Snagger

Not surprising that you have concerns with that experience John, but a lot of people seem happy with their Insas and Colway had a good reputation (I think they're gone now, though). I haven't used remoulds on my LRs, though the Chavalier I bought to use while I rebuilt the 109 may have had some - whatever it had, they were cheap Ploppy Plop Plops (Road Champ, I think); they were as slippery as hell. That said, some of the new premium brand tyres I have used have been poor too, and I have only been satisfied by the BFGs so far. There are a lot of variables in tyres, more than just the question of new vs remould. Fr what it's worth, most aircraft tyres are remoulds, and given the forces they're subjected to (inflated to 220psi, spinning up to 170mph on touch-down with a typical weight of 15 tones per tyre), they rarely let go without severe provocation.

To be honest, I really don't know if running different sized tyres front and rear long term would cause a failure, but I can't imagine the centre diff would not wear a little faster and if the size difference was big, then I suspect damage could occur after a while - the system is designed to have matched tyres with the diffs operating just when cornering, and the rate of differential operation under normal conditions would be low. Even on very tight turns, the forces would be minimal because the speed is low, though the difference in front and rear wheel revolutions will be at its peak. So, though I don't see a problem using mildly mismatched spare or front/rear tyres for a short time at lowered speeds, it's not something I'd recommend long term.

Fantastic! Thanks, Bowie!

The Roverdrive, now known as the Roamerdrive because of LR's overzealous legal department, it pretty robust - a lot more so than the Fairey. The innards of the Series and Defender models are mostly the same, I believe, with just the front sections and torque couplings differing. Now, if Ray was to introduce an oil cooler port in the back of the main casing that would allow cooled oil to be pumped at a low rate directly into the rear bearing, which it the one furthest from the existing oil supply, then I think this would make the unit nearly indestructible. The port could be simply plugged for base models with an accessory cooler kit for users of heavy vehicles or in hot climates.

Unfortunately, my Rave discs got lost in the house move!

John, you can't say all remoulds are rubbish on the basis of one set - there are many different brands, compounds and treads. It's like saying all cars are rubbish because you tried a Micra...

The rattling sound seems to be getting more noticeable when the vehicle has done 10 miles or so and everything is warmed up, though is still fine when cold. I jacked a rear wheel up and turned it over by hand (hand brake off and transfer box in neutral) and found a clonk every second turn of the wheel, or every turn of the diff. The sound is definitely coming from the rear diff housing. A quick call to Aschrofts for some advice (thanks, Dave) suggests a damaged crown wheel with either a crack or a high spot. Since we have only owned the vehicle 9 months and LR Approved Warranty is 12 months long, it should be covered, saving me a job and few quid. I wonder how hard I'll have to press them, though...

Ah, that's interesting! I had thought the washer jet heating was simply wired into the rear screen circuit, but this is quite plausible. It's a shame the Haynes manual doesn't cover the late models well.

Unless you have broken yours, then don't bother replacing it - it's just hollow plastic. Clean it out with petrol. The hoses may need replacing, but not the plastic unit.

How about high torque electric motors on each diff and a turbine powered generator? Independent drive on each wheel, so no transmission at all, miminal power loss and extreme torque at low speed with very high rpm available... Now that's the future!

I have just found a black circular sensor fitted immediately inboard and above the driver's side headlight on the steel panel that supports the headlight cage. It looks very much like a reversing sensor, but a little smaller. There are unused drillings for the same sensor on the passenger side. The sensor is hidden by the solid area of the plastic rad grille when in place, and has just two wires that feed into the wiring harness along the rhs wing. Does anyone know what it is? It can't be a light sensor because of the grill panel obscuring it. A temperature sensor, perhaps, but for what - my RRC is a simple 300Tdi, so has no engine or HEVAC ECUs?

