Thread: Centre diff lock??

Originally Posted by Aaron

I put the CDL in when im scared like a little baby.

Its the "please help me god" gear.

In actual fact, Ive NFI idea what it does... just makes it harder to steer.

i know it locks the centre diff, and I know people say its not the same as diff locks. people still fit diff locks to cars with a CDL.

so what does it do?

Lets see i I can explain.

CDL locks both front and rear prop shaft together. Which means power from engine is shared 50/50 to front and rear axle.

An axle/diff locker, locks the two half shafts together which means that each wheel is getting 25% of power from engine.

With CDL and diff lockers engaged get two wheels off the ground then you still have 50% of power going to two wheels on ground. IF that 50% power is enough to maintain forward motion (assuming ground is strong enough) you go forward.


OK no CDL or diff lockers engaged.

Think of power like water. It will take the route of least resistance. i.e. I you have a wheel off the ground it is easier for power to turn a free spinning wheel then to turn a wheel on the ground. Hence your 4 x4 is going no where as 100% of power is going to a free spinning wheel.

Engage CDL then 50% of power goes to free spinning wheel and 50% to other axle. With luck you have 2 wheel drive and forward motion.

Engage axle/diff locker on axle with lifted wheel as well as CDL your free spinning wheel gets 25% of power and you have 3 wheel drive

Hope that simplistic explaination makes sense!

Regards

Brendan

Thanks, I appreciate it!

Originally Posted by mcrover

If it makes it harder to steer then there are other problems because it shouldn't, maybe crook CV's or something.

Urmmmm that would be why you dont lock it as soon as you engage low box, the diff in there is plenty strong enough as its got at least a 3.54:1 mechanical advantage that the other diffs dont have.

Ive seen plenty of diffs, half shafts and propshafts knackerd (not necissarily broken but definatley beyond acceptable wear limits) because of people operating the CDL when it wasnt required.

the CDL is there to eliminate driveline wind up... if your finding it hard to steer you have windup happening, and thats bad.

Originally Posted by mcrover

Because it puts too much torque through the cross pin in the centre diff.

If your backing a trailer up a driveway or the like and only for a short distance it is better to use the CDL as it will take a lot more than that pin.

It is only a 2 pinion diff centre in the centre diff and I have seen 3 now that have either broken the pin or cracked pinions in non 4wd applications, 2 were backing trailers, 1 car trailer up a steep driveway and 1 caravan through a drain into a site and 1 that was just full noise stupidity taking off from the lights in Low range no CDL and the inevitable happened.

I didnt do the repairs but I did see the damage done.

Does that cover it

fair enough i thought you were just talking about in off road situations i forget about the hole towing thing......but even so engaging the centre on the black top towing or not i thought it causes transmission wind up..

(not trying o catch you out by the way just trying to understand this whole transmission things doesn't come naturaly to me)

the basic rules I try to squeeze into the basic drivers is this..

on road CDL off high range
reversing cdl off low range
off road high speed where traction is good CDL off tyres just below road pressure
off road high speed loose gravel/clay/sand cdl on range as appropriate for speed and drop the tyre pressures.
if your crossing axles or lifting tyres low range, CDL on, tyres at mid pressure and 1st/2nd/Rvs gears only.

beach work/loose sand, tyres right down, low box top 3 gears and CDL on.

that covers about 90% of the circumstances you will normally find yourself in, after that its an experience thing.

Originally Posted by Blknight.aus

the basic rules I try to squeeze into the basic drivers is this..

off road high speed loose gravel/clay/sand cdl on range as appropriate for speed and drop the tyre pressures.


beach work/loose sand, tyres right down, low box top 3 gears and CDL on.

that covers about 90% of the circumstances you will normally find yourself in, after that its an experience thing.

Just a couple of points Dave.

What do you mean by high speed on loose gravel/clay etc?

You have forgotten wet grass, low box top 3 gears. Wet grass is almost as slippery as ice.


I was taught used CDL at low speeds and take it out ASAP/when crossed slippery ground. CDL can be put in/out on move.


Please remember I am UK based/European experience so not used to Australian conditions etc and want as much info as possible before I get there.


Regards


Brendan

i engage mine as soon as i leave the black top

i just find it more driver friendly on dirt or loose surfaces

Originally Posted by leeds

Just a couple of points Dave.

What do you mean by high speed on loose gravel/clay etc?

in Aus we have a lot of "outback highways" that are a good firm surface but dont have bitumen on them but if you want me to pluck some numbers Id say if your doing over 50 then youhave no need for the CDL.

Originally Posted by leeds

You have forgotten wet grass, low box top 3 gears. Wet grass is almost as slippery as ice.

not something your likely to encounter here we have a different soil base to you guys but if treat it like wet clay, low box, umm lets say second gear for some torque limiting and CDL on

Originally Posted by leeds

I was taught used CDL at low speeds and take it out ASAP/when crossed slippery ground. CDL can be put in/out on move.

yep thats about right but remember that it doesnt always disengage if the driveline has wound up

Originally Posted by leeds

Please remember I am UK based/European experience so not used to Australian conditions etc and want as much info as possible before I get there.


Regards


Brendan

no problems there, as a fair warning our ground changes state to state and sometimes township to township. what works in the NT is not guarenteed to work in victoria.

hope to catch you on the trip.