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Another fact that i noticed was that on some models if the diff lock lever was between the gates as in not in normal and not in diff lock.....you would have no drive at all
Front prop shaft failure is common when the centre diff does not always release. If no front prop is connected and the centre diff lock is not engaged you should as you say just spin the front flange.
We run a fleet of Defenders which are the same setup as the Disco, its quite common for the diff warning light to be going on and off but for the diff to stay locked. This can be the only way your Disco is moving. Thats unless the centre diff is knackered in some way which may explain the collapsed front prop.
Just read your other post. It shouldn't be possible to loose drive when selecting or deselecting diff lock but it is possible to loose drive if you are in the middle of selecting high and low gears. As this is on the same lever as the diff lock I suspect the transfer box selector may be playing up.
cant remember exactly as it was about 5 years ago..........there may be a fault in the transfer box but im not about to start looking at it ...after all i got out of working on those things a few years ago
my statement about torque wind up still stands though........if the diff lock is still engaged on tarmac it will damage the transmittion somewhere along the line.Balfour Beatty used to destroy so many props it was ridiculous
like i say all my experiance is built up on the older vehicles....mainly M.O.D vehicles as they used to have 4 a week through our workshop with box faults
thats also a possibility.......it was about 3 years ago i last worked on them so i cant remember everyting i learnt about them....its just the bits that stick in your mind when you get odd faults and you cant quite remember the full details but know roughly what it was/wasnt doing
The basic transmission is the same as for the first Disco,Defender and early Range Rovers. The differnce on the New Discovery is that they have added (Depending on model or options) various electronic traction control devices. Just like on road car systems the Land Rover sytem applies the brake to any wheel that is spinning away he torque, thus transfering torque to wheels with traction as an addition you can also have the Hill decent system on the new Disco as well.
What i need to do next time i get hold of one is jack it up on the front and see what happens.....i will try to get a few of each age range........actually i think there are a couple of M.O.D spec Landrovers in one of the units from about 95 i think.....we dont get so many series 1 and 2 wrecks coming through anymore but i will try.......i want to do this now to satisfy my own mind and remind me exactly what i found out years ago and to see if im balking tollocks
The vast majority of the problems we have with our Land Rovers is that they are driven by people with no training or knowledge.
By far the biggest single problem is damaged transmissions by people leaving diff lock engaged. As you say the system gets wound up. Only way is to reverse or spin two side wheels on wet grass or something.
Best way for anyone to think of it. Imagine your car going on a full lock turn, the fronts travel a lot futher than the rears so the front wheels rotate more than the rears. With diff lock engaded the front and rear wheels have to turn at the same rate, if you are turning on a high traction surface you are going to put the entire drivetrain under extreme stress, if the wheels dont spin and crab you will smash the the weekest link in the transmission (Usualy diff or prop)
i may be contradicting myself and other people as well due to my experience being mainly on Ministry of Defence spec Landrovers (which are not the same as normal road going variants........you cant get parts for them from the dealers due to being made specially for the MOD for some odd reason)......some being stupidly old with gearboxes which look identical to a lot of the newer stuff......which may have me confused......
If i am wrong then i appologise.......my fault for not looking into it further.......
Apparently Land Rover went down the electronic route rather than just a viscous diff set up as it worked better at very low speeds, don't have to have wheels spinning at different rates for it to work.
Its all part of the low speed ABS/Traction Control/Hill Decent package that Land Rover developed and BMW pinched.
The MOD "light weight" spec Land Rover actualy weighs more than the standard Land Rover. It just has easily removed panels that, when removed, make it light enough to be slung under the standard army helicopter thingy.
I think with the exception of Wolf vehicles whose axles have a re inforced casing, all military vehicles have the same transmission components as civilian vehicles, ie, hardly had any development since the early 1950's.
Permament 4wd Land Rovers
Series I 80inch, 1948-1950ish
All Range Rover
All Discovery
All 90/110/130
FC101
Series III Stage 1 V8
Part time 4wd
Series I, 86,88,107,109 inch etc
Series II,IIa,IIb,III
All Lightweights
Each Series had a few 4x2 only variants, not civilian, most being used by the RAF.
Fantastic thread people, wish I'd seen it earlier.
In order to give car-like manoeuvrability and driving feel, most of the drive is channelled to the front wheels in a normal tarmac straight-line mode.