Heat and noise are energy that has come form the engine, so are a sign of inefficiency. Unfortunately, even in 4th and driving straight through the box, the lay shaft and main shaft gears will still all be spinning as they are in constant mesh, and the free-running main shaft gears will all be turning at different speeds on their bushes, so there is always some energy loss through friction, mesh generated noise and oil stirring. However, the energy loss will still be least in whichever gear gives straight-through drive. And yes, the more gear trains you have, the more the losses. However, efficiency can be gained by having an extra set to raise the gearing if the engine has sufficient torque to pull it in the peak rev range, such as with an overdrive.

I saw LRSeries advertising 4.1 diff crown and pinion sets for later diffs at about LRS' stock, though. Alternatively, finding a set of s/h 10 spline shafts should be cheap and easy, as would a pair of SIII diffs, ad with those diffs and shafts being the weak link in the transmission, you'd never have to worry about blowing the gear box. Either is viable, though rebuilding the 24 spline diffs as 4.1s would be a better technical solution and could be combined with locking diffs.

Some like it, but I think contrasting roofs in black look dreadful - that LR now do it is no indication of good taste! The only contrasting roof colour that looks any good to many is white (including off white if need be). White is also more practical as it keeps the interior cooler in summer and doesn't show water marks after washing. I'd get a can of matched aerosol paint from an autopaints specialist or body shop (most towns have them) for the hinges (think how awful the hinges looked on the Heritage specials) and just paint the sills satin or matt black. Stone chip would be a good idea for them, but be warned it isn't water proof, so you'd need to kill the rust and prime the sills first.

How was the show, Mike? Any goodies?

You'd be better off with the 1.4 transfer box, which will take an overdrive, and lower ratio diffs like 4.1 or even 4.74. Especially easy if your Disco is old enough to take a pair of diffs straight out of a SII/SIII (ie 10 spline diffs). The lower diffs will take some of the strain out of the gear box and od. They'd also reduce the ratio in low range as well as in high, which would help with the effects of the tyres.

Mine either, but for something that ugly, it flies pretty well! Here's another video that shows what these things are used for. I can't imagine how low brow the audience are, but their cheering the crashes more than the successes gives a good indication. ANyway, it's still pretty impressive what abuse the vehicles seem to stand up to: http://www.youtube.com/watch?v=WwjGo3kQgMw&feature=player_embedded

Just out of curiosity, Bill, how old are you? I'm only 40, and if it's any consolation, feel much how you describe already - I find it hard to drum up the enthusiasm to go into the garage to work on my RRC, but then I am continuously putting in the legal maximums at work (not my choice). What tyres do you use on your RR? If they're oversize, then the vapourdrive would need to be a crawler for your use. Mine gets plenty of road use (or did), and very little off road, and even though it only has a standard 300Tdi turning the R380 and BW unit, I often wish for a six "cruising" gear on motorways. I might fit slightly oversize 235/75s when it's finished just because of that.

My post probably was unclear. Using a bottom PTO configuration for an overdrive would require additional new input and intermediate gears to take those tow out of mesh, and would also be tight on space laterally as the OD input and output would have to be side by side, the drive line dropping down from the gear box main shaft to the OD input shaft and then to the right to its second shaft before being routed back up to the intermediate cluster. One of those shafts would need sliding members to lock and disengage the 1-1 and step up gears, and even in 1-1 you'd be running the torque through gear sets rather than locked shafts, so loosing efficiency. It'd be much more complex and less reliable and efficient than the existing designs that use the rear PTO position.

I agree that it's the heat that is the problem on both types of unit, and that the bearings on the Fairey are pitifully small. Rather than coming up with a completely new design that achieves the same thing, creating a heat exchanger or oil cooler system would probably be more beneficial. Using the transfer box filler plug hole would be a good return line point, but then again tapping a line into the top of the case might be better so that the filler hole can still be used for level checking. The challenge would be in siting the hot oil outlet port. Maybe somewhere on the rhs of the transfer case would work? Cant't use the rear face because of the hand brake, or the front face because of the 4wd housing, and using the drain plug would be inviting disaster off road, getting ripped out on the first obstacle or in deep mud. But what about oil flow? What would work to pump the oil through the cooler? I don't know if an electric fuel pump would handle the heat and viscosity for long.

