The Allis-Chalmers HD-11 tractor

Designed as a replacement for an earlier tractor, the Allis-Chalmers HD-11 was a very worthy successor and was in production for over 25 years.  By Richard Campbell

THE ALLIS-CHALMERS model HD-11 was introduced in 1955 as a replacement for the company’s model HD-9, which had been in production since 1950, and the earlier model HD-10, the 10-year production run of which began in 1940.

Both the HD-9 and HD-10 were powered by 71 series GM Detroit Diesels as at that stage, Allis-Chalmers did not manufacture its own diesel engines.

This all changed in 1953 when Allis-Chalmers bought the Buda Diesel Engine Company and began development of its own engines.

Allis-Chalmers introduced several new track type tractor designs in 1955, all powered by the “new” Allis-Chalmers diesel engines.

These included the HD-6, HD-16, HD-21 and the subject of our story, the HD-11.

Rather than just inserting a new powerplant into an existing chassis, the HD-11 was an all-new design from the ground up, utilising experience gleaned from the previous HD-9 and HD-10.

From the outset of track type tractor production, Allis-Chalmers had always been an innovator, developing many of the systems that have been incorrectly attributed to other manufacturers.

Items such as torque converter drive, permanently sealed rollers, power-boosted braking and even sealed and lubricated track (SALT) were all pioneered by Allis-Chalmers.

The first production version of the HD-11 was powered by a six-cylinder naturally aspirated A-C model D-516 engine which produced around 85 flywheel horsepower and had a six-speed direct drive transmission. Track gauge was 74 inches and the machine had a six-roller track frame.

A mid-sized tractor, weighing around 11 tons without attachments, the HD-11 was a contemporary of the Caterpillar D6, International TD-15, Oliver OC-12 and Eimco 106.

By 1958, two improved versions of the original HD-11 were available, the HD-11E and HD-11B.

Primary differences were a change in engine to the new model A-C 10000 series diesel with a consequent rise in horsepower – 99 flywheel horsepower for the HD-11E and 111 flywheel horsepower for the HD-11B, seven roller track frames for each, and a torque converter drive transmission for the HD-11B.

These machines remained in production until 1962 when three new versions were introduced, the HD-11EC, HD-11EP, and an improved HD-11E.

All three were powered by an updated version of the A-C 10000 engine known as the A-C 11000 series which featured for the first time, a turbocharger.

All three machines featured different horsepower ratings.

The direct drive HD-11E was rated at 130 flywheel horsepower, the torque converter drive HD-11EC at 140 flywheel horsepower and the powershift HD-11EP at 150 flywheel horsepower.

Further changes included the addition of oil-cooled steering clutches and brakes, and a 6-roller track frame for all three machines.

In these configurations, all three remained in production until 1971 apart from the HD-11EC which was dropped in 1967 due to declining sales volumes for the torque converter drive/manual transmission type of tractor.

HD-11s saw service in the complete spectrum of earthmoving, agricultural and forestry applications where they were very popular.

In order to retain a competitive edge, Allis-Chalmers undertook a complete redesign of its track type tractor range and this revamp naturally included the HD-11.

Bearing little resemblance to its predecessors, the new HD-11 series B was introduced in the middle of 1971 in two versions, a powershift and a direct drive model.

Still featuring the A-C model 11000 turbocharged engine, the powershift version was rated at 140 flywheel horsepower and the direct drive model at 125 flywheel horsepower.

It was also around this time that Fiat, which had a substantial share holding in Allis-Chalmers, exercised its options and the company changed its name from Allis-Chalmers to Fiat-Allis.

Unfortunately, this was also to lead to the gradual decline of the brand as once Fiat’s influence began to take hold, sales in North America, the brand’s naturally biggest market, began to drop off drastically.

For the HD-11 series B, now known simply as the Fiat-Allis 11B, the writing was pretty much on the wall and the machine was discontinued in 1981, in favour of one of Fiat’s own models, the European-designed FD10.

