utey

Wow, this thread is hilarious. Some people need to take a deep breath and step back a bit, maybe go for a drive on a muddy track somewhere far away from their internet connection.

Originally Posted by 1nando

Tact; i suggest you place your vehcile in a situation where one wheel is up of the ground. Leave centre diff unlocked and release the clutch slowly in 1st and tell me what happens. The opposite axle will not have power transfered to it unless the TC cuts in and even then its assuming that axle has the wheel with least resistance.

Again; a defender is not a Subaru AWD vehicle where the transmission and computer are able to send power to whatever wheel on which ever axlel has traction automatically.

Ok,i am no expert,just part of the audience here,talking about no traction control,Defender as an example,
We know what happens when one wheel loses traction,
But what happens when the vehicle is driving in a straight line,on bitumen,all wheels have grip,Cdl unlocked?

Through which wheel does the torque go?

At a guess i would say more than one,maybe even all four,unlike a 2wd vehicle?

That is why part time 4WD(no centre diff) is completely different from full time 4WD.