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On-test: Latest John Deere T Series combine

With a heavy host of updates including increased threshing capacity and improved operator convenience, John Deere has revised its T Series straw walker combines. Richard Bradley finds out more with a test drive.

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The T670 is John Deere’s largest capacity straw walker combine.

Focusing on boosting harvesting capacity, improving crop flow and meeting Stage 4 emissions regulations, John Deere has updated its high capacity straw walker combines.

John Deere's combine range at a glance

Straw Walkers:

  • W Series - maximum 210-380hp, grain tank size 5,200-9,000 litres (optional)
  • T Series - maximum 300-450hp, grain tank size 8,000-11,000 litres

Rotary threshing:

  • S Series - maximum 380-620hp, grain tank size 10,600-14,100 litres

The T Series sits between the manufacturer’s smaller W Series straw walkers and larger rotary threshing S Series combines. In total, four models are available, with maximum power ranging from 300-449hp. A number of drive and running gear options are also available, including the option of tyres or tracks with 40kph road travel.

To see what impact the updates have on the T Series, we tried out the largest model in the range, a T670i, in East Lothian, Scotland, cutting some of the region’s first wheat

Feeder and threshing system

Up front, feeder house chains have moved inwards and slats widened to ensure even crop flows right up to the edges of the feeder housing. Its slip clutch is now uprated from 600Nm to 900Nm to keep crop flowing into the combine.

For convenience, the booster bar on the main concave can now be swung in and out on a ratchet system to increase the aggressiveness of the threshing process. Previously this had to be removed and replaced to get the same effect, so it should save time when conditions and crops change.

Aiming to increase machine throughput, concave wrap angle round the main threshing drum has increased by eight degrees. To accommodate this, the overshot beater and rear separator drum have increased in size to 500mm and 800mm respectively. The manufacturer says along with the new open wire design concave, this gives extra threshing capacity with a 21 per cent increase in active separation area. Despite this, John Deere says crop flow remains smooth and straw quality is maintained.

Swapping between crops has also been made easier. Header side knives can be installed and removed quickly. Drive is through a mechanical connection from the cutter bar and a simple locking mechanism holds the knives in place. Also, quick adjustment of the rear separator drum concave is done via two handles, now located on one side of the combine.

Crop separation and residue management

Thanks to an aluminium construction, the manufacturer’s new DynaFlo Plus cleaning shoe is claimed to give a 41 per cent increase in sieve surface area, while reducing its weight.


A redesigned fan is also featured, aimed to improve airflow. The manufacturer says these features reduce the cleaning shoe sensitivity and make it easier to adjust to reduce tailing losses.

To reduce downtime, unloading rates get an increase of 30 per cent to 125 litres per second. A 34hp boost is provided when unloading on the move, to maintain efficiency while harvesting.

At the rear of the combine the straw chopping unit features a greater wrap angle to give more consistent chopping. Vanes effectively spread the chopped straw across the full nine-metre header width. Standard chopper unit features 52 rotating knives, or a 96 knife unit can be specified.

Adjustments to static knives have to be done manually with tools. Adjusting the spreading vanes also requires tools at the rear. However, in-cab adjustment is optional and there is a hydraulic system for compensating crosswinds as standard.


Changing between leaving a swath and chopping straw is simple, but still requires lever pulling at the rear. In-cab control would be a handy feature.

Engine and maintenance

Meeting the latest Stage 4 emission regulations, Deere has fitted its new PowerTech engine, with diesel particulate filtration and selective catalytic reduction using diesel exhaust fluid.

Engine air is now drawn from behind the radiator grille into a new cyclone technology pre-cleaner before entering the filter. Deere says this system should reduce the need for regular filter cleaning, aiming to make filters a fit and forget item until the next scheduled service.

Engine bay access has been improved thanks to a new swingout platform with removable ladder. Gas struts make it easy to open and shut the large panels, which lock back with a sprung latch.

Previously only available as a dealer-fitted option, an air compressor with 60 litre reservoir can now be factory fitted. This option comes with a lance, 10m hose and three connection points, with one in the engine bay and one on each side of the combine, meaning you can reach the entire machine.

Up to four cameras can also be fitted, displaying on the manufacturer’s CommandCenter terminal. We found the camera overlooking the grain tank useful when caught short of trailer drivers. The fourth audible warning of ‘the grain tank is full’ really does mean it is full.

Transmission and chassis

Electric shifting of the combine’s three-speed transmission is standard on the three larger T Series models, as is 40kph road travel speed. Shod with 900mm wide tyres, a six walker T670i combine measures less than 4m wide.


Fitting the manufacturer’s track units brings this down to less than 3.5m.

The manufacturer says the chassis and rear axle have been strengthened, and to prevent chaff build up and keep the machine cleaner round the back end, chamfers and fillets have been put in every possible joint.

Increased by 18 per cent, steering angle with the manufacturer’s new four-wheel drive X-Traction rear axle addresses previous user comments of turning circle issues. A single drive motor is mounted in the centre of the axle, with a limited slip differential providing the final drive to each wheel.


The manufacturer says its traction control system, fitted in combination with its ProDrive step-less transmission and X-Traction axle, allows effective power distribution between the front and rear axles.

FG Verdict

Both inexperienced and regular combine operators will appreciate the features on Deere’s latest T Series combines.

For the relatively inexperienced operators, the ability to quickly set the machine for harvesting is a handy feature. By entering limited information, the machine can set up sieves, fan speed and adjust the header, with only minor adjustments needed to optimise performance.

Regular operators will appreciate the improved engine access, no daily greasing points, and blockage detection. This will give the operator confidence to push on without the same fear of damaging the machine.

Changing between chopping straw and leaving in a swath from the comfort of the cab would be a welcome addition, as would the ability to adjust static knives in-cab, as the less effort required to adjust something, the more likely it is to be done to get optimum performance.

Despite the slightly chewy Scottish wheat, the updated threshing system allowed forward speeds of 6kph with a 9m header. In-cab monitors showed harvesting rates of 12 tonnes per hectare (5t/acre) without too much effort from the Deere’s twin-turbo engine.

T670i ProDrive HillMaster specifications

  • Engine: Six-cylinder, nine-litre, Stage 4-compliant using diesel exhaust fluid
  • Rated power: 392hp at 2,200rpm
  • Maximum power: 449hp
  • Transmission: Variable 0-40kph
  • Active separation area: 4sq.m
  • Straw walker area: 5.8sq.m
  • Cleaning shoe area: 6.3sq.m
  • Grain tank volume: 11,000 litres
  • Auger unloading speed: 125 litres per second
  • Retail price: £406,835 as tested
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