Cat D7D restoration

diesel1 said:

Now that does look like a lot of work

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Fowler VF said:

I managed to rescue an old war ag plough from the scrapman a couple of years back. A single furrow Massey Harris prairie buster. 24" wide and deep. My father said that the war ag used to plough up scrubland with them, burying gorse, bracken the lot. Big knife coulter attached down from the frame to the point, and a set of chains used as a skimmer to drag the brush down into the deep furrow. I did actually use it in anger this year behind the VF, ran around a couple of fields reclaiming conservation margins that had started to creep into the field where min till isn't aggressive enough. Once it had shone up it did a fantastic job, the open furrow was a bit savage though; but at least the edge of the field is now well defined!

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diesel1 said:

View attachment 738228 View attachment 738230 View attachment 738232 View attachment 738234
After a busy weekend blasting and painting shes slowly going back together.
Nose cone on, floor plates on, seat is away at the trimmers, decals are ordered.

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Fowler VF said:

The D7 3T, D7 4T and D7 6T were introduced in mid-1944.

The machines incorporated several improvements that Caterpillar engineers had developed but were unable to introduce due to the necessity of maintaining production of the existing 7M for WWII requirements.

As the urgent demand for tractors subsided these improvements made their way into series production.

The D7 4T was built solely for the US Army while the D7 6T was built for the US Navy.

This enabled Caterpillar to fulfill military contracts that had been let but not completed.

Just over 7500 D7 4T’s were manufactured before the type was discontinued in 1948, and an unknown number of D7 6T’s.

The fate of many of these military D7’s is quite sad as many were pushed into vast pits of surplus equipment and buried while others were just driven into the jungle and left there, some with very few hours on the clock.

This wholesale “jettisoning” of unwanted equipment is what makes the D7 4T a somewhat rare type these days and the D7 6T even rarer.

There is hardly any difference between a D7 3T, 4T or 6T other than the optional external attachments applied to it.

A highly successful variant.
Between 1944 and 1955, Caterpillar manufactured over 28,000 D7 3T models.

With the trusty Caterpillar D8800 engine initially providing 93 flywheel horsepower, this was increased to 108 flywheel horsepower around 1952.

One of the new features Caterpillar had introduced was a forward/reverse lever into the transmission meaning the operator didn’t have to repeatedly shift gears all the time when changing direction.

Other improvements added along the way was Caterpillar’s famous oil clutch and a two-position front idler which better set the machine up for trailed or pushed attachments.

D7 3T’s can still be found doing occasional work some sixty years after the last one left the production line.

The next step
With the D8800 diesel engine now at the upper reaches of it’s development potential, Caterpillar introduced a new version of the D7 in 1955.

This was the legendary D7 17A series, (also known as the D7C).

This featured the all-new Caterpillar D339 four-cylinder diesel engine rated at 128 flywheel horsepower and incorporating all the better features of the previous 3T model including oil clutch, forward/reverse lever plus the addition of the newly developed hydraulic track adjusters, a great labour-saving device which most people take for granted these days.

Halfway through the machines extensive production term, Caterpillar made two crucial changes to the machine.

At serial number 17A11981, a turbocharger was added to the engine, boosting output to 140 flywheel horsepower and allowing the machine to work at higher altitudes without engine de-rating.

Caterpillar also fitted oil-cooled steering clutches and brakes which greatly extended the service life of these components.

Although Caterpillar did not change the serial number prefix of the new improved D7 17A, it did get a new designation of D7D.

These later D7D’s have a distinctive engine note which sets them apart from all other D7’s.

Production of the D7C/D7D had exceeded 19,000 machines when the last one came off the line in 1961.

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diesel1 said:

Went to look at the D7D at oakfields the day before euroauctions was on, ended up with the cat from euroauctions at a lot less money. Was very close to buying the fowler challenger from oakfields when i was there, thinks its sold now.

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Fowler VF said:

The D7 3T, D7 4T and D7 6T were introduced in mid-1944.

The machines incorporated several improvements that Caterpillar engineers had developed but were unable to introduce due to the necessity of maintaining production of the existing 7M for WWII requirements.

As the urgent demand for tractors subsided these improvements made their way into series production.

The D7 4T was built solely for the US Army while the D7 6T was built for the US Navy.

This enabled Caterpillar to fulfill military contracts that had been let but not completed.

Just over 7500 D7 4T’s were manufactured before the type was discontinued in 1948, and an unknown number of D7 6T’s.

The fate of many of these military D7’s is quite sad as many were pushed into vast pits of surplus equipment and buried while others were just driven into the jungle and left there, some with very few hours on the clock.

This wholesale “jettisoning” of unwanted equipment is what makes the D7 4T a somewhat rare type these days and the D7 6T even rarer.

There is hardly any difference between a D7 3T, 4T or 6T other than the optional external attachments applied to it.

A highly successful variant.
Between 1944 and 1955, Caterpillar manufactured over 28,000 D7 3T models.

With the trusty Caterpillar D8800 engine initially providing 93 flywheel horsepower, this was increased to 108 flywheel horsepower around 1952.

One of the new features Caterpillar had introduced was a forward/reverse lever into the transmission meaning the operator didn’t have to repeatedly shift gears all the time when changing direction.

Other improvements added along the way was Caterpillar’s famous oil clutch and a two-position front idler which better set the machine up for trailed or pushed attachments.

D7 3T’s can still be found doing occasional work some sixty years after the last one left the production line.

The next step
With the D8800 diesel engine now at the upper reaches of it’s development potential, Caterpillar introduced a new version of the D7 in 1955.

This was the legendary D7 17A series, (also known as the D7C).

This featured the all-new Caterpillar D339 four-cylinder diesel engine rated at 128 flywheel horsepower and incorporating all the better features of the previous 3T model including oil clutch, forward/reverse lever plus the addition of the newly developed hydraulic track adjusters, a great labour-saving device which most people take for granted these days.

Halfway through the machines extensive production term, Caterpillar made two crucial changes to the machine.

At serial number 17A11981, a turbocharger was added to the engine, boosting output to 140 flywheel horsepower and allowing the machine to work at higher altitudes without engine de-rating.

Caterpillar also fitted oil-cooled steering clutches and brakes which greatly extended the service life of these components.

Although Caterpillar did not change the serial number prefix of the new improved D7 17A, it did get a new designation of D7D.

These later D7D’s have a distinctive engine note which sets them apart from all other D7’s.

Production of the D7C/D7D had exceeded 19,000 machines when the last one came off the line in 1961.

Click to expand...