If the vehicle is operating in slippy conditions and one of the front wheels starts to lose traction, the difference between the front and rear propshaft speeds is sensed by the Viscous Coupling. The instant this happens, drive is progressively split as required between front and rear axles to maintain forward motion.
How it works.
The Freelander 1.8 petrol is fitted with the conventional 5-speed PG1 gearbox. The Freelander does not have a separate transfer box splitting the power from front to rear.
Instead, it has an Intermediate Reduction Drive unit bolted onto the gearbox where the Final Drive unit is located. This reduces the ratios by a factor of 1.458 to give relatively lower gearing, and also rotates the drive through 90 degrees to the rear axle, via the Viscous Coupling. This gives the benefits of lighter weight and reduced transmission noise.
The Intermediate Reduction Drive
The IRD incorporates a differential assembly, a primary and secondary helical spur gear train, and a hypoid gear set. It replaces the traditional transfer unit and performs 3 main tasks:
Reduces the gear ratios of the manual gearbox by 1.458 to the front wheels via the helical spur gear train.
Rotates the drive through 90 degrees to drive the propshaft and rear wheels via the hypoid gear set.
In conjunction with the Viscous Coupling, gives the vehicle an automatically activated four wheel drive system without any extra levers.
The IRD is driven from the manual gearbox Final Drive carrier. Depending on the slip at the front wheels, power is transmitted to the rear axle with torque split front/rear to suit the prevailing driving conditions
Discovery is absolutely 100% guaranteed permanent four wheel drive, with high low transfer box. The second small gear selector allows you to move between high and low range but always remaining in four wheel drive, and when in low range to also lock the centre differential.
The diff should only be locked when on a slippery surface never on tarmac to avoid damage, though you can if you are feeling perverse you can run around in low ratio on the tarmac with the diffs unlocked, just its not particularly useful having a top speed of 35mph maxed out in fifth gear.
And to add to dteagles reply even then LR won't admit its not permanent four wheel drive on the Freelander. On normal nice dry tarmac the power going to the front wheels is 100%, just they don't want to admit to having a part-time set up exactly like the Honda CRV which came out at the same time, as they thought it a unique selling point to say they had permanent 4 wheel drive.
The four wheel drive systems of the Freelander and the CRV are of a similar type, with a front transverse mounted engine driving the front wheels with the rear wheels connected via viscous coupling.
The Freelander 4wd I'm afraid to say operates just like every other similar car of this type, CRV, Cavalier, Golf, TT with the drive only being directed to the rear wheels when the front wheels begin to slip. The transmission is too inefficient to operate as permanent 4wd with the drive from a tranverse mounted engine being turned through 90 degrees to supply power to the rear wheels. Landrover have never admitted it publicly, but in internal documents which were leaked a few years back by a manager who had the hump with the Rover management at the time of BMW group still being in control, it contained confirmation of this, plus the 150+ known faults with the Freelander at the time of launch. Glass popping out, misted up rear windows, flexing chassis, gearbox faults........
I paid particular attention to this at the time of launch as I was selling the CRV at the time, thus finding out this little nugget of information was priceless to borrow a phrase. This was all printed in Car magazine a few years back, needless to say I kept that particular edition in my desk drawer at the showroom.
All other LR's have permanent 4wd to my knowledge, but not the Freelander I'm afraid. You could describe it as permanent 4wd if you wanted and as LR choose too, seeing as strictly speaking it be will powering all 4 wheels as an when necessary without having to switch modes. But seeing as everyone else calls this a part-time 4wd system it does seem to be stretching the truth.
The transmission is too inefficient to operate as permanent 4wd with the drive from a tranverse mounted engine being turned through 90 degrees to supply power to the rear wheels.
Interesting point. Is this specific to the applications mentioned?
I'm asking this because the Toyota RAV4 (front wheel drive version excepted) have a transverse engine with full time 4wd and a 50/50 torque split. Old models had a free "centre" diff with diff lock, new ones have a viscous coupling.
Presumably the Toyota system is more efficient.
D
Edited to add, it might be getting somewhat pedantic, but there is a difference between 4 driven wheels and how much torque is applied to each axle. Surely "permanent" suggests the drive cannot be disengaged as in the selectable 2/4wd of the Shoguns, Troopers, and the like.
if you lift a freelander into axle stands, start it up and engage a gear all 4 wheels will turn.
Would that be because it has an open centre diff?
