Heavy Haulage History: Leyland Marathon & Marathon 2 (1973 – 1980)

 Mike Humble


A Prototype Leyland Marathon at Southall in 1972.
An early pre production export spec Marathon at the Southall AEC works 1972.

The start of the fightback

Adapting to market changes – and fast:

After all the trials and tribulations over the past three decades, one of the key members of the British Leyland Motor Corporation still prospers and survives. Leyland trucks based in the Lancashire town of the same name still produces commercial vehicles for the DAF group trading under the independent title of ‘Leyland Trucks Ltd’. Other BLMC names such as Albion, Guy, Scammell and Thorneycroft have sadly joined the roadside cafe in the sky. But against all odds, Leyland survives.

One of the main reasons for this was due to the epic investment bestowed upon them in the late-’70s during Sir Michael Edwardes’ chairmanship. His (some say) rather harsh policy of only bailing the departments that justified the investment certainly paid off at Leyland. The T45 range and test track along with state of the art laboratories gave the truck town a new lease of life. The assembly plant known in the trade as LAP is one of the most efficient in the world but the story of truck building within Leyland is a book on the horror shelf and far off being a fairy tale.

If we cast our minds back to the 1970s, foreign imports were at first resisted by the UK hauliers that was until Volvo introduced the F86/88 range of tractor units. They were without doubt utterly superior in every way to anything that was built in England. Comfort, space, performance, reliability – even style were all part of the Volvo package and UK brands like Atkinson, ERF, Foden and BL were simply outclassed on every conceivable level. The ever sprawling motorway and trunk road network was shrinking journey times along with transport profit margins.

This V8 powered AEC Mandator with special high roof conversion matched European rivals for power but fell far short for space or sophistication.
The Mandator V8 with high roof and sleeper was impressive on paper. In practice however, a spectacular failure.

Initial prototype ideas that failed dismally:

Your typical English truck operating at 32 tons would be fitted with a Gardner engine if you were lucky, up to 180bhp from a lumbering 10.45-litre non turbo diesel. The Volvo F88 was blessed with a smaller engine, yet featured turbocharging and superb engineering to give even the base model 265bhp with options up to 320. Of course, you could order certain UK trucks with a 220 Cummins engine at a hefty cost, but back then Cummins had an uncertain reputation. The relaxation of certain rules regarding haulage meant UK operators could ply their trade on the Continent but our trucks were simply not up to the job.

Leyland and AEC had made some improvements to their mid range line up in 1965 in the form of the Ergomatic cab and thanks to owning many once previous rivals, the board sanctioned the development of a new type of heavyweight tractor unit. Finances were tight as BL were going through a tough time so all efforts were made to keep development costs to a minimum by using as many existing components as possible. Finding a suitable engine range was a difficult solution to overcome, the recent AEC designed 800 V8 was nothing short of a flop as was the 8.3 litre Leyland 500 series.

BL management had sanctioned the development of what was known internally as project ‘FPT 70’ – a joint committee between AEC – Guy Trucks and Leyland with most of the engineering taking place at AECs Southall plant. This would have blossomed into a range of transcontinental heavy haulage tractor units capable of operating at 44 tons and beyond. After the hurried introduction of the 800 series engine causing untold warranty and reputation issues (partly due to BL management rushing into full scale production, the project was scaled back to a manageable and more cost efficient plan using as much existing tooling as possible.

AEC designed this prototype '3TVG' in 1968 - the Marathon that could have been?
Another AEC / Leyland failure was this experimental V8 3VT project.

Make do and mend – British Leyland Style:

The plan still concentrated on long distance haulage, but the idea of a turbocharged state of the art BL V8 diesel faded away as escalating costs continued to thwart the V8. Huge damage was done to the proud reputation of AEC as Leyland raided the cupboards for ideas at any cost with the disastrous 800 series engine being just one example. Senior staff at Southall felt that AEC were viewed as ideal Guinea Pigs in order to save the face and name of vastly larger Leyland name. Eventually, the V8 engine was rightly deleted but this left a problem with regards to higher power engines.

The only suitable power units in the group were the Leyland 11.1 litre 0.680 or the AEC 12 litre AV760. Leyland had turbocharged the 0.680 with mixed success into the 0.690 range, but cylinder head gaskets were prone to blowing at higher power levels so the robust AEC AV760 power unit was re-worked with different fuelling systems – notably a Bosch pump, revised head porting to improve breathing and newer designs of pistons into the Leyland TL12 engine that developed a healthy 273 bhp with excellent bottom end strength and torque. Lower power options were from the Rolls Royce Eagle (220bhp) and bigger power from the 335bhp Cummins E14.

The cab was nothing more than a BL ergomatic design that was placed higher on the chassis, but a first for Leyland included a factory made sleeper cab option. Pre production of the Marathon range commenced in 1972 at the former AEC plant in Southall West London and initial impressions of the truck by motoring journalists were pretty good, with favourable remarks regarding the engine power and performance of the TL12 unit & Fuller gearbox. Early examples were far from perfect in service, leading one or two operators to remark the truck was called ‘Marathon’ purely because 26 miles was about the distance between problems.

After the impressive yet flawed V8, BL opted to develop existing engines or buy in from Cummins or Rolls Royce.
Following some expensive mistakes such as the 500 series and the 800 V8 seen here, future high power engines would be developed from existing Leyland units.

