A classic Ford tractor in two different sizes!

Jonathan Whitlam explains why, back in the mid-1970s, Ford decided to offer farmers the same tractor in two different sizes.

On a recent visit to the premises of collector and agricultural contractor Paul Reeve, I could not help but notice that two of his many classic Ford tractors were parked round the back together, after doing some work. 

These were not just any Ford tractors though, they were a 6610 and a 6710 – the same basic tractor, but in two sizes. Parked side-by-side the differences are clear, but to find out more we need to go back further in time beyond 1981, when these two models first appeared, because the origin of this rather unique aspect of tractor design has its roots back in 1975 and 1976.

Towards the end of 1975, the original Force range of Ford tractors was updated into the 7A1 range, known to all outside of Ford as the 600 Series. These tractors were a step up from the older range, with many improvements, in terms of mechanical specification, and performance. 

The 6600 was the model that replaced the 75hp 5000 as the largest naturally-aspirated four-cylinder tractor and was rated at 78hp. It had been planned for the new range to also be fitted with the new ‘Q’ cab that Ford had in development, but this was running behind schedule and so the range was introduced with the same FIECO safety cab as the earlier tractors being replaced. 

This was only ever intended to be a short-term measure as, the following year, new legislation limiting the amount of noise permissible at the driver’s ear was coming into force and required manufacturers to develop quiet cabs.

May 1976 would see the launch of the new ‘Q’ cab and the change of designation to the 7A2 range to denote this, although to everybody else it continued to be called the 600 Series. Now with the elegant, and very practical, Ford quiet cab fitted, the 6600 finally reached its potential and became a strong seller in the range.

Then, in August 1976, the 700 Series was launched by Ford, consisting of two new six-cylinder models, the 8700 and 9700, that topped out the Ford range, and at the same time two new four-cylinder models, the 6700 and the 7700, were introduced. The idea behind these four-cylinder models was that these tractors, built to a much higher design and with a flat floor to the cab, were to be designated as ‘luxury’ versions of the 6600 and 7600. 

This was certainly the case, as the smaller tractors were very cramped in comparison, with their cab straddling the transmission hump and with centrally-mounted gear levers. In contrast, the 6700 and 7700 had their gear levers mounted to the right-hand side of the cab floor and had all the hydraulic and power take-off controls mounted to the right of the driver’s seat on a neat console. This really was the lap of luxury!

When it came to engine and transmission, these tractors were identical to the 6600 and 7600. The differences were most definitely in stature and styling, although the design also included a wheelbase that was 14 inches longer, giving a more stable and comfortable ride for the operator, as well as more room for the various ancillary items.

The idea for these four-cylinder 700 Series tractors was firmly rooted in North America where, for a long time, tractors were being designed to a higher build to meet the needs of farmers that required a row-crop tractor to work within and above growing crops. 

Ever since the 1960s, row-crop versions of the 5000 had been built in North America to meet this need and the 700 Series was seen as a modern extension of this requirement.

The four-cylinder 700 Series tractors did not sell as well as the smaller 600 Series versions, mostly due to the higher purchase cost of the luxury variants. It was also found that the models in the 700 Series were quite a bit heavier than the smaller versions and, although this was not a huge problem for the 7700, it did make the 6700 look a bit of a ‘lump’ in comparison with the sprightlier 6600. 

Ford even built a 5700, based on the 5600, for certain markets, but this must have seemed even more of a ‘lump’ and was not sold in the UK. Both the 600 and 700 Series were built in Basildon, in Essex, and at the Romeo factory in the USA, with production finally settling on the Basildon plant alone the following decade.

The next big development regarding these models was the engine upgrade that came along in 1980, when Ford managed to make the four-cylinder engines more powerful by increasing their internal dimensions slightly. This meant that the 6600 was now an 86hp tractor, while the 7600 boasted 103hp. 

The new, more powerful models were known as the Power Plus range and the 6700 and 7700 also received the same treatment, as they were still based on the 6600 and 7600. This was the last evolution of these models, as a new line-up was waiting in the wings.

Series 10
September 1981 saw the new Series 10 tractors unveiled to the world. New styling was evident on the smaller models with the straddle-type ‘Q’ cab, with the 6610 and 7610 now replacing the 6600 and 7600. The engine was the same as the Power Plus versions, so horsepower remained the same as previously. 

What was new though, was the Synchroshift transmission. This was the first synchromesh transmission to be fitted to a Ford tractor and the whole Series 10 range was offered with it. On the smaller tractors it was controlled by a column-mounted gear shift, leaving the floor uncluttered, while on the larger 6710 and 7710 with their flat floor, the right-hand, floor-mounted gear levers were retained.

With Dual Power fitted, the new gearbox was a 16 forward, eight reverse unit, giving a pretty good spread of gears for everyday use, although the column-mounted gear change of the smaller models was something of a challenge to get used to and was not logical in operation. 

