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rear diff wound up

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wizard:
Here,s a bit of info i borrowed from somewhere. :shock:



When a 4WD is travelling in a straight line all four wheels rotate at the same speed, but during cornering each wheel travels at a different speed due to the radius of the turn. All vehicles have a differential on the front and rear axles to allow the wheels on the same axle to rotate at a different speed. Constant 4WD’s have a central differential fitted  to allow for different speeds between front and back wheels, but most part-time four wheel drives do not.

When a part-time 4WD (without a centre differential) is in 4WD an attempts to corner on bitumen, all wheels need to rotate at different speeds, but without a centre differential they cannot. This creates the phenomena called "axle windup" or "transmission windup". High strain is placed on the drive shafts and transmission, eventually causing one of two things to happen. Either one of the wheels slips or spins to overcome the stress or the drive-shaft/transmission breaks. This is why part time 4WD’s should never select 4WD on bitumen.

Constant 4WD’s have a central differential within the transmission to overcome this problem. However once in the dirt a constant four wheel drive can be bogged with only one wheel spinning. This is why they have a central differential lock that stops the action of the centre diff and makes it like a part-time four wheel drive in 4WD mode. The centre diff lock should never be used on bitumen or non-slip surfaces for the reasons mentioned above.

In reality, a 4WD is only a two wheel drive with one front and one back wheel driving when traction is lost. One wheel on each axle spins while the other receives no drive at all due to the action of the differential. The exception to this is where a limited slip or locking differential is fitted. A limited slip diff allows a limited amount of drive to be applied to the stationary wheel before the other wheel on the same axle spins. A locking diff allows no slip at all and both wheels on the same axle turn at the same speed, regardless of the amount of traction



wizard :twisted:

Range Rover Blues:
I was with it up to the last paragraph, a 4wd is really a 2wd :-., then surely a 2wd is really a 1wd et al.  The point of 4wd is that provided only 1 axle is in the puddle at once you never notice the loss in grip, that and the amount of power availbel is spread between twice as many wheels to reduce the chance of wheelspin.

Anyhoo, back to the question at hand, windup.  In degrees how far will the transmission wind up before it breaks? does anyone know :-k

wizard:
4WD is a bit missleading. If you have front and rear lockers and a center diff then you really are 4WD Most 4x4's are effectively 2wd because if you engage the center diff and lift a wheel on each axle off the ground (cross axled) you wont go anywhere because the drive (power) takes the path of least resistance.
Winding the diff up is also not totally accurate, but transmission wind up is.

I dont know how much "windup" is required to cause any damage.
To test this we need a volunteer to engage diff lock and  record the mileage on tarmac before something brakes. (only joking)


wizard

carracarra13:
you paying for fixes lol :lol:

Disco Matt:
The impression that I get from various magazine letters pages is that you would notice before breaking something. The steering will feel very odd and it won't want to turn tightly.

I know that if I'm on a loose but dry surface like gravel I tend not to use the diff lock, as it makes the car reluctant to turn in.

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