Thread: What's the consensus on.........

CDL on gravel roads won't cause or prevent clutch failure.

Hi,

Interesting this crops up from time to time:

Diff Lock in or out on dirt

Frank's earlier comments re: D1 owner's manual CDL instructions for use are somewhat different from a 74 RRC.

The instruction plaque under the heater controls in my 74 is very clear in stating that the CDL should only be used when traction is lost at one or more wheels and should be disengaged immediately traction is regained.

It also says that wide throttle openings should not be used in 1st or 2nd low range with the CDL engaged to avoid unnecessary wear and possible damage.

Cheers, DL

Originally Posted by 350RRC

The instruction plaque under the heater controls in my 74 is very clear in stating that the CDL should only be used when traction is lost at one or more wheels and should be disengaged immediately traction is regained.

It also says that wide throttle openings should not be used in 1st or 2nd low range with the CDL engaged to avoid unnecessary wear and possible damage.

Cheers, DL

The instruction plate in my 85 says to avoid wide throttle openings in low range first and second gear. But doesn't refer to the CDL in that same sentence or mention wear/damage.

The use of CDL in any gear on loose surfaces enhances handling (it's the same effect as engaging 4WD with locked hubs in, in a non-centre diff (eg. older type Jap) 4WD vehicle)

What you say may be correct with loose surfaces and since I am familiar with the road Tank is talking about, I can see some reasons to engage the CDL on that particular road.

However, I remain to be convinced that the CDL should be engaged every time you leave the bitumen. I know that a lot of dirt roads have significantly reduced traction. I have heard that the WA roads with pea gravel or whatever it is called, are diabolical.

Maybe I am misunderstanding some people's comments but it sounds as if their argument is that any dirt road needs the CDL engaged.

The reason I wonder about that approach is that I have driven on dirt roads that I swear had as much traction as some bitumen I have driven on, especially once the bitumen gets a bit of oil and/or moisture.

When I was racing motorcycles on short circuit tracks, there were some old, established tracks where the surface was so hard packed and polished that I could hear my rear tyre squealing as I came into the corners. I bet some bitumen has less grip than that. I bet that if I drove on a surface like that with the CDL engaged, that it would take forever to disengage when I moved the lever back.

I hope that when people say that the CDL should be engaged whenever you leave the bitumen, that they are not thinking of that sort of surface. I said much earlier that if the surface is such that the CDL won't disengage, then surely there is no need for the CDL to be locked. If it won't disengage as you continue to drive, surely that is proof that there is no slippage at all. In which case, how is it different from driving on bitumen?

I worry that blanket statements like, "I engage the CDL every time I am on a dirt road", are open to misunderstanding. I wouldn't like to think that some novice reading the comment would assume that it means that the CDL should be locked even if the dirt provides the same sort of grip as a bitumen road.

Originally Posted by vnx205

Maybe I am misunderstanding some people's comments but it sounds as if their argument is that any dirt road needs the CDL engaged.

What I suspect we're seeing is more regional variation in dirt roads than anything else.
Those that drive on loose surface dirt roads more than likely lock it up. Those that drive on high traction dirt roads likely don't.

I get all types. The public dirt roads are gravelled and normally very loose where locking up the CDL gives far better directional stabililty. But occasionally in winter when they're carrying more moisture they can compact to a smooth and firm surface with plenty of traction.
The private dirt roads are usually hard and dry. Little gravel and normally good traction until they get steep.

As you know, if you've got ample traction, there is nothing to be gained by locking it.

Originally Posted by 350RRC

Hi,

Interesting this crops up from time to time:

Diff Lock in or out on dirt

Frank's earlier comments re: D1 owner's manual CDL instructions for use are somewhat different from a 74 RRC.

The instruction plaque under the heater controls in my 74 is very clear in stating that the CDL should only be used when traction is lost at one or more wheels and should be disengaged immediately traction is regained.

It also says that wide throttle openings should not be used in 1st or 2nd low range with the CDL engaged to avoid unnecessary wear and possible damage.

Cheers, DL

I was told by a reliable source that they had to change the plaque due to people burning up the centre diff from not engaging it until traction was lost, ie the vehicle now not moving.

As to the amount of traction difference between even a good hard dirt/gravel road and a bitumen road, the easy way to check is accelerate up to 60k's or so and jump on the brakes and see how long/far it takes to stop, then try the same on a Tarmac lined road.
There is not a dirt road that has the same level of grip as a tarred road, and whether you can feel or sense whether your wheels are slipping or not, an unlocked CD is going to work harder on dirt that it does on tar. The reason Allan for the diff winding up is because with the CDL engaged one axle (front or rear) may slip while the other isn't slipping.
It is natural for there to be some windup, which can be alleviated, as you know, by backing up a bit.
And as for Dougals sweeping statement "CDL on gravel roads won't cause or prevent clutch failure."
Please enlighten us how you KNOW this, seeing as I did NOT say this was the case, Regards Frank