Rear PTO

One of the very first pieces of optional equipment available for the Land Rover was the rear PTO. This simple gearbox, with a 5:6 ratio, attached to the rear crossmember and was driven by the centre PTO via a propshaft. It allowed the Land Rover to power pieces of equipment around the farm that had up until now been reserved for stationery engines and tractors. It was a big part in fulfilling Maurice Wilks’ dream of creating the World’s most versatile vehicle.  The PTO idea was so important to Wilks’ vision that the ‘centre-steer’ prototype was fitted with a rear PTO, possibly from a Jeep, demonstrating just what the future Land Rover could be asked of and expected to do.

When the Land Rover was being developed, many farming practices were undergoing a revolution with improved mechanization and standardization; the most notable of these was the Ferguson System used on the little grey Fergie tractors. By the early 1930’s, the six-spline output shaft and the PTO shaft speed of 540rpm was adopted as the American Society of Agricultural Engineering (ASAE) standard and was soon used across the World. It was these advances in farming practices that would eventually lead to the conclusion that the Land Rover would never replace the tractor but could work alongside it.

Rover initially designed their own rear PTO with a ten-spline output shaft, fitting them to the first 400 units. The ten-spline output shaft severely restricted its use and Rover soon made available a ten-spline to six-spline adaptor.  To compliment the ten-spline rear PTO output shaft, a similar amount of 8in flat belt pulleys with a ten-spline input shaft were also manufactured. In the late 1940’s and 1950’s, flat belt powered equipment was still popular, if not slightly outdated but production of the flat belt pulley soldiered on well into the 1980’s. The first production rear PTO's had added strengthening webs in the gear casing. After the first 400 units, the ten-spline shaft was replaced with the now SAE standard six-spline shaft allowing the Land Rover to power a wider range of equipment and implements. The gear casing was also soon modified and the breather that was previously positioned directly above the input gear was now moved on to a new piece of casting to the left of the input gear, along with the addition of an oil drain plug. The flat belt pulley input shaft was adapted to suit along with the introduction of a rear capstan winch.

PTO’s fitted to pre-production Land Rovers often carried the serial number of the vehicle they were fitted to but production PTO’s had there own set of serial numbers beginning at 8600001. The numbering system was consecutive and did not change prefix when a new model year started, unlike the vehicles. Although manufactured by Aeroparts Engineering, they did not carry the AEH numbering system as seen on the capstan winches and hydraulic winches. The numbering system continued up until the 1970’s when the serial numbers was replaced by the Aeroparts green makers plate.

By the mid 1950’s the limitations of the Land Rover PTO were all too apparent, especially when live PTO clutches were becoming common. The main disadvantage of the Land Rover PTO is when the vehicle is powering an implement while on the move. When the vehicle clutch is depressed, drive to the PTO is also disengaged, causing a number of issues depending on the piece of equipment being powered. The speed of the PTO output shaft is also dependent on the speed of the engine and the gear selected in the main gearbox, unlike a tractor that by now could maintain a constant 540rpm at the PTO. The Land Rover system gave a very narrow margin at where 540rpm could be achieved and this was not necessarily at the most efficient forward speed or torque for the engine, however on paper this was in first gear low ratio at 1950rpm, corresponding to max torque of the engine. Very early vehicles were fitted with lower geared 4.88 ratio differentials that helped with the balance of speed of the vehicle to the speed of the PTO but when the 4.7 ratio diffs were introduced to improve on road performance, achieving this balance was made much harder. In a bid to help keep the idea alive, Rover stated you could swap the gears over in the PTO resulting in a step up ratio of 6:5 but this was at a sacrifice to the engine torque.  The size of the tyres fitted to the vehicle also contributed to a difference in the gearing and speed.

For static work the Land Rover could be used quite effectively and found some success in industrial applications such as welder and compressor vehicles. The cost of these been the biggest drawback. Many of the early welder and compressor conversions had restrictive, permanently fitted equipment but eventually they found a new home mounted in special frames replacing the rear tailgate and powered by a V-belt pulley mounted on the rear PTO. This allowed a vehicle to be returned to its standard state within a couple of minutes. It is also worth noting that the six-spline shaft could be replaced with a drive flange, which was an input shaft and flange being used as the output. The Land Rover rear PTO was capable of transmitting a maximum of 25BHP and the flat belt pulley a maximum of 20BHP.

The Land Rover suffered without the option of a Diesel engine until 1957. Most tractors had moved away from petrol, and besides a relatively brief period of tractors using a mixture of petrol and TVO, they were now using much cheaper Diesel. An engine governor manufactured by Iso-Speedic was deemed necessary by Rover when using a Land Rover fitted with a petrol engine for PTO work. The later Diesel engine did not require this extra expense and had the advantage of better fuel economy and other safety factors when used in an agricultural environment. With the governor and hand throttle fitted, one of 44 speeds could be chosen ranging from 415rpm to 2500rpm at the rear PTO. The flat belt pulley had a range of speeds from 360rpm to 2145rpm when fitted to petrol vehicles, however difficulty would be experienced in holding the vehicle steady if more than 20BHP was transmitted through the pulley. In addition to the engine governor, Rover also recommended an engine oil cooler should be fitted.

To keep the operators safe, a shaft guard was made available. There appears to have been three notable types, the first found on pre-production models was a very simple folded steel assembly and quite small. The second arrangement was much larger with neat curves and an inspection hole on the top surface. The final version was an adaptation of the second type but now had a slot cut to accommodate a removable rear cover plate.

The design of the rear PTO remained unchanged until November 1968 when the aluminum bearing carriers were replaced with steel to strengthen them following concerns over breakages. This was the last major design change of the rear PTO until it was adapted for use with the early 90 and 110 when the gear casing was now mounted inboard of the rear crossmember. The input and output shafts were swapped, with the output shaft now considerably longer to protrude through the rear crossmember.

There were a number of propshaft lengths used to attach the centre PTO to the rear PTO depending on the vehicle’s wheelbase and engine. The Series One 80in propshaft was unique to the 80in, whereas the propshaft length used on the Series One 86in was also used on the Series One 88in, Series 2, 2a and 3 88in. The same propshaft was also used as the first half on the Series One 107in, 109in, Series 2, 2a and 3 109in four cylinder vehicles. Six cylinder 109in Series 2a and 3 had a slightly shorter first propshaft. On Long Wheelbase vehicles an additional crossmember was fitted and this was used to support the two propshafts where they joined. All Long Wheelbase vehicles used the same length propshaft for the second half. Furthermore if the a rear PTO was being fitted to Long Wheelbase six-cylinder vehicle or the later Long Wheelbase four-cylinder Series 3 with the rear fill fuel tank, a special narrow fuel tank of less capacity was fitted in order to give clearance for the PTO propshaft.

The rear PTO was never a cheap option, costing £20 in November 1949 with the flat belt pulley costing a further £15. By 1967 a rear PTO would now set you back £44.5s.0d with a pulley an additional £28.5s.0d. In 1976 a rear PTO would now cost £225 and a rear pulley £140.

The rear PTO is another great piece of optional equipment that always draws interest and questions at Land Rover shows and Steam Rallies, yet can still be purposefully used by the smallholder, market gardener or general enthusiast.