diff lock hows it work??????

[chris abell]

i recently bought a 300tdi 1994 disco it is my first 4x4 and i didnt know any thing about how the 4x4 works the warning light on the dash was flashing it came on for a few seconds then went off for a bit when we went out on road test i asked what it was and the guy i bought it from said that it was just a loose wire to the diff lock and nothing to worry about i asked if he could show me the 4x4 working he pulled over and engaged the small stick in low gears and then high and i thought that it was all working properly any way i bought the vehicle but when my friend looked at it a few days later the diff light on the dash had started to stay on and was concerned that id been running it in diff lock but the gear stick is in the normal driving high gear?. but when i engage it into the diff lock gear the car just drives as it would in the high gear theres no change as i was told you can really tell when you drive in diff lock that the car has a lot more torque and wont go much over 30 mile an hour so i wondered if my transfer box is knackered i just wondered if anyone knew what the problem may be????. thanks for reading this and hopefully replying. :rolleyes:

[swag298]

Pushing the small stick all the way to the left locks the centre diff.
It will do this in high or low range.
Low range (Stick all the way forward) is what gives you the lower speeds and increased torque at the wheels.
High range is stick all the way to the rear. That's your normal gears.
Diff lock locks the front and rear propshafts together. You should only use this in situations where you would be likely to lose traction....wet grass, mud, gravel etc.
Your Discovery is permanent 4 wheel drive. The centre diff allows the front and rear axles to travel at different speeds such as when cornering. The front axle travels further around a corner than the rear, so has to spin faster.
You can possibly damage the driveline by using diff lock on hard, or high traction, surfaces.
To check whether it's working properly jack one wheel up off the ground.
With the diff un-locked (Stick to the right), hand-brake off, main gear lever in neutral you should be able to rotate that one wheel by hand.
If you then lock the diff by pushing the stick over to the left, you should find that the wheel will lock up. It may take a revolution or 2 for the diff to actually engage.
Then un-lock the diff again and check the wheel can be rotated again.
If all that's OK then it's an electrical fault.

swag

[chris abell]

thanks very much for that ill give it a go tomorow, much appreciated
chris:)

[oRGie]

welcome to the forum :)

you have 3 diff's and 2 gearboxes.

Front diff (in middle of front axle), rear diff (in middle of rear axle) and the centre diff. A main gearbox and transfer gearbox.

you have 2 main gear ratio's suplied if you like by the transfer gearbox.
High (for normal road use and easy going off road) and
low (can be used on road if trying to move a heavy trailer eg but mainly used in the sticky stuff or very steep hills)

as standard you only have a diff lock for the centre diff. With the diff un-locked (normal road use and easy going off road) the front and rear axles are able to turn at different speeds, this means you won't get transmission windup when turning corners etc, same function as the diff in any vehicles axle, it allows you to go round corners, or to let the wheels on either end of the axle turn at different speeds, but in the case of a permanent 4x4 the front and rear axles can turn at different speeds.

when locked, the power is sent evenly to the front and rear axles, this means that if a wheel loses traction you will still have drive to the wheels on the other axle, if the diff was not locked then 1 spinning wheel would leave you stuck !

Bear in mind that if you dont have diff locks in the front and rear axles (aftermarket fit only) and your centre diff is unlocked 1 spinning wheel and you stop, if the centre diff is locked then it takes 2 spinning wheels (1 on front axle and one on back) for you to get stuck. If you want a true 4 wheel drive, then you need to install front and rear diff locks, lock all 3 diffs and you will keep going till all your wheels lose traction.

so you should only lock a diff if the surface your driving on is slippery or dusty, sand sort of thing, this allows the wheels to spin rather than your transmission getting wound up.

you can use high or low box on or off road with no problem with the centre diff unlocked.

Its not so easy to tell if your centre diff is locked or not by just driving along, if you had diff locks in the front or rear axle, that would be easy to tell and you would feel the resistance when on road while trying to turn, but the centre diff isnt so easy to feel ! the best way to find out is to jack a wheel off the ground, if the diff is unlocked you should be able to spin the wheel by hand whilst it is in gear, if you cannot it means your centre diff is locked.

Often on many centre diffs, they dont disengage as soon as you move the lever, I found that after moving the lever to unlock the centre diff, drive forward a bit, then go into reverse and reverse a bit, this usually unlocks the diff. (this should not be nessecary and not in all LR's, but I found it works well, I prefer it to driving along slowly till it decides to unlock)

simple ;) :rolleyes: :D


edit: lol, took me too long to type, beaten to the post ;)

[Geobloke]

excellent descriptions though Peeps! :yay:

[jen.s.f]

A very usefull thing to have if you find yourself in a situation where you have one wheel off the ground and can't go anywhere. Engage diff lock and off you go, not forgeting to unlock it as soon as poss.

[Widget]

To check whether it's working properly jack one wheel up off the ground.
With the diff un-locked (Stick to the right), hand-brake off, main gear lever in neutral you should be able to rotate that one wheel by hand.
If you then lock the diff by pushing the stick over to the left, you should find that the wheel will lock up. It may take a revolution or 2 for the diff to actually engage.
swag

:confused: Confused. Surely even with the centre diff locked the wheel still spin? After all there is an open diff on the axle. As oRGie says...

if the centre diff is locked then it takes 2 spinning wheels (1 on front axle and one on back) for you to get stuck.

...one wheel on each axle will rotate with the diff locked.

If you jack up one wheel and try to drive off - it will spin the wheel if the centre diff is not engaged, but drive off if it is engaged.

[jen.s.f]

"If you jack up one wheel and try to drive off - it will spin the wheel if the centre diff is not engaged, but drive off if it is engaged."



Hence the reason it's usefull when you get stuck with one wheel off the ground!!

[swag298]

:confused: Confused. Surely even with the centre diff locked the wheel still spin? After all there is an open diff on the axle.

If you've got one wheel jacked up, diff locked, and you try to rotate it you find that it has locked.
The open diff in the axle would try to rotate the propshaft becasue the wheel on the other end is on the ground.
Because both rear wheels are on the floor, the rear prop can't move. Because the centre diff is locked that means neither can the front prop, hence neither can the front wheel.

swag

[swag298]

...one wheel on each axle will rotate with the diff locked.



That would happen if you jacked up the wheel on the opposite corner aswell.
With the diff locked, one wheel on each axle CAN spin, but only opposite corners, and only simultaneously.

swag