new 6-wheeler disco plan

You do have the problem of driving the two rear axles off one transfer box output while driving the front off the other, the diff will split torque both ways but you've got half the torque going to the front and half going to two axles at the rear so each rear gets half the torque the front would get. Whether that's a real problem or not I'm not sure given that you can lock the diff if the front starts spinning.

On the pinz 6x6, drive from the middle axle is carried straight through to the rear axle with no diff between axles (in fact there's no diffs between any axles), at the rear the transmission wind-up isn't significant as they're close to each other, but then again it was a system designed with that in mind, so while there will be some stresses the drivetrain's designed to take it. When you corner hard, it has to drag tyres sideways anyway so there's ample opportunity for the drivetrain to unwind.

Best bet though is to try and have a look at how it's been done on some of the many 6x6 conversions already done and see if parts can be copied or bought. Not much point trying to solve an already solved problem ;-)

On or around Mon, 8 Feb 2010 13:29:33 +0000, Ian Rawlings enlightened us thusly:

I know the 8x8 thing used 2 standard transfer boxes, one driving axles 1 and

Good point about the torque, too: the sierra 4x4 had a clever T-box which split the torque 2/3:1/3 which would be neat. It does it by using an epicyclic gear set as a diff, and no, I wouldn't have though of that either, but it works.

The idea of no diff between the rear pair is a possibility, it shouldn't wind up too much as you say, since the axles are close together. In fact, on your Pinz and on normal 6-wheelers, the vehicle tends to pivot around the point between the axles (other things like effect of terrain exceluded) and that means it shouldn't really wind up at all... of course, my plan involves a counter-steering rear-most axle to eliminiate scrub and retain the original turning circle (and yes, it will work, see the things with 8x8 setups where the 2 opposite ends steer opposite ways) so I guess it could wind up a bit.

Mind you, disco II has traction control, which should dump torque back to the rear end if the front slips, and that ought to work OK provided there isn't a diff between the 2 rear ones.

On or around Mon, 8 Feb 2010 22:42:31 -0000, "Roberts" enlightened us thusly:

Those walking beam things on the old Scammels are not ideal, they have a huge amount of unsprung weight and from what I heard from someone who's driven one, large amounts of lash in the transmission. Since the thing was mainly a tank-recovery unit it's really just a big tractor, so that doesn;t matter too much.

The thru-diff idea is good, except that it means a rather heavily modified axle casing and, to get it right, some fairly hefty tooling: remember the disco is capable of 100mph speeds, so it needs to be right, not just nearly right.