[email protected] wrote:
> I've done a search on google but can't find an answer to this
> particular problem.
>
> I have an 89 3.5 efi Range Rover.
>
> The High / Low ratio selector is very stiff to operate, is there a way
> to grease or free this?.
>
Quite simply use it more frequently! Try engaging and disengaging it
several times each time you use the vehicle. Make sure that the lever
travels far enough to actually engage something, if you see what I mean.
Ignore the warning lights, more on that later. The movement should free
up with use.
At this point it might help to explain that the 'system' has two parts -
an external linkage directly connected to the lever and a dog clutch
which is directly linked to the warning light. There is a compression
spring between the two parts which allows them to move independantly.
In most cases the external linkage seizes through lack of use. If
exercising it as above fails to provide relief, get underneath and
lubricate the linkage with diesel, WD40 or similar. Try to get the
lubricant to the shaft which passes into the front output housing
underneath the rotating lever. Repeat the exercising.
> I also have a potentially more serious problem.
>
> With a lot of pressure (on the lever) I am able to select the diff lock
> position, and the orange light comes on (not always immediatley,
> occasionally i have to drive a few metres).
>
> When i want to disengage the diff lock, the orange light does not go
> out immediatley.
>
> The last time i tried this, i had to drive 3 or 4 miles before the
> light went out.
>
> Its quite obvious from the way the RR drives that the diff lock is
> still engaged.
>
> Can anyone tell me how to fix this problem.
>
This is the result of a lack of understanding of what is happening
underneath. It has nothing to do with the selection part of the system
but with the dog clutch part. The dog clutch is unaffected by
infrequency of use.
The dog clutch has a sliding part and a fixed part. The sliding part is
moved by the selector lever but there is a compression spring between
the two. This means that the lever can be pushed fully into a selected
position compressing the spring but the sliding member need not move
unless it is free to do so.
The illuminated warning light effectively indicates that the sliding
member is in the locked diff position. The illumination state will not
change until the sliding member moves and from the previous paragraph
this need not be when the lever is moved.
All this part of the system is obviously working as your light goes on
and off and you have observed that driving on hard surfaces with the
diff lock engaged is 'different'. The good news, then, is that there's
nothing wrong inside!
For the dog clutch to engage i.e. actually apply the differential lock,
teeth on the fixed and sliding members need to mate and this will not
happen if the teeth are butting up to each other. Some relative movement
between the teeth is required to allow a tooth in one part to line up
with a 'hole' in the other part. It actually requires the teeth to move
relative to each other so sitting stationary does not help - actual
road wheel rotation is needed to provide relative rotation between the
front and rear propshafts. When the tooth and 'hole' are lined up the
sliding member is free to engage with the fixed member under the force
of the compressed spring.
Once engaged, torque in the driveline (either wind-up or driving torque)
will keep this dog clutch engaged through forces on the teeth. These
forces must be reduced (to near zero) to allow the dog clutch teeth to
be separated - again by a compressed spring. This explains the delay or
refusal to disengage. It is perfectly normal behaviour. Nothing is wrong.
To accomplish disengement do not drive steadily - this maintains the
torque that you do not want. Sequential acceleration and deceleration
will often bring about disengagement.
If that fails:
Either
Drive in reverse, possibly turning the steering one way as you do
so. You're relying here on free play in the driveline, tyre deflections
and differing rotational speeds between the front and rear propshafts.
Or
Allow a road wheel to slip in relation to the other three. Try driving
on the grass verge (better if soft and wet) or drive sharply off a kerb
or over a sharp bump. You're trying to get any one wheel to lose
traction momentarily.
If you are absolutely stuck and wish to release the diff lock whilst at
home, jack up a wheel which will 'kick' a bit when contact with the
ground is lost. The handbrake should be released for this operation so
take appropriate precautions (obviously not using the wheel brakes
either) against the vehicle moving.
Prevention is better than cure - avoid driving on hard surfaces with the
diff lock engaged. That way you'll avoid the wind-up which is the cause
of your problem!
