Can someone please enlighten me please? I have always heard that it's such a no-no to put different sized tyres on front to rear axles, or that you should always change axle tyres in pairs, all to avoid this so called diff wind up. Now I might be being stupid, but isn't the whole point of a diff to allow for differences in rotational speed across axles and (in the case of 4x4) front to rear axles? So, what the heck is diff wind up? We aren't talking lsd's here, just standard diffs. Would they overheat in normal use with minor differences in output shaft speed, is that it? If so, why don't they overheat on normal twisty roads? Drives:
2010 FFRR TdV8 Vogue - Stornoway Grey
2010 FFRR TdV8 Vogue SE - Zermatt Silver
1998 BMW E36 M3 GTII

I think diff wind up applies to the older systems, whereas ours tend to be more open diffed, with traction control taking up the slack.... May be wrong. I know some early Defenders (not really Defenders, the Series ones) and like mk1 Shoguns have the issue in 4wd, which is why it's not recommended for on road use.

With tyres with different circumferences, due to wear, I'm not sure if it may confuse traction control, though the speed difference would need to be big for it to cut in. As for the centre diff, I'm not sure..... 2011 Range Rover Vogue SE 4.4 TDV8

Previous cars :
2003 Range Rover Vogue TD6
1999 Discovery Td5 ES
1995 BMW M5 3.8 6 speed
1992 Range Rover 3.9 Efi Vogue
1992 BMW M5 3.8
1988 BMW 735i SE
1989 Ford Sierra XR4x4 2.9i
1981 Ford Fiesta Supersport

you don't have diff lock

Diff wind up happens on locked diffs, when one output side cannot rotate at a different speed to the other on a high grip surface the diff will 'wind up' and can lead to broken half shafts, diffs etc. It's the equivalent of having a solid steel bar and trying to twist one end more than the other, something will eventually break. It's why you don't use locked diffs on tarmac roads.
It's not an issue on loose surfaces as the lower grip means the wheels can rotate more freely.
The same applies to the centre diff on an AWD vehicle.

Having wheels and tyres of different sizes on the same axle does mean an open diff will be working all the time. It can lead to overheating and premature failure also it won't help the likes of ABS systems and traction control. It's nothing to do with diff wind up.

It reminds me of a story told to me by an ex-army guy who used to drive Alvis Stalwarts in German. They were 6 wheel drive with no differentials, they just used a bevel gear system so were permanent 6 wheel drive. Fine on the loose stuff but a nightmare if you were driving on tarmac autobahns! The centre of the axles were painted with a line, if the lines weren't all in the same direction then it was getting into a diff wind up situation (or rather axle wind up) and to release it they used to simply bump into kerbs. The action of bumping the wheel on the kerb hopefully caused it to knock it up off the ground and released the wound up torque difference.