Sales of all versions of the HD-11 exceeded 16,000 units.

The Allis-Chalmers HD-11 described

Bearing in mind the variety of HD-11 versions, for the purpose of this article, we will take a look at one of the most common HD-11 variants, a late 1950s HD-11B.

As mentioned earlier, the HD-11B was powered by an Allis-Chalmers 11000 series six-cylinder, naturally aspirated diesel engine.

This produced 99 flywheel horsepower at a fairly low 1800 rpm and was connected, via a single plate clutch, to a six forward, three reverse speed constant mesh manual transmission.

Steering was by conventional steering clutches and contracting band brakes which were mechanically boosted to ease operator effort.

Of conventional layout, the HD-11B chassis had a very solid one-piece cast maincase and box beam mainframe and track frames.

Large ‘A’ frames tied the rear of the track frame to the main chassis and a multi-leaf equaliser spring, mounted just past the mid point of the tractor, allowed the frames to oscillate and absorb shock.

Seven bottom track rollers and two carrier rollers per side was the standard format for the undercarriage which had 41 shoes per side, usually 16 inches wide.

Track tension was maintained by a semi-hydraulic track tensioner which was enclosed in oil.

At the front of the tractor chassis, the radiator guard assembly was pivoted at the bottom allowing the assembly to be tilted forward to allow full access to the radiator, an idea well ahead of its time.

The operator was well catered for with a deeply padded seat and armrests and a full instrument display.

Allis-Chalmers tractors were among the first to feature a tapered hood which allowed the operator a better forward view and the rear of the 60 gallon fuel tank was well rounded to allow a better view of any trailed equipment.

Options for the earlier tractors were few apart from a steel-enclosed cab and a heater run off the machine’s cooling system.


Allis-Chalmers, like many other track type tractor manufacturers of the time, did not originally manufacture its own attachments.

This task was left to outside “preferred suppliers” which in Allis-Chalmers’ case were Baker Manufacturing, GarWood, Tractomotive and Carco.

Also, the acquisition of LaPlant-Choate in 1952 gave Allis-Chalmers access to hydraulic technology which was put to good use when the company finally introduced its own line of blades, rippers and shovels (Allis-Chalmers later bought both Baker, Tractomotive and the earthmoving division of GarWood).


There was one significant modification to the HD-11 which deserves a mention and it is the HD-11G model, which was a dedicated track type loader.

Manufactured for Allis-Chalmers by Tractomotive Corp, the type saw service from the late 1950s until 1966 when Allis-Chalmers introduced the model 7G loader which was built from the start as a loader and not an adaptation of a bulldozer.

The New Zealand connection

The Allis-Chalmers was a very popular tractor in New Zealand but unfortunately no importation records have survived, so we don’t know how many came in.

What is known is that the machine sold well; all sub types of the HD-11 were imported from the very early HD-11’s through to the Fiat-Allis 11B.

Many of these machines are still in active service although parts for some of the older models are becoming a little scarce.

For the Model Collector

Dismal pickings I’m afraid, the only model of the HD-11 ever manufactured was to 1:32 scale in the late 1950s and is long out of production.

It is so rare that even the author, an avid model collector, has not seen one!

Brief Specifications: 1959 Allis-Chalmers HD-11E

Allis-Chalmers 11000 series, inline 6-cylinder, naturally aspirated diesel engine rated at 99 flywheel horsepower at 1800 rpm

Single plate, ceramic faced over-centre type, hand operated

Allis-Chalmers constant mesh direct drive type with 6 forward and 3 reverse speeds.

Top speed: 5.7 mph

Multi-disc steering clutch packs, hydraulically boosted

Brakes: Contracting band type with a mechanical booster

Tracks: 41-section

Std. shoes: 16”

Rollers: 7 bottom and 2 carrier per side

Length: 12’ 10” (bare)

Width: 8’ (bare, with 16” shoes)

Height: 9’ 6”

Op. weight: Approx 11 tons (bare)


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