The Schuler Super Ranger
ARTHUR Silverton is the General Manager ot the UK division of Schuler Presses, the German machine press manufacturers. He has been a Rover owner for over twenty-five years and had his first Range Rover in 1971. He started improving the vehicle shortly afterwards, as a private project, and decided that Ferguson Fommla transmission combined with an anti-skid braking system would suit the Range Rover particularly well. So, in conjunction with FF Developments Managing Director, Tony Rolt, well known for his racing exploits in the late thirties and immediate post-war years. a FF Range Rover was produced. Realising that others might be interested in such a vehicle, and wishing to take the development further than he could on his own, Arthur Silverton convinced Schuler on the viability of the project. Thus the UK division of the company found themselves diversifying into the four-wheel-drive market, with Arthur’s son Toby running this side of the business and that very experienced off-road event competitor, Alvin Smith, helping with vehicle testing and development.
A number of Super Rangers have been produced with varying specifications, for Schuler offer a full range of modifications for the Range Rover stretching from trim details, such as coach-lined paint finish, leather upholstery and Wilton carpets through to alterations like a four headlamp conversion, engine modifications, up-rated suspension, automatic or manual five-speed gearbox, FF transmission and Mullard electronic ann-lock braking: you name it, Schuler almost certainly do it — Range Rover-wise, that is. My first introduction to a Schuler converted vehicle was at a test track late in July, when the prime source of interest was the effect of the anti-skid braking system. The demonstrations were most impressive, with the converted vehicles stopping in a much shorter distance than the standard version on wet surfaces, with not a trace of wheel lock and with full steering control. We were also able to indulge in some steering tests and found that with the FF system fitted, the Range Rover handles and steers quite remarkably well. The secret of all this is in the transfer box, of which more later. We were not able to try the conversion out in off-road conditions (what I consider to be the natural habitat of the Range Rover — not Chelsea!) which seemed a pity as I was sure that the altered transmission (about which I had originally been quite sceptical) would really pay off in such circumstances. A word in Arthur Silverton’s car, and arrangements were made for me to borrow his own Super Ranger (something of a mobile test bed for the various developments) for a weekend to coincide with the VSCC’s Welsh Trial which I was helping to organise. I was not disappointed. Arthur’s own car has a standard engine and a Chrysler Torqueflite three-speed automatic gearbox combined with the FF transmission and Mullard anti-skid braking system. A cruise control has been fitted and the alloy road wheels were shod with Michelin M & S tyres. The trip down the M4 from Schuler’s HQ near Ascot was very relaxed, with the cruise control working perfectly and keeping a steady 70 m.p.h. It was immediately apparent that the chain driven transfer box, the heart of the conversion, was very much quieter than the standard gear driven arrangement, and the heavy cloak as the transkr is made from drive to over-run, which typifies the
standard version was completely absent. Luckily, I had no occasion to put the anti-skid braking system to the test, nor did I try any clever tricks with the improved steerability, despite the temptation of the near deserted roads between Hereford and Hay, for this waste be a test of the vehicle’s performance off the road.
The weather was ideal for this sort of trial — pouring with rain, as only the Welsh skies know bow. The way to the first sections was itself a challenge to competitors in such very wet conditions, being a path up the side of a field, with no proper base. The first section itself was very short, but extremely steep, something like I in 21/2, with a muddy surface over a loose stone base. The start line was at the foot of a bank, with the cars’ rear wheels in a small stream. In better conditions in previous years, I have seen Land Rovers sitting at the start of this section with a wheel spinning impotently in the mud. Thus my three passengers were more than somewhat surprised when, with the Super Ranger in low ratio, and the selector in the I position, I gently increased the revs enabling the torque converter to transfer power to the wheels very, very gradually — thus not breaking the limited grip between the tyres and the ground—and the laden vehicle muffled gently up the bank and on into the bracken. I am sure that a standard version would not have achieved this climb without a run at it, and I am equally sure that I would not have been able to coax a manual FF Range Rover up: my clutch control just would not have been good enough to feed the initial power to the wheels gently enough. After this, rock and bracken, shale and mud, grass and stream were all taken in our stride and! was beginning to think that the Super Ranger was invincible, but I was forgetting about Cwmheyope. Cwmheyope is the VSCC’s name for a very steep, mud on shale track running up into the woods on the north facing side of a hill. The approach is quite narrow, and there is a near 90° left-hander in a mud bath at the bottom of the section. In good years, when there has been little Autumn rain, I have seen Range Rovers with the odd competitor at the top of this hill: I have driven a locked differential Land Rover up in moderate conditions; but usually, only the bottom third of the hill succumbs to the modern four-wheel-drive vehicle. Some of the lightweight vintage cars manage it, just, but the majority flounder in the mud at the bottom. This year, there was more mud than usual. There was
