front prop off no go.Why?

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gotoneatlast

gotoneatlast

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Location
berkshire,uk
i was checking today if my clutch was working having bled it.
Having not replaced the front prop shaft, i noticed that the car wouldn't move fwd, and recalled reading somewhere that it won't unless i engage difflock, as my diff lock doesn't work, i had to forget about this and checked by watching the flange rotate on the transfer box.
My question is this, as the disco is permanent 4WD, although not good for the car, why doesn't it move with only the rear prop attached, how does difflock govern this?
 
A differential will always pass it's rotation through the path of least resistance.
No front prop and no diff lock, means front output flange spins and back wheels dont!

The center difflock will lock the differential so it passes equal rotation to each output flange.
 
cheers,
really simply put.

is the power distribution different then between front and rear props without difflock, given the longer rear prop?
 
nothing to do with the longer shaft, think of the cornering and the arcs scribed by the wheels when you do...

each arc is a different length. so would need different amounts of rotation to compensate...

Hence a 'differential' gear....

One in each axle and one between them.
 
Prop length has nowt to do with it, however when you turn a corner the rear wheels will travel a shorter distance than the front... hence why you need a centre diff!
 
yeh i got you,
otherwise you'd be dragging the back wheels round the corner having made it with the front.
Is power or drive from engine split 50/50 to the front and rear axles though, and/or is the gearing in the front and rear diffs of different sizes?
 
gotoneatlast said:
yeh i got you,
otherwise you'd be dragging the back wheels round the corner having made it with the front.
Is power or drive from engine split 50/50 to the front and rear axles though, and/or is the gearing in the front and rear diffs of different sizes?
Click to expand...

Not strictly true.
think of it as rotation, not power!

roatation is split at the transfer box to each axle though a diff, then again in each axle though a diff to each wheel.
 
the only way to truly understand a differential gear is to have a look at one.

they are a very simple arrangement, but very clever in what they do, as they allow an infinate variable in 'Difference'

see if you can search out an online animation...
 
battenberg said:
Not strictly true.
think of it as rotation, not power!

roatation is split at the transfer box to each axle though a diff, then again in each axle though a diff to each wheel.
Click to expand...

Before you go and do something interesting is the rotation you talk off Torque?

Thanks, for all of that,
sorry lerk!! keeps you mind active though!,

I promise i'll leave it there today.
 
gotoneatlast said:
Before you go and do something interesting is the rotation you talk off Torque?
Click to expand...

no, torque is the force behind the rotation and measured in this way...

take ratchet bar 1ft long and use it to tighten a bolt, add 1Lb of weight to that bar, you have tightened your bolt to a torque of '1footpound' or '1 ft·lbf'

now stick 100Lb's of weight on the same bar, you have tightened up your bolt to '100footpounds'.

other measurements could be "Newton Meters" or "Nm's"

Apply that now to the output shaft of your engine, the torque figure is the force behind the rotation of the shaft... not the actual rotation
 
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