You cannot do this on a scoob as it has the viscous coupling centre diff. AFAIK
I stand to be corrected.
As Andy says an open differential allows total slippage between driven wheels whether its front to back or side to side. In theory if all four wheels were turning at the same speed with the same traction the power would be distibuted evenly between the wheels. An open diff allows near equal torque to be transmitted to all the wheels.
When you lifted the rear wheels off the floor they were allowed to spin away all the torque so the front wheels had none. If you had lifted the front wheels the fronts would have spun and the rears wouldn't move.
You can get "Cross Axled" in a Landy, this is due to when total diagonal suspension travel is reached and one front wheel and one rear wheel is lifted off the floor. In this situation, even with centre diff lock engaged, one front wheel and one rear wheel will spin and you will go no were. This doesn't make the Land Rover two wheel drive. Serious competition off roading Land Rovers have locking diffs in the rear axle as well to prevent this happening.
The early Land Rovers, Series 1, 2, 2A and 3 (pre 1982ish)had the centre dog gear system and were only rear wheel drive in most circumstances. Although the front wheels were not driven they were turning which meant the axles and diffs etc were turning adding to fuel consumption and wear. To prevent this owners fitted "Free wheel hubs" which allow the front wheels to be disonnected from the front Axle. The downside to FWHubs of this type is that you have to get out and engage them if you wanted 4X4.
Owned three Vintage Land Rovers, one Disco, drive a Defender 110 for my work get around, subscribe to Land Rover Owner magazine and I'm a member of the Land Rover Owners Club.
Echo Andy's comment, was never my intention to cause any offence.
Open (Normal) diffs do allow either side of that diff to spin away all the torque if there is no traction. The motor industry classes an open diff as a unit that transmits power to either side of that unit, so something like a Mondeo 1.8LX is classed as being two wheel drive. Off roaders that have a centre diff for front/rear split as well as the usual left/right split are classed as four wheel drive(Although loose traction on one wheel and your stuck). Sytems that allow a set of wheels to be disconnected from the drivetrain are said to not have permanent four wheel drive.
Judge for youself if the industries descriptions fit your own expectations.
applies the brake to any wheel that is spinning away the torque
That means to me that.........
instead of fitting an LSD they use the ABS to do the work meaning they dont have to redisgn the diffs to accept a viscous coupling.....just a few more lines of code in the ABS ECU
=dazc2;1718837]The Land Rover Disco is not permenant 4x4......it is switchable rear wheel drive and 4 wheel drive hi and low ranges.........it hasnt got the viscous couplings of the Range Rover and cant tolerate being on tarmac unless its in 2wd setting, if you run a Disco in 4x4 on the tarmac you will suffer torque wind back and will snap half shafts in the axles or rip the splines out of the diff..........this was true for anything older than the new shape which may still be the same transfer box as i know very little about the recent face lifted versions.[/QUOTE] The Disco is so full time 4wd always had been. Lock the diff in and drive on sealed roads and you will wind the diff and make a mess of your running gear. Other wise front diff and rear diff drive independently.
LOL, most Disco series II are on the scrap heap now...My mate's just had to condem his for the ol' heap in the sky...usual MOT fail for these...big hole in the rear chassis leg.
Wish he told me first, as I wanted the engine for my S2A (Td5 lump would work a treat in that).
Let me clear it for all out there.
In the case of Defender is a 2wd permanent Hi can be engaged without the diff lock no problem. Only the rear prop shaft is pushing the car forwards. When you engage offroad diff locks ( HI-LO ) then it becomes a four-wheel drive, that is if you have traction on all four wheels. If you want a true offroad while with a HI-LO with the central diff lock you should get a separate rear and front diff locks to split the power 25% ratio on all wheels. If you don't get it you are not understanding.
I cant believe im spending time on this ....... but the defender started at A reg and had 3 diffs 1 front 1centre 1 rear the front and rear remained open at all times (unless modified) the centre could be locked in either hi or low range if you lock that diff on road you wind up the centre diff .
the defender up the 300tdi /200tdi was more or less the same but for the introduction of a different 5 speed gear box they were all permanent 4 wheel drive but the power always went to wheel with least grip unless you install front and rear diff lockers such as the Detroit
Heres my old one.
Edit ; some of the very early ones may have had front free wheeling hubs .
Last edited by lockheed; 23 November 2020 at 06:11 PM.
Reason: accuracy
08 January 2003, 09:56 PM
