Does anyone know the width of a R31 diff that has been shortened and the short axle then used on the long side?

Cheers

Depends how much you shorten the long one by. We normally aim for 1305mm disc to disc (std 1200 width). That said, there is a some scope to vary either side of this figure.

1200s are 1330 drum to drum, 155mm narrower than an r31 diff

50mm off one side of the housing, 105mm off the other and 155mm off the long axle...if i remember correctly

1200 Drum to drum is 1305mm
R31 Disc to Disc is 1460mm
My current diff 1355 Drum to Drum

Looking at R31 diff if you use short axle on long side you need to shorten that side of the diff by 50mm as the axles are 50mm different in length. Then by shortening the other side of the housing by 105mm you achieve a new diff width of 1305mm the same as 1200. Then re-spline long axle to suit.

I assume that the tail shaft would be slightly off center???

So in my case where I want 1355mm disc to disc. I use short axle on long side and need to shorten that side of the diff by 50mm as the axles are 50mm different in length. Then by shortening the other side of the housing by 55mm I would achieve a new diff width of 1355mm the same as current setup. This would require the long axle to be re-splined just below where current spline is, as it is only shortened by 105mm. And this is close to the thin part of the axle I would probally need to get one axle machined from a blank.

Also the input from the tailshaft would onlybe approx 10mm off center.

So does this all make sense?

are they really 1305mm...could swear all the ones ive measured were around 1330, interesting. maybe im just remembering it wrong

yeah your right, will probably have to get a billet axle to only shorten it by that little

shortening the r31 diff to stock 1200 width makes the pinion only a tiny bit off centre, but puts the bulk of the housing a fair way off centre. as the pinion is off centre in the stock arrangement

so if you are shortening one side 50mm and the other 55mm then the pinion will be 2.5mm closer to the centre line of the diff than it was at stock width