more floundering than usual, and only one car managed to get its rear wheels out of the mud at the bottom. The Super Ranger would have got to the top, I am quite sure, if it had not been baulked by a carelessly placed tree trunk, blocking the track. What it would not do was to start off again once we had been stopped. I tried gentle power, and it moved an inch or two. I tried a higher gear and lots of revs, hoping to cut through the surface grease to the hard standing that I knew was below. I tried reversing down and starting off again, but this time, the tyre treads were all full of mud, the track surface was really slippery and we had to give it best. The following day was rather more pleasant, so it was something of a surprise to find myself running out of traction on a section which is not particularly steep. I attempted it a couple of times, and stuck in the same place on each occasion, despite trying different gear ratios and techniques. Thinking about this rather embarrassing failure (I had told a number of my friends how good the vehicle was,, I realised that it was the one situation, relatively common, where the clever FF system can be beaten. This happens when one side of the vehicle is higher than the other, and the two wheels on the upper side are on a more slippery surface than those on the lower. The two upper wheels lose grip together and spin at the same rates, the centre viscous coupling in the transfer box knows that the two peopshaltvai rotating at the same rate, and can do nothing to help. The fitting of a viscous coupling, or real, effective, beefy, limited slip cliff, to the rear aide would prevent this, and Schuler are already working on the possibility of such a modification. To summarise, I found the automatic FP transmission Range Rover to be very much more effective cross country than the already effective standard item (this is borne out by Alvin Smith’s outstanding competition successes with such vehicles) and! only found myself in trouble when both wheels on the same side of the vehicle log grip — a situation where a standard Range Rover would be equally badly off. It took quite a time to come to terms with the automatic gearbox se4-01, when coming down very steep, slipper,’ 400Pca at engine braking is almost non-existent at slog speeds whatever gear is selected and the anti-skid braking system is inoperative below about five m.p.h. (so that you can actually stop!). It can sIte he fooled into thinking that the vehicle has stopped if all four ‘wheels lock up together on a
greasy slope. Nonetheless, a little care and experience soon showed that there was no great disadvantage to an automatic, while there was much benefit in terms of smoothness.
As metioned before, the heart of this conversion is in the transfer box: this is where the drive from the gearbox output shaft is transferred and split to the two prop-shafts. On the standard Range Rover this transfer is achieved by a gear train and a conventional differential which will accommodate any amount of speed difference between the front and rear prop-shafts, but which can be locked for off-mad applications. It is this transfer has which produces the familiar Range Rover clonk when drive is taken up or when going onto the overrun.
The FF transmission has a snatch-free chain driven transfer box incorporating a viscous coupling and a differential which, by epicyclic action, provides a 40/60 front/rear torque split, and it is this viscous coupling which prevents more than a few per cent relative movement between the front and rear propshafts — a FF converted Range Rover can be driven with one of the propshafts removed completely. On the FF transmission, the differential is of the epicyclic type. The carrier is the input, the annulus the rear output, and the sun gears provide the front output by way of a chain drive. The difference in diameter between the front and rear outputs (the sun gear and the annulus) provide the unequal torque split, while the viscous coupling acting directly between the annulus and the sun gear shaft limits the relative speeds of the two outputs, thus preventing wheelspin, and also transferring brake torque
from one pair of wheels to the other when the front-rear grip is different in a heavily laden vehicle. The viscous coupling consists of a number of interleaved plates, rather reminiscent of a multi-plate clutch, not actually touching, but running in a special silicon based fluid. This offers no resitance to small speed difference between the
two axles, as are common when manoeuvring in tight spaces, or when accommodating differences in tyre diameter, but the resistance to speed variations rises rapidly if one wheel tries to spin. or to lock. It is because this viscous coupling is fitted that it is possible to incorporate a single. sensor anti-shed braking device. The sensor is fitted to the input shaft of the central differential. and the Mullard devised electronic module reverses the hydraulic line pressure during anti-skid operation by means of a solenoid operated valve fitted to a basically standard servo. The hydraulic lines are hardy altered from standard, and the system is built fail-safe.
Cost? The FF transmission conversion will cost about (2,400 including VAT, and the anti-skid braking system about £1.300 including VAT, although, of course, the latter can only be fitted to a vehicle which has the former. A 12 month warranty is given, and the fitting of these modifications to a new Range Rover does not invalidate the DL Warranty. An expensive business, but the difference is appreciable, and Schuler have a waiting list of customers wanting this treatment for their vehicles. When I returned the rather muddy Super Ranger to Ascot, I was able to haves brief drive in Toby Silverton’s Super Ranger — this one fitted with a 4.4-litre engine, has cam, five-speed box with overdrive fifth. the FF and anti-skid options, lowered suspension, wide wheels and tyres — by way of sampling a Super Ranger converted for mainly road application. Just the sort of Range Rover I have been liable to scorn as being pointless: I still feel it is rather unnecessary, but I did enjoy it, watching 3-litre Capri drivers wince as they were out-dragged frotn lights. . . but that is another story. — P.H.J.W