Cost cutting that showed

After entering production in 1973, the Marathon faired reasonably well in road test features with notable mention of the performance of the truck, even in 280 format. Initial sales of the Marathon were pretty good considering it was more than obvious that the truck was developed on an embarrassingly small budget compared to Foreign rivals.  Once some serious grafting and mileages occurred, in true British Leyland tradition, its shortcomings came to the fore. Engine and drivetrain speaking, the Marathon was pretty robust but ancillary components were were either not fit for purpose or lacking in quality.

Its heater and ventilation unit was carried over from the smaller GKN built “ergomatic” cab, in the lower height vehicle the heater was only just about adequate but in the much loftier Marathon, simply failed to provide the driver with sufficient heating. The cab suspension was way too flexible which caused alarming levels of roll under hard cornering or evasive action. The latches on the larger than normal cab doors failed regularly and thanks to a misunderstanding in communication, the shock absorbers were wrongly specified causing a shocking ride standard and premature failure of the tapered leaf springs.

Initially, the Leyland power unit occasionally gave gasket and timing gear problems, but AEC possessed some first rate engineers who worked hard at curing these matters. A Leyland group rear axle (made by Albion) was fitted to all Marathon’s which gave a musical whine that became characteristic of many later Leyland trucks. Hub reduction with epicyclical gearing featured on these but early models operating at the higher power levels had the axle working under maximum capacity, but again, once this was found to be the case engineers upped the strength and tackled the problem.

The Marathon in its earliest guise looked impressive and imposing, but some serious quality matters gave operators grave concerns.
By the time the Marathon entered production, plans were set for the T45 range. The Marathon became Leylands truck and bus version of the the Marina – a make do stop gap solution.

Problems in service:

The two major worries of the Marathon revolved around the braking system, again, all due to British Leyland management pressurising AEC into rushing the truck into production despite pleas from engineers and development staff. The trunking of the air piping to close to sources of extreme heat or vibration lead to air leaks or at worst – total fracture of the high pressure lines which in turn would cause the spring actuated brakes to jam on under total pressure loss. But it was the performance of the service brakes that gave many operators and drivers the biggest concern.

Unlike a modern truck that has the footbrake actuator valve under the pedal, the Marathon’s actuator was mounted in the chassis frame and operated via a cable from under the pedal which needed to be adjusted with precision  Too little slack in the cable caused brake binding or in extreme cold caused the brakes to be stuck on, whereby too much slack meant an alarming amount of pedal freeplay and lack of efficiency even if the pedal was buried into the floor. One or two accidents lead to Leyland modifying the system in service with a complete redesign coming on stream in later models.

Despite certain matters revolving around blatant cost cutting or quality, the truck itself performed quite well. The Leyland TL12 engine gained a reputation for being one of the best units developed by BL with high mileages without major dilemmas being noted. Leyland subsequently went on to redesign the interior with better quality components, brake systems were modified and improved along with a raft of updates and revisions enough to justify re-launching the truck as the ‘Marathon 2’ in 1977. By now, the T45 range was signed off for future production, so Marathon was left to coast along until replacement.

The Marathon 2 from 1977 became an excellent truck giving Leyland a huge boost and earning them a truly massive Government investment for future developments.
Despite some quality related problems, the Marathon was developed into a reasonably acceptable and decent truck.

Marathon 2 – Tried and tested to pave the way for the future:

Being easy to knock a BL product, the Marathon was generally well received in the industry actually selling in better numbers than some reports might have suggested. Some interesting proving tests found models seeded in Transcontinental haulier fleets for evaluation with every opportunity taken to make good use from maximum publicity. BL test driver Richard Rivers found himself behind the wheel of a Marathon 2 and being filmed in places afar afoot as Doha. Leyland even went as far as producing a model with extreme operation conditions in mind called the ‘Marathon Special’ – even air conditioning could be specified.

A memorable story I was once told about the Marathon came from a father of a friend from school who worked as an owner operator transporting Teesside steel to Saudi Arabia. On one journey fully freighted with steel pipework the truck developed a hole in one of the pistons on the TL12 engine. Being more than capable, the driver and his mate dropped the sump, pulled out the offending piston, placed a jubilee clip round the crank journal to keep up the oil pressure, blanked off the relevant fuel injector and got the truck to the delivery point – and back to the UK on 5 cylinders. He swore by that truck he ran for over 10 years.

British Leyland closed the AEC plant in 1979. Marathon production moved to Scammell in Watford with TL12 engine production moving to Leyland. Plans for the award winning T45 range had been signed off as far back as 1976, but it wasn’t until 1981 that full scale production commenced. The Roadtrain used the same chassis albeit improved as the outgoing Marathon and even used the TL12 as the standard engine which by now had a good reputation up to 1983. By now, Leyland had made huge advances in braking and cab design and the Marathon based T45 earned the accolade of Truck of the Year 1981 – Leyland had completed their Marathon task!

The last Leyland Marathon reaches the sign off dept of the AEC Southall factory – not only the last truck built there but also the end of the factory – The works closed for good just days later. Production moved to Scammell Motors at Watford until the Leyland assembled T45 Roadtrain came on-line in 1980.

Leyland Marathon Specifications:

  • 220 or 265bhp – 12 Litre Rolls Royce Eagle 800 or Eagle 800 turbo
  • 280bhp –  12 Litre *Leyland TL12 (Flexi-Torque)
  • 335bhp –  14 litre Cummins E Series

* = The TL12 was a heavy re-work of a previous AEC unit known as the AV760

One comment

  1. For many years (at least up to 2000) there was a fleet of Marathons running round the Land Rover Solihull factory in varying states of decrepitude/astronomical mileages – I wonder if any still survive?

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