It soon became a very unpopular feature and probably did make some people opt for the 6710 and 7710 instead, while some users probably felt it was a worthwhile investment spending more on the tractor to not have to deal with the ‘Rubik’s Cube’ gearbox, as the column change soon became known!

With 86hp under the bonnet, the 6710 was also a much better performer than the early 6700, although it was still a rather large tractor for this power bracket. The 7710 sold very well due to the fact it had all the benefits of the 7610, but more luxury and better ergonomics.

That said, the 6610 sold well and was still a popular machine, with the column gear change being updated and improved in 1983 to make driving these models a bit easier. 

During the 1980s, the 80hp power bracket was the bestselling across all the major manufacturers and this was reflected in the good sales figures of the 6610 and, to a lesser extent, the more expensive 6710.

6610 & 6710 compared
Looking at Paul Reeve’s working examples, it is easy to see the differences between the 6610 and 6710 and, if you did not know that they were based on the same powertrain you would probably think they are two very different tractors. 

The 6610 has the lower, top-opening bonnet that was familiar to Ford tractor users since the 1960s with the new Series 10 feature of a rounded nose cone grafted on. This new nose cone not only looked different and sleeker, but it also could be lifted easily to gain access to the engine air filter. 

The bonnet extended into the cab, with the instrument panel mounted on what was basically the end of the bonnet itself, although a spacer allowed for noise reduction and a quieter experience in the cab. 

The same ‘Q’ cab was fitted to the 6710, but this was a much taller tractor, sitting higher and with a much taller bonnet. The design had been carried over from the original 700 Series with only a change of grille colour denoting its new role as part of Series 10. As had been introduced on the original 700 Series, back in 1976, the top of the bonnet was no longer easily accessible, although the side panels could be removed. 

The panels either side of the radiator were easy to remove to gain access to the air cleaner for maintenance, but it was not at all like the smaller 6610 arrangement. The radiator grille was a much larger, wrap-around affair, and the headlights were mounted externally – instead of fitted into the grille itself, as on the 6610. 

When it came to the dashboard arrangement, the 6710 was far more sophisticated than the 6610, with a proper instrument binnacle housing the dashboard, rather than the ‘end of bonnet’ style fittings on the smaller tractor. This helped give the luxury feel that these row-crop tractors generally exuded, thanks to their flat floor cab and much better positioned controls.

Both tractors were typical examples of the rest of their range, with the 6610 having several cheaper alternatives to its specification available, such as an eight-speed transmission instead of the Synchroshift, and the option of lower-profile cabs instead of the ‘Q’ cab, at less cost. The 6710, on the other hand, was already a well-specified tractor in basic format and only the ‘Q’ cab was ever offered on it, although for various export markets both it and the 6610 could be had as open platform tractors.

If I had been a tractor driver back in the early 1980s, I am pretty sure which one of these two 86hp tractors I would want to be my steed! Do not get me wrong, I have driven the 6610 all day on farms and, even though that column change takes some getting used to, I did enjoy it. But just look at the higher stance of that 6710, with its flat floor cab, easy-to-use, side-mounted gear levers, and much better all-round visibility. Given the choice, the 6710 is the one I would go for every time!

Bowing-out
In 1985, time finally ran out for the 6710. The Force II range was brought in during that year with all the Series 10 tractors being revamped in some way or another and with the Super-Q cab now replacing the original ‘Q’ version as the top-spec option. 

The 6610 duly passed into Force II guise with the new Super-Q cab and was still offered with the lower-profile cab options as before. The 6710 however, was deleted, reflecting the fact that its popularity, never that great at its height, had waned significantly as the 1980s progressed.

The 7710 carried on, being the only four-cylinder representative of what had been the 700 Series to continue into the second half of the decade. This was not that surprising really, as the 6710 had never been a popular seller. Yes, many preferred it to the awkward gear change of the 6610 and were prepared to pay the extra money to go for the luxury model, but often those purchasers would also choose to spend a bit more and get the more powerful 7710. 

The major new feature of these Force II tractors, the Super-Q cab, included gear levers positioned to the right-hand side of the driver and an almost flat floor, thereby negating the major criticisms of the original 6610 and the need to buy the 6710 instead. 

The 6710 had reigned from 1981 to 1985, and in its early guise it had first seen the light of day as the 6700 in 1976, so the model had a decent production run. Times were changing fast as the 1980s grew to a close and even the 7710 was removed from the price lists in 1989, when the Series 10 Generation III tractors arrived, its sales having been declining ever since the Force II 7610 had appeared in 1985. Even the 6610 disappeared in 1989 to make way for the 6410 and the 6810 models. 

Many of the original 6610 tractors are still in existence and even though they were less common, quite a few 6710 tractors remain in the hands of farmers and collectors, so at least today we can still compare these two 86hp tractors with very different appearances. Ford at least gave farmers the chance to choose which type of design they preferred, and that was something many competitors did not do. 

Which one of these two models would you choose?

This feature comes from the latest issue of Tractor & Machinery, and you can benefit from a money-saving subscription to this magazine simply by clicking HERE