Classic MachinesTractors

The Oliver OC-18 tractor

In its heyday, the Oliver Corporation of Cleveland Ohio, USA was a well-respected company manufacturing agricultural tractors and implements. By Richard Campbell.

Looking to expand its marketplace options beyond agricultural wheel tractors, it acquired the Cletrac Tractor Co, also of Cleveland Ohio, in 1944.

Cletrac had fallen on hard times during WWII, being one of the few tractor manufacturers not to be given large war contracts for the production of machinery, so the sale to Oliver was very timely and prevented the company going into bankruptcy.


Cletrac had a long history dating back to 1916, and was one of the pioneers of the track type tractor industry.

In fact Cletrac was the first company to manufacture a “hi-drive” (elevated sprocket) track type tractor on a production basis, its Model F, which was produced from 1920 to 1922, pre-dating the Caterpillar D10 by 57 years!

The Model F was a small crawler tractor strictly speaking only suitable for agriculture and weighed around 900 kilograms, but could pull a 3-bottom plow with no trouble.

One of the hallmarks of Cletrac tractors was their reliability, especially final drives.

This was due to the way the track frames were mounted to the chassis by way of a dead shaft.

Using this method, no impact shocks were transferred through to the final drives.

It also allowed a higher than usual amount of ground clearance, making Cletrac machines especially popular with logging and forestry contractors as they could pass over stumps and brush that could potentially bring other tractors to a very sudden stop!

Other track tractor manufacturers took a long time to duplicate this method of undercarriage attachment with the first to successfully adopt it being Euclid in the mid-1950s.

From 1936 until the Oliver buy out, Cletrac used an alphabetical system to identify individual models within its product range, eg, Model BD, Model DG, Model AG etc.

When Oliver took over the Cletrac tractor range it consisted of some 12 different models, some gasoline powered, the others diesel.

Oliver kept the Cletrac name, marketing them as Oliver-Cletrac so as not confuse the buying public and it was business as usual.

In 1949, it was decided by Oliver management, to add some clearer structure to the model numbering system, better reflecting the sizes of machines offered.

The Cletrac name was dropped altogether and a new machine identification system “OC” (Oliver-Cletrac) prefixed all the track type tractors.

With this system in place, machine models included the OC-3, OC-4, OC-9, OC-12, OC-15 and our subject this month, the OC-18.

Oliver as a company did not expend great amounts of research and development money on its OC track tractor range.

This was unfortunate as ‘resting on its laurels’ allowed other manufacturers to get the jump on it.

Sales started to decline as the existing machines were being surpassed by better technology.

Things came to a crunch in 1960 when Oliver was bought by the White Motor Corporation.

White continued to operate Oliver as a going concern but was also reluctant to spend the large volumes of cash required to update the Oliver track type tractor range.

The end result was that in 1965, production of all Oliver track type tractors was discontinued, the company preferring to concentrate on agricultural wheel tractors.

The Oliver OC-18 described

The Oliver OC-18 was the largest track type tractor that Oliver ever produced and sat between D7 and D8 size in the track tractor world.

Some 800 were manufactured between 1951 and 1959.

It had originally started out as the Model FDE in 1945 but was extensively redesigned by Oliver engineers and re-emerged as the Model OC-18 in 1951.

Oliver used a Hercules model DXFE diesel engine in the OC-18.

This engine was a 6-cylinder inline diesel putting out 161 flywheel horsepower and had a 14.7 litre displacement.

A double plate clutch connected the engine to the 4-forward, 2-reverse speed manual transmission which gave the machine a top speed of 5.4 miles per hour.

Oliver was unique in the American track type tractor market by using differential steering rather than the traditional steering clutch and brake method.

Cletrac had pioneered the use of differential steering decades beforehand and it was carried over into the OC range of machines.

It wasn’t until the 1990s that other manufacturers began to use this steering method.

The OC-18 was a 78″ gauge tractor and utilised a 6-roller track frame with two carrier rollers per side. Track links were 35-section and the standard track shoe was a single grouser, 26″ wide.

As mentioned previously, the track frame was isolated from the final drives and attached to the chassis by means of a large deadshaft, which, along with the multi-leaf equaliser spring, allowed track oscillation of some ±13″.

A good spotting feature of the OC-18 was its long front hood, the rear part of which housed the 66 gallon diesel fuel tank.

Oliver supplied its larger crawlers with a distinctive opposed chevron design radiator guard and the OC-18 was no exception.

The operator had an excellent view to trailed equipment as there was no fuel tank to look over. However, the view forward was a long one and the hood did not feature any taper.

Operator comforts were very few other than a deeply padded seat and air-boosted steering levers to reduce effort.

This was an unusual feature for a track type tractor and something that set the OC-18 apart from the competition.

An engine-driven air compressor provided constant pressure for the system.

Full instrumentation was provided on a semi-circular instrument panel in the centre of the dashboard.


Oliver did not make its own attachments and relied on outside suppliers to provide bulldozer blades, rippers, cable controls and the like to equip the OC-18 for service.

Principal suppliers were Heil, Isaacson, Buckeye and Carco with the most predominant of these being Heil.

The New Zealand connection

New Zealand distributor for Oliver-Cletrac was Frederick W. Smith Ltd.

Regrettably, no records have survived from this company to give any indication as to how many Oliver OC track type tractors were imported including (if any) OC-18s.

There were certainly a great deal of the smaller Oliver OC tractors brought into New Zealand however, and these proved to be very popular, especially in the South Island.

The author would be keen to learn if any OC-18s made it to New Zealand as he’s never come across any on his travels.

For the diecast model collector

Very slim pickings here with no models of the Oliver OC-18 being available at all.

There is however a remarkably good model of the smaller model OC-12 available from Spec-Cast.

This is to 1:16th scale and is available with or without a hydraulic blade.

The model is generally available through eBay for under US$150 and makes a fine display piece for those of you who collect larger crawlers.

Brief specifications – Oliver OC-18

Engine:            Hercules DFXE, inline 6-cylinder, naturally aspirated, rated at 161 flywheel horsepower at 1500 rpm

Clutch:            15″ double-plate, overcentre

Transmission: Constant mesh manual, 4-speeds forward, 2 reverse

Top speed:      5.45mph

Steering:          Differential type, air assisted

Brakes:            Contracting band

Track gauge:    78″

Tracks:             35-section

Rollers:            6 bottom and 2 carrier per side

Standard shoes:           26″

Length:            14′ (bare)

Width:             8′ 6″ (bare)

Height:                        6′ 10″ (bare)

Operating weight:       16 tons (bare)

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