I still see no advantage - an epicyclic gear set with three planet gears will have six meshes - planet with sun and planet with ring, times three. A three lay-shaft system will also have six meshes - the front end of each lay shaft to the outer concentric output shaft and the rear end of each lay shaft to the inner main shaft. The thing is that a multi-lay shaft will be turning more mass of metal, but the radius of each piece is less. The ratios of mass/radius of all the turning parts will influence the amount of energy lost in turning all those parts, but I'd expect the epicyclic system would be more efficient and reliable as well as more compact for a given weight/strength. That's why they're used for aircraft propulsion gear boxes on turbine powered aircraft.

As long as you're sure the unions are all tight, the easy way is to open the bleed and spin the engine on the starter for a few seconds at a time, letting the starter cool 30s between each spin. After five spins, let the starter cool for five minutes, then have a few more goes. Once the engine fires, let it idle with a rag around the filter to catch the spillage while you let the bleed weep until clear of bubbles, then nip it up. If you can't get the engine to start after five cycles of five, then you have a more fundamental fuel feed problem. You might want to have a battery charger available before doing this.

You could, but it would be made more complex for it, also needing a new intermediate cluster as well as the main shaft gear (so that those two would no longer directly mesh) and complexity often means weaker.

I can't see much difference mechanically between elliptical gearing sets and a multiple lay shaft system - you have lots of bearing sets and teeth meshes sapping a similar amount of energy and generating heat, and in both cases opposing planet gears or lay shafts cancel out tangental loads on the sun gear or main shaft. One is more compact than the other, but I don't see any reason one should be stronger or more efficient than the other because they are doing exactly the same thing. As for Tanuki, I think I see the thrust of his point. The exact ratios he mentions are not hat point; what I see as the fundamental issue he raises is that the top gear selections should involve straight through drive, bypassing gear sets, so when the gear selection is giving you the least torque advantage by going high ratio, you are also minimising the gear set energy losses - it seems a shame to labour an engine with overdriving gear sets which are wasteful when straight though lock ups with higher ratio diffs would give the same end ratios far more efficiently. I hope that's what he was trying to illustrate - I don't want to put words in anyones' mouths. I think he's absolutely right - locking the gear box and a transfer box with a direct-locking 1:1 high ratio would mean the only gear sets to sap energy would be the diffs.

The thought of a doubled or trippled Fairey OD had occurred to me too (never as a physical project as I lack the skills and equipment to do it), but I came to the conclusion that the weakness of the clutch sleeve would still be there and that the heat generated by trippling the number of meshing teeth and spinning bearings would probably be similar to that of the heat generated in epicyclic gears, so you'd lose the compact design with no benefits. The better solution would seem to be a compact epicyclic design in a large housing with high oil capacity, ideally with an induced oil flow through/over heat shedding areas. The cooling fins on the Roverdrive must help to some extent, but are not huge and it's oil capacity could be made much bigger as there is plenty of room to expand the casing without altering the innards. The way in which the Roverdrive shares its oil with the transfer box, using a finned bottom cover must also help, but a pumped oil cooler would be even better. Maybe an electric fuel pump with a length of coiled copper brake line would be effective? Now, what would be a useful overdrive is one which would also function as an underdrive (ie, low, 1:1 and high) - I could really use that on my 109, giving huge flexibility for low speed and motorway work. I know someone was looking at it, but they shelved the idea because of the economy. Maybe if they considered how many more people could fit big tyres tot heir LRs, or cheap 3.54 diffs to Series vehicles but currently can't because they'd be overgeared, using the underdrive feature for town driving and accelerating and the high function like on current overdrives for long range cruising, so that people like me can have their cake and eat it, then there might be a market for such a unit.