Black Magic Diffs

jims-terrano · 08-02-2020, 03:21

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 · 08-02-2020, 03:36

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 · 08-02-2020, 08:51

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 · 08-02-2020, 12:51

Quote:

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 · 08-02-2020, 16:41

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

jims-terrano · 08-02-2020, 17:31

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

Davey Boy · 08-02-2020, 19:27

Quote:

Originally Posted by Jay666d

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

Agreed Jay
A masterclass and a lab technicians dream!

D

Wallace · 09-02-2020, 10:35

Quote:

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!

Lazy-Ferret · 08-02-2020, 19:03

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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08-02-2020, 03:21	#1
jims-terrano Senior Member Join Date: Sep 2004 Location: UK Posts: 12,965	Black Magic Diffs 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.

08-02-2020, 03:36	#2
solarman216 Off road maniac Join Date: Dec 2009 Location: Bexhill on Sea Vehicle: Y60 Patrol Me, 3 ltr Mrs Posts: 17,430	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 __________________ Ex banger racer now off road maniac Lokka on the front with manual hubs Diff lock on rear 3 inch SS straight through exhaust Manly winch bumper with 13000 lb winch 10 spike ground anchor, with multiple straps and blocks Super strong body cills capped with scaffold pole 20% stronger springs all round aggressive off road tyres on wheels so just swap. Aim to get stuck and be completely self sufficient in extraction, love getting muddy, 2ft deep is good but rare.

08-02-2020, 08:51	#3
jims-terrano Senior Member Join Date: Sep 2004 Location: UK Posts: 12,965	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.

08-02-2020, 16:41	#5
Jay666d Senior Member Join Date: Jul 2016 Location: Northumberland Vehicle: Patrol GU3 (Y61) 3.0 SVE Posts: 1,375	My favorite diff video on YouTube: https://youtu.be/yYAw79386WI

08-02-2020, 17:31	#6
jims-terrano Senior Member Join Date: Sep 2004 Location: UK Posts: 12,965	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

08-02-2020, 19:03	#9
Lazy-Ferret Senior Member Join Date: Jun 2012 Location: Sevenoaks, Kent Vehicle: Terrano 2.7TDi SE Touring Posts: 5,221	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. Sent from my SM-G930F using Tapatalk