Black Magic Diffs

[jims-terrano]

Can anyone explain in very easy terms how diffs work and the differences in diffs and diff locks.
I get the principle that as you go around a corner one wheel is bound to turn at a different speed to the other and even then I’ve no idea how that works.
I know that if one wheel loses grip then it spins and the opposite wheel just doesn’t turn? How on earth is that supposed to be helpful?

I’ve always just accepted that they are black magic but just been watching a crazy russian YouTube channel and today they welded up the diff on a fwd drive lada and went for a drive around. It was hell to steer but it really improved driving in snow.

[solarman216]

Not difficult at all, an open diff is just that a diff that allows different rotational speeds between inside and outside road wheels, but if one wheel is on slippy ground then that wheel will spin and the wheel on good ground will have no traction, so you are stuck, with a limited slip diff then subject to how much the clutch plates are designed to bite then at least some traction will be applied to the good grip wheel, but in my experience not usually enough to get you out of trouble, now a diff lock is the bees knees engage that and both wheels will turn no matter what, but get onto hard ground do not expect to be able to go round corners without something giving, usually jumping rear wheels under strain, Rick

[jims-terrano]

Thanks Rick so the crazy russians that welded their diff actual created a locked diff.
I agree about the terrano diff, I remember a long time ago when one of my front hubs wasn’t working I got stuck in mud and one rear wheeel span like mad and the other just sat there stationary.

[terranosaurusdoug]

Originally Posted by jims-terrano

Thanks Rick so the crazy russians that welded their diff actual created a locked diff.
I agree about the terrano diff, I remember a long time ago when one of my front hubs wasn’t working I got stuck in mud and one rear wheeel span like mad and the other just sat there stationary.

YouTube is your friend on this one mate it's all about the spider gears bud x

[Jay666d]

My favorite diff video on YouTube: https://youtu.be/yYAw79386WI

[jims-terrano]

Thanks Jay, I still find the idea complicated so I’ll just accept that it works in the same way that I accept the wife is always right

[Lazy-Ferret]

I remember my first Mecano set, and one of the first things the instructions get you to build is a Differential.

I must have built goodness only know how many and had no idea what they were for.

I went to automotive college and had to work on a diff, still couldn't work out the point, or physics. Eventually I got my second radio controlled car which was rear wheel drive, but had a diff, the first one had a fixed axle. Setting it up on the table, and for the first time I finally understood that until you see one working correctly, e.g. the drive going into the crown gear, and then comming out of the two axles, it will never make sense.

Suzs bought me a Lego 4x4 with tracks, and that has 3 diffs. Not realising it would matter, I put the front one in the wrong way round. It took me ages to work out why the rear wheels were going forward, but the front were going backwards. Even finally understanding how a diff worked, I had not realised they had a right and wrong way round.


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[Davey Boy]

Originally Posted by Jay666d

My favorite diff video on YouTube: https://youtu.be/yYAw79386WI

Agreed Jay
A masterclass and a lab technicians dream!

D

[Lazy-Ferret]

Originally Posted by Davey Boy

Agreed Jay

A masterclass and a lab technicians dream!



D

Thats a great video, but like all, it takes a leap of faith when it goes from explaing the diff, to how you get the drive into the diff.

Can you imagine health and safety on that last bit today?

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[Wallace]

Originally Posted by Jay666d

My favorite diff video on YouTube: https://youtu.be/yYAw79386WI

Great video, those display models must have taken hours and hours to make as all the brackets and fixtures were beautifully finished.

Jim, just to mess with your head a little more, here's an exploded view of the Quaife ATB!

[solarman216]

The concept there it seems to me is that in the event one wheel loses traction the gearing is such that it will try and spin much faster than normal and via the inherent resistance in the small gearing impart some drive to the good wheel, could be quite noisy thou I reckon, Rick

[Wallace]

Originally Posted by solarman216

The concept there it seems to me is that in the event one wheel loses traction the gearing is such that it will try and spin much faster than normal and via the inherent resistance in the small gearing impart some drive to the good wheel, could be quite noisy thou I reckon, Rick

A friend has one in his VW Polo, it acts like an open diff at low speed and doesn't affect the handling like a tight plate diff. It is quiet and made a huge difference to the traction. If we ever get back into the V8 Manta project that will be getting one for sure.