Difflock stuck

We've been here several times before and I'd hoped to have been able to find one of my past treatises on the subject - so far without success.

Firstly how are you defining engaged and disengaged? The warning light is a true indication (assuming that it works!), the position of the selector lever is not.

It's usually impossible to select and subsequently disengage the diff. lock when stationary. You might get the lever to move fully into both positions but the actual lock is unlikely to change state.

If you remember that the lever only sets up the conditions for the diff. lock to engage you won't go far wrong. Obviously, and this seems not to be the case here, the linkage is seized you won't move the lever and the lock stays in the state that it's in.

Slowness to engage is because the lock dog clutch teeth may be end-to-end and not engaging, There needs to be relative rotational movement to allow the teeth to engage and hence engage the lock. This usually happens after a very short driving distance

Once engaged the usual difficulty is that the lock dog clutch will not disengage under torque. This could be because you are driving or on the overrun - accelerating or decelerating may bring about the result you require. The other common possibility is wind-up caused by driving around with the diff. lock engaged under conditions which do not allow the wheels to slip. Rocking backwards and forwards is unlikely to work: driving a short distance backwards and forwards might. However the easiest way is to drive with at least one wheel on some soft ground or drive off a kerb fast enough that a wheel momentarily loses contact with the ground.

Hope that you find something there helpful.

We've been here several times before and I'd hoped to have been able to find one of my past treatises on the subject - so far without success.

Firstly how are you defining engaged and disengaged? The warning light is a true indication (assuming that it works!), the position of the selector lever is not.

It's usually impossible to engage and subsequently disengage the diff. lock when stationary. You might get the lever to move fully into both positions but the actual lock is unlikely to change state.

If you remember that the lever only sets up the conditions for the diff. lock to engage you won't go far wrong. Obviously, and this seems not to be the case here, if the linkage is seized you won't move the lever and the lock stays in the state that it's in.

Slowness to engage is because the lock dog clutch teeth may be end-to-end and not engaging, There needs to be relative rotational movement to allow the teeth to engage and hence engage the lock. This usually happens after a very short driving distance

Once engaged the usual difficulty is that the lock dog clutch will not disengage under torque. This could be because you are driving or on the overrun - accelerating or decelerating may bring about the result you require. The other common possibility is wind-up caused by driving around with the diff. lock engaged under conditions which do not allow the wheels to slip. Rocking backwards and forwards is unlikely to work: driving a short distance backwards and forwards might. However the easiest way is to drive with at least one wheel on some soft ground or drive off a kerb fast enough that a wheel momentarily loses contact with the ground.

Hope that you find something there helpful.

And it won't help if you have any odd sized tyres fitted.

What Dougal says ... ;)

When I'm engaging/dis-engaging difflock i always keep the vehicle moving. If it doesn't want to disengage, I find that (as D says) accelerating helps especially if you turn at the same time. You need to get relative movement between front and rear axles so the diff moves, so stationary won't do it ... ;)

Thanks to all for the input

If it still won't disengage, raise a wheel either by jacking it up with the bottle jack or cross-axling the truck, on loose surfaces make the wheels spin or skid by accelerating or braking, but if it's properly stuck on then it's spanner time. If it just won't disengage by cross-axling, skidding or accelerating then the bottle jack will do it if there's no fault so don't give up and reach for the spanners until you've jacked up a wheel and wiggled it. If jacking doesn't work then you've got a problem, might be the linkage as suggested.

Best jack up a front wheel as you can do that with the handbrake on to stop the truck moving, and still move the diff by wiggling a front wheel.