C.Diff Lock Issues / Test?

[manic]

I locked the center diff on my 90 when jacking up to do the rear brakes... before I drove round the block to test my brakes I disengaged the diff lock and the light on the dash went out.

On the drive I still had some issues with the brakes rubbing so back in the garage jacked one of the rear wheels back up to have a look, this time not bothering to re-engage the CDL, happy with my chocks.

Now then shouldnt the one wheel in the air be able to rotate if the CDL is not engaged - is that not the test to see if CDL is working?

I know its not the brakes because I cant rotate it even when they are removed.

So looks like my CDL is still locked even though I pushed the stick across to disengage it and the light went out!? I thought I could trust that blasted light.

[goingbush]

If the main gearbox is in gear the wheel won't turn.

If the handbrake is on the wheel won't turn

The only way to test if the CDL is engaged is to jack up one wheel,
Handbrake OFF, Main Gearbox OUT OF GEAR .


With CDL engaged jacked up wheel won't turn
With CDL disengaged wheel will turn, again gearbox must be in neutral , (unless you have the strength to turn the engine over by turning the wheel)

regardless of wether light is on or off, its where the lever is that matters.

[manic]

putting it in 1st when parking up is a subconscious habit of mine...

sorted

[vnx205]

... ..... ....

regardless of wether light is on or off, its where the lever is that matters.

In this context, that is probably a fair comment, but when driving the opposite is true.

After driving with the CDL locked, if the lever is moved to the unlocked position, the light can stay on for some distance on some surfaces. It stays on because the CDL is still locked.

It isn't unlocked until the light goes out.

[Bush65]

...

regardless of wether light is on or off, its where the lever is that matters.

Not quite correct!

The part that actually locks the diff is pushed into the lock position by a spring. The lever only pushes on one side of the spring and doesn't guarantee that the spring pushes the locking part - often this part is prevented from engaging if the plunger in the switch is stuck or adjusted down too far. I'm pretty sure they did it this way to avoid the problem of wanting to move the lever to the lock position when the mating teeth aren't lined up to allow engagement - later when the mating parts turn to a position where they can engage, the spring does its job.

Although the lever position doesn't ensure the diff is locked, nearly always it will be locked when the light is on. I say nearly always because I now of one Disco I that even with the lever in lock position and light on, the diff wasn't locked - the owner took the vehicle to his mechanic who rectified it but the owner doesn't know what was done. I suspect adjustment of the switch height.

For the original poster with the unlocking problem, the diff should be unlocked when the light goes out. Perhaps something is broken inside the diff and fragments are causing it to lock - they can and do break the cross pins, the thrust washers wear affecting gear tooth engagement, which can lead to broken teeth.

[manic]

In this context, that is probably a fair comment, but when driving the opposite is true.

After driving with the CDL locked, if the lever is moved to the unlocked position, the light can stay on for some distance on some surfaces. It stays on because the CDL is still locked.

It isn't unlocked until the light goes out.

yes I've noticed this - sometimes I reverse a bit to get CDL to fully disengage...

as far as I know the cdl light switch screws into the transfer housing and is pushed on by something mechanical in the transfer case that indicates in all probability that the cdl is locked.... unlike your average reverse switch that is triggered by gear stick position and can go out of 'sync' the CDL light switch is fixed and triggered by the transfer box internals so should be very trustworthy so long as it is going on and off.. faith restored.

[manic]

Not quite correct!
For the original poster with the unlocking problem, the diff should be unlocked when the light goes out. Perhaps something is broken inside the diff and fragments are causing it to lock - they can and do break the cross pins, the thrust washers wear affecting gear tooth engagement, which can lead to broken teeth.

err no, the original poster forgot he was parked in first gear!

[labrado]

[QUOTE=Bush65;1685498]Not quite correct!

The part that actually locks the diff is pushed into the lock position by a spring. The lever only pushes on one side of the spring and doesn't guarantee that the spring pushes the locking part - often this part is prevented from engaging if the plunger in the switch is stuck or adjusted down too far. I'm pretty sure they did it this way to avoid the problem of wanting to move the lever to the lock position when the mating teeth aren't lined up to allow engagement - later when the mating parts turn to a position where they can engage, the spring does its job.


I observed sometimes after I push the lever to the left, the diff light will not be on until the car moves forward a few meters. Is it caused by the spring you mentioned? I'm a layperson in terms of car mechanics.

[Bush65]

Not quite correct!

The part that actually locks the diff is pushed into the lock position by a spring. The lever only pushes on one side of the spring and doesn't guarantee that the spring pushes the locking part - often this part is prevented from engaging if the plunger in the switch is stuck or adjusted down too far. I'm pretty sure they did it this way to avoid the problem of wanting to move the lever to the lock position when the mating teeth aren't lined up to allow engagement - later when the mating parts turn to a position where they can engage, the spring does its job.

I observed sometimes after I push the lever to the left, the diff light will not be on until the car moves forward a few meters. Is it caused by the spring you mentioned? I'm a layperson in terms of car mechanics.

For the sliding part that locks the diff to engage, the mating teeth have to be aligned.

If the mating teeth are not in the aligned position, the spring allows you to push the lever fully to the left, and once the mating parts rotate to where the teeth can engage, the spring proceeds to push the sliding part to the locked postion. The sliding part pushes the plunger in the switch above it, as it moves to the locked position.