From previous posts you'll know I agree with Huw, he keeps pointing out this rock crawling business but doesn't point out the reason the diff lock is essential here, it's because the axle articulation does not cause all wheels to fully share the weight, one wheel can find itself effectively hanging in air. Also there then tends to be a very high torque requirement on the remaining driven wheels to lift the vehicle over the step. Traction control via brakes has a problem here as it is both power consuming and causes high torque variations in the drive train, because to absorb one wheel being braked the opposite wheel has to double in speed or something give in the drive train, instantaneously. Unfortunately I have never had the experience of using either traction control nor hill descent control. AJH
I've seldom, if ever, found this to be a problem with LR suspension on any 'track'. While I agree with most of AJH's post, the main difference between a steep ascent where traction control works superbly and a 'rock crawl' is the speed at which the wheels turn. They turn so slowly while rock crawling that the traction control just isn't effective, possibly because the signals are not sensitive enough to the difference in wheel speeds at such low speeds. I tend to find traction control rather crude in this condition. Otherwise it is an energy intensive and stressful business is traction control.
I also find HDC an extremely crude device which I prefer not to use if I can help it because it is more likely to break traction in extremis than to safeguard it. Before I take my new RR on the banks this Spring I shall need to find out whether it has a viscous centre diff or whether I shall have to switch the HDC [yuk!] on for best safety. Anyone know what the new RR has? Viscous, electronic, Torsen or just open?
AIUI it's part of the terrain control system or whatever they call it. Perhaps there's a LR expert who can tell us on which terrain type it is switched in.
Priority of both groups is the same - to keep moving.
Well I had a 90 for a number of years equipped with front and rear axle diff locks used for green laning and fun sites where you meet the more extreme conditions. Time and again people would come up to me and say how easy I made it look after they had struggled to make progress. Being a modest sort of chap I had to explain that it wasn't my superior driving skill, just the fact that I'd put the axle diff locks in.
I was also the one most called on for the really stuck recoveries. I agree diff locks are crude in comparison to the technology involved in Traction Control and yes if I was buying a new vehicle for every day use then I would go for traction control rather than axle diff locks. But really the difference between an axle diff lock and a centre diff lock isn't that great in terms of getting traction, namely preventing all the torque disappearing into a spinning wheel. Surely if they can be effective on tractors then in principle they will work on any 4x4.
.... I must be not remembering it right then. I thought the front had the spinning weights to change up as the revs got high and the vac operated bellows to change down so it had enough engine breaking to feel OK and the rear was just cones and springs to take up the slack.
I still don't remember a low ration button. I think I've still got the Haynes manual somewhere. I'd better look and see...
I blame forgetting things on all those beefburgurs I ate in the 80s.
The rear axle locking diff is not standard fit on the new Disco
One has cost effectiveness and usefulness as higher priority. Virtually no farmers will piss around fitting axle diff locks to their Defenders because they know it won't get them much more than a few inches further and probably won't get them back from there.
And no doubt you had extreme tyres on as well. Great. Farmers and other business users do not piss about like that and have tractors and such for, what you call, extreme conditions which they try and avoid like the plague so as not to poach the land more than neccessary.
Yes they will but the use of a diff lock presumes that there is traction for it to work. A heavy draught tractor pulls many tons of draught in conditions which, as a rule, vary considerably from one side, the land side, to the furrow side. They have deep lug, self cleaning traction tyres and their primary purpose is to pull loads. The LR OTOH is likely to pull on greasy surfaces which do not offer much traction and which is likely to provide near enough equal traction to both sides. Now you will say that the axle diff locks provide an advantage in competition. Sure, mainly because of the twisters purposley built in the course. But in everyday use, even serious use, they are of no use. My LR is used off road almost every day all year and I have never felt the need for axle locks. The LCruiser has them and I sometimes lock the back [and *very* occassionally the front] only to find the LR whiz past where I come to a stop. That is mostly down to the tyres of course but does show that tyres are far and away more important than axle locks.
I just blame it on senility. The front pulleys were controlled by engine vac, the rears by centrifugal force according to wheel spin, moved apart so pulley diameter was reduced as speed built up, i.e. gearing got higher. The whole thing was then mounted on a sled with springs to keep the belts in tension. Long time ago so I may be wrong.
The clutch was also centrifugal, in two stages. Amazing that it ever worked.
I actually had nothing more extreme than BFG MTs. But yes, I agree with you again, tyres are the most important single factor in off road traction, and if you are basing your assessment on the effectiveness of diff locks on a vehicle with normal road tyres then I'm not entirely surprised that you are less than enthusiastic about them.
But generally 4 wheel drive is better than 2 wheel drive is better than
1 wheel drive or to put it another way, 3 diffs locked is better than 1 diff locked is better than no diffs locked. Whether it is cost effective or value for money is a matter of personal preference, like most things in life.
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