Overdrive gives diesel Transit longer legs
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by Martin Hayes
WHEN we tested a passenger version of the Ford Transit fitted with the company's York diesel engine back in 1972 we found that, though the diesel offered worthwhile savings in fuel when compared with petrol-engined models, the noise level was rather high.
We said then that "an overdrive ratio could prove useful both in improving fuel consumption and in maintaining higher speeds." Having now had the opportunity to try a Williams Deansgate conversion of the diesel Transit fitted with a Laycock overdrive unit, I can say that this addition can be ful justified for long-distance work.
No exception
The problems caused by the use diesel engines in small vehicles like tk Transit can be overlooked when 11 vehicle is a van. When the load is passel gers, however, considerations of noi! and vibration take on major impor ance. Diesel-engined Transits are n exceptions in this size-range in being m well suited to long-distance psv wonl For short journeys the diesel can tolerated but on high-speed trips the noise can prove too much.
The control for the overdrive is mounted on the steering column on the drivers' right and is clearly labelled. The unit operates on 3rd and 4th gears but there is no "kick-down" arrangement. Fingertip control of the switch is possible, however, without the necessity of removing a hand from the wheel. Engagement of the overdrive was impressively smooth in either third or top, though easing off the throttle helped the process still further.
'No man's land'
Under certain conditions the overdrive refused to engage properly in third. This was usually under hard acceleration but also occurred at lower speeds, when it proved possible to arrive at a strange "no-man's land" when no gear was prgperly engaged. Lifting off in this position produced a free-wheeling situation — scarcely to be desired. I am told that this trouble is probably the result of a fault in the overdrive switch.
When it engaged properly, overdrive 3rd proved more useful than I expected, giving a handy extra ratio for overtaking. However, it is in overdrive top that the device really comes into its own.
Even at low speeds from 56 kph (35 mph) — there were worthwhile reductions in noise without sacrificing tractability. As the speed increased so the value of the overdrive unit increased, too. The manufacturers claim that, when fitted to the Transit, the device saves about 28 per cent of engine revs. Without being able to prove or disprove this figure I can report that highspeed travel in direct drive was nearintolerable by comparison, even though the test vehicle had the highest-available axle ratio fitted.
Though I returned a maximum indicated speed in 4th gear of 103 kph (64 mph)for practical considerations the highest tolerable cruising speed was about 88 kph (55 mph) and even then the radio had to be turned up considerably. With the overdrive a realistic cruising speed of about 105 kph (65 mph) was possible though an absolute maximum of about 113 kph (70mph) was just attainable, given a long spell of flat road.
When we tested a diesel Transit in 1972 it was a loaded 15-seater. It returned a typical fuel consumption on main roads of about 9.2km/1 (26 mpg). The more recent test vehicle was a 12seater but during our 400 km (250-mile). test it was not possible to carry more than four passengers at any one time. Over a varied selection of routes — including commuting in London, fullthrottle motorway work and normal main road use — the consumption figure was almost identical. On longerdistance work where the overdrive would come into its own I would expect a rather better figure, thus allowing significant fuel economy to be achieved.
Well-finished workhorse
Apart from the overdrive — which, incidentally, adds only about 12 kg (261b) to the all-up weight — the test vehicle was the standard Deansgate luxury psv conversion. I was impressed by the standard of finish of the vehicle which gives the impression of being a sturdy workhorse. The conversion is based on Ford's Custom pack which itself provides a number of extras. To this Williams adds seat belts for both driver and front-seat passenger; a second radio speaker in the saloon complete with balance control; indicator board; and a fire extinguisher and first aid kit, both required by psv regs. There is an ash tray and coat hook for eac] seat or pair of seats.
The main entry is through the near side front door which provides reason able space, though the available he* is somewhat restricted. An emergenc exit is at the rear. The seats themselve are surprisingly comfortable, thoug some — particularly over the who arches — are rather cramped for kne( room.
Rattle-proof
The fixtures and fittings proved con mendably rattle-proof. Surprising: there was very little vibration whe idling — normally a bad feature of sma diesels — though the clatter from tl engine tended to be rather obtrusiv One of the few failings of the conve sion, it seemed to me, was the drivir seat. The standard Ford seat is us( which is quite acceptably comfortabl On non-psv vehicles this is fully adjus able for rake as well as height and for and-aft position. Apparently because psv regs, the seat back has to be fixed one position. On the test vehicle t position chosen was a fierce 90 degre which proved very uncomfortable f most drivers. It would be infinite better for most drivers if a more rak position had been selected, though the of less than average stature might th object.
The Deansgate-converted Tran complete with diesel engine and ovi drive costs about £2,900 complete. T overdrive option, also availal on petrol-engine models, costs abc £151 of this and at this price seems w worth the money. Apart from potent fuel savings the device's great advantage is the way in which it exter the range of the diesel derivative to hil speed, long-distance work.