Hi Niki, not sure I quite understand the question. Firstly is it an auto or a manual?
Getting either into reverse would be very hard whilst going forward. On a manual, I'd say almost impossible UNLESS you put it into reverse whist not moving, rolled forward and then let the clutch up. That would be terrible. But you couldn't do it whilst moving.
On the auto, you'd have to press in the button on the shift lever. I don't think that it would let you get it into reverse, but I have never tried it. So we need an auto savvy person to answer this one. Jon - any wisdom?
As to your question about normal drive and H, well H is normal drive. Did you mean H and then HL? H is normal and then HL is normal with the middle diff lock engaged. Getting it into reverse whilst moving wouldn't really be any different in either case, as outlined above. BUT if you placed extra load on the drive train, then being in HL could have significant differences depending on what the vehicle was doing at the time. It allows less 'slippage' for the axles etc and does place extra strain on the components. Normally when you drive you are going forwards. OK, when you accelerate you get pushed backwards, yes? This is about 'weight transfer'. Well this usually means that the front wheels effectively feel lighter and they can spin. When you brake, you get the opposite. What we need to understand is the combination of what happened and under what forces the drive train was placed. Going forwards, then getting into reverse would be a catastrophic combination.
All academic though I suppose as it's broken and that's that. But as I said previously, you are very very very unlikely to get a bad front diff from a scrap 90 to go on yours.
Crispin, just read that about wind up. The answer is always, well it might have, but the weak point is the half shaft, not the drive really. And if one wheel can spin, all the spare energy goes out that way. The only way a front can't spin is if it is under extreme load and grip such as braking. Or going backwards. LCs are not prone to wind up. Why, because they are beautifully designed and made. There has been lots of talk about wind up and most is piffle in my view. Huge problem on sloppy badly made, 4x4 systems without proper centre transfer boxes. But on LC's? Not really. Of course there are degrees of wind up, but not the sort where you have to jack a wheel up off the ground to get it released.
Lockers not engaging etc it's wind up, it's mild misalignment.
Chris