Locked diff

Hi all,
Ok, maybe i'm a retard but can someone please explain the following to me:

I know that a defender is constant 4wd, i also know that in normal driving that one wheel will start to spin (ie in snow) first before the others, and/or to help day to day driving.

Now this is where I get confused:

Whilst towing a guy out of the snow yesterday. I put me landy into low box, and locked diff. I finally got him out, however a mate of mine who was watching noted that the front and back offside wheels were spining but the nearside wheels did not.

Now I thought when in locked diff, all 4 wheels would either give traction or spin?

So me being me I had to see this for meself, so we tied a robe from the landy to a tree and me mate pulled on the rope with the landy and the same thing happended again. IE offside front and back wheels spun, nearside didn't move. It gave it more welly and the offside front spun and the nearside rear wheel spun, ie the other 2 didnt move.

Why is this? I thought when we connected the rope to the tree and gave it some, all 4 wheels would have spun on the snow.

Please explain

nope
do ya know how a diff works?

if so the diff lock only locks the diff in the transfer box - yu still have normal diffs in each axle.

Hmmmmm,

I think I do now, just did a search.

Yeah I know I'm a dumb f**k. But I aint much of a lateral thinker. I thought locking diff meant locking all 4 wheels together. ie so they couldn't turn individually.

No wonder i can go around corners easily with diff locked .
What I can't understand is why other 4wds shake and skid like hell when they are in so called locked diff 4wd.

Diff lock on a landy only locks the propshafts together. So you can become cross axled as you did on the snow, Most slitty 4x4's with difflocks tend to have them on the axles. which prevents the wheels spinning at different speeds.

redhand said:

Diff lock on a landy only locks the propshafts together. So you can become cross axled as you did on the snow, Most slitty 4x4's with difflocks tend to have them on the axles. which prevents the wheels spinning at different speeds.

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Ok, .......... does that mean then that a slitty 4x4 would hold traction longer than a defender when pulling on ice etc?

Think of the transfer box like a third diff.
Normally it gives drive to both axles (either high or low range) but the available drive will always take the easiest route which means if you get a wheel in the air (or in a hole) that wheel will spin and drive to the other wheels is all but lost.
When you use diff lock it focres the available drive to both front and rear axles but the available drive will still try to take the easiest route which is what happened to you when you had one front and one rear wheel spinning. So long as you are on slippy ground you will be able to make turns without the juddering which is also known as tranmission wind-up.
If you have locking diffs (either mechanical or air controlled) or limited slip diffs in your axles the available drive will be shared equally to all wheels provided the central diff (xfer box) is locked. In this mode it is very hard to make turns.
Modern Jap 4x4s use various methods to simulate locking diffs but the most common is the application of the brake (by clever electronics) to the spinning wheel(s) to force the drive back to the other wheels on the same axle.
In 4wd cars such as Subarus they often use a viscous clutch to emulate a transfer box but these have no provision for high and low range selection.

Shifty1962 said:

When you use diff lock it focres the available drive to both front and rear axles but the available drive will still try to take the easiest route which is what happened to you when you had one front and one rear wheel spinning. So long as you are on slippy ground you will be able to make turns without the juddering which is also known as tranmission wind-up.
.

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Thanks for the answer, but what you state above was the bit that worried me to a point in the first place.

IE Slippery road conditions or not, when I lock diff, you would never know it was locked when turning sharply. There is no juddering at all and thats what worried me because I thought that would happen.

Wozy said:

Thanks for the answer, but what you state above was the bit that worried me to a point in the first place.

IE Slippery road conditions or not, when I lock diff, you would never know it was locked when turning sharply. There is no juddering at all and thats what worried me because I thought that would happen.

Click to expand...

Thats why you have the light to tell you that you have engaged difflock.

Wozy said:

Ok, .......... does that mean then that a slitty 4x4 would hold traction longer than a defender when pulling on ice etc?

Click to expand...

In theory, possibly. In practise they are often fitted with a rear diff lock because they are a lot lighter and on stiff cart springs, so have less grip & are more likely to spin the rear wheels.
Bear in mind until recently most slitties were selectable 4wd

Wozy said:

Thanks for the answer, but what you state above was the bit that worried me to a point in the first place.

IE Slippery road conditions or not, when I lock diff, you would never know it was locked when turning sharply. There is no juddering at all and thats what worried me because I thought that would happen.

Click to expand...

If you were to drive around in tight circles you would have a problem.
During normal driving and turning the diffs and the tyres scrubbing are allowing the wheels to turn at different speeds and trans wind-up is not likely to be a big problem. Which is what you are finding. The effect would be more pronounced with wider tyres giving more grip on dry surfaces.
The time to be careful is whilst in low range as the huge increase in torque to the drive wheels will quickly find a weakness in halfshafts, UJs, or diffs resulting in a very loud bang and a very painful wallet.