The IH TD-25 tractor

Following on from its very successful model TD-24, International Harvester introduced its successor, the TD-25 in 1959. Rather than being a scaled up version of the TD-24, the TD-25 was a completely new machine.

The former TD-24 had not been without its faults, which, over its production life, International had tried very hard to iron out. Basically these problems took the form of transmission failures and cylinder head cracking and were caused in part by rushing the machine into service without adequate testing in order to compete with Allis-Chalmers’ HD-19. While many improvements were made, International never completely cured the head-cracking problem despite several modifications to the design.

International was determined not to make the same mistake again. Size-wise, the new TD-25 competed head on with Caterpillar’s D8H and Allis- Chalmers’ new HD-21 – both formidable tractors in their own right.

Initial deliveries of the machine commenced in 1959 and it quickly became apparent that International had made a really good tractor. Both power shift and direct drive versions of the machine were available. An improved model TD-25B was released in 1962 featuring more horsepower(up from 230 to 240hp) and some minor refinements to the shape of the sheet metal on the bonnet & radiator guard.

The TD-25B was a popular tractor and sold in quantity.

Following on the success of the TD-25B came the TD-25C in 1974 with a further increase in horsepower, now up to 285hp, and a weight gain of almost  two tons over the previous TD-25B.

Another feature was the completely revised hood assembly which was considerably more rounded than its predecessors.

The last model that International Harvester had anything directly to do with was the TD-25E introduced in 1979.

Following this, International’s earthmoving division was sold to Dresser Industries and Dresser continued to build and market the TD-25E and introducing a TD-25G in 1984.

By now, the machine produced 320 horsepower and was far removed from the original TD-25.

Following significant losses by Dresser in 1987, Komatsu entered the picture and picked up a 50 percent share in Dresser. Komatsu had no need for a track type tractor line as it already had a very successful one of its own so the Dresser track type tractors were sold to HSW Industries of Poland in 2005 where the TD-25 continues to be produced today, now known as the Dressta TD25H

The TD-25 Described

We will examine the TD-25C model which, to date, is the most widely produced version of the TD-25.

Power was provided by an International DTI817B, 6-cylinder, turbocharged and aftercooled diesel rated at 285 flywheel horsepower. This was connected via torque converter to a 2-speed powershift transmission with a high and low range, effectively giving the machine 4 forward and reverse speeds. It is worth noting at this point that International also offered a manual transmission option for the TD25C featuring 8-speeds and an oil clutch.

A very substantial tub with bolted on side frames formed the basis of the chassis. Track frames were massive and held seven bottom rollers and two carrier rollers per side. The frames were pivoted at the rear through the double reduction final drives and kept in alignment by a pinned equalizer bar which allowed track oscillation of some 17 inches.

Recommended standard track shoe was 22 inches although, of course, other options were available depending on customer requirements. Steering was of the planetary type with both tracks powered at all times. Each track had high, low or neutral positions that allowed gradual or sharper turns.

A very wide and clean deck area was provided for the operator who sat in a deeply cushioned seat. From the seat visibility was very good all round including to the rear over the contoured fuel tank. Controls consisted of the transmission control, set in a short pedestal to the operator’s left, steering levers which projected out from under the seat and the blade or other implement controls to the right, the configuration of which changed considerably over the years.

The only pedals on the deck were the decelerator and master brake. From the ‘C’ model onwards a ROPS cab was available as an option along with the usual creature comforts of heating and air conditioning.


Almost every kind of attachment imaginable has been hung off a TD-25 during its long career, however the standard items offered by I.H. consisted of a 13’ straight or ‘S’ blade, 15’ angle blade and 18’ full ‘U’ dozer.

These could be cable or hydraulically controlled (hydraulic only after the ‘C’ model) and were manufactured by I.H. inhouse rather than supplied by Allied or Bucyrus-Erie who had built the attachments for the former International TD24.

Radial arc or parallelogram rippers manufactured by International, Ateco & CRC-Kelly could also be fitted. The earlier machines that had a rear cable control usually had an I.H. manufactured item although a Caterpillar No.29 would also fit.

In logging applications some TD25s were fitted with Hyster winches but by far the favoured type was the Carco F50.

From the Operator’s Seat

Your author has spent a bit of time at the controls of TD-25s, mostly TD25B machines pulling Cat 463 scrapers. An excellent scoop machine, the B & C models had plenty of power for the job at hand and gave a comfortable ride.

With power available continuously to both tracks, cutting into the toe of a hill was particularly easy when towing a scraper with a TD-25.

The New Zealand Connection

International Harvester of New Zealand imported well over 100 TD-25s of all series, and these have served throughout New Zealand in all manner of civil works from logging through to dam, airport & highway construction.

Major users of the type included Dryden Construction, Taylor & Culley, NZ Roadmakers, H.Allen Mills and Earthmovers Waikato. TD25s of various ages are still operational throughout New Zealand.

For the Diecast Model Collector

Several examples of the International TD-25 are available in model form. Without a doubt the best of these are made by First Gear and are available in 1:87th, 1:50th and 1:25th scales.

All of First Gear’s models represent a late production TD-25C with the 1:25th scale version being of museum quality.

The 1:25th scale TD-25C has been issued at least six times by First Gear in different configurations including a pipelayer variant which is truly impressive.

There is also an Ertl/Eska model of a TD25 ‘A’ model which was manufactured in the 1960s to approx 1:25th scale.

It is a fair reproduction for the time period but is, however, quite expensive as it is regarded as a collectors item.

Brief Specifications – International Harvester TD-25C

Engine: International DTI-817B, 6-cylinder, turbocharged and

Transmission: International/Twin-Disc full powershift transmission with aftercooled diesel rated at 285 flywheel horsepower at  2200 rpm. integral torque converter, 2-sp fwd and rev with hi/lo shift giving 4 effective speeds in each direction.

Brakes: Wrap around contracting band.

Steering: Planetary, full power with multiple disc clutches.

Top Speed: Approx 6 mph.

Rollers: 7 per side std with 2 carrier rollers on each track frame.

Track Shoe: Std 22” (other options available).

Track Chain: 38 section, sealed.

Length: 28’ approx with S blade & ripper.

Width: 13’ (with S blade).

Height: 10’ 5” to top of stack.

Operating Weight: 34 tons approx with S blade & ripper.

The International TD-25 tractor

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