John Deere 9880 STS deserves its place among the ranks of the top performance used combines, alongside the likes of the New Holland CR980 and Claas Lexion 480. (Editor’s note: The 9880 STS is a European model, roughly equivalent to the brand new 9870 STS launched in North America just last year.) Indeed, raw spec of the first STS models still makes for some impressive reading: 465 hp, 12.5-litre PowerTech engine with extra power, 300-plus-bushel grain tank. When operating at max output, this is some grain gobbler.
At the heart of the big green machine is its STS single-tine separation system. According to Deere, the single STS rotor is designed to offer “higher throughputs, lower power and fuel consumption, and quality straw with less damage than that inflicted by other conventional rotary combine designs.” Quite a set of manufacturer claims.
Fast forward to the 2008 model season, and the STS harvester design has seen a degree of evolution, even though the basics remain largely the same. From a used buyer’s perspective this is welcome news. It should mean that an early STS will give little away to a newer sibling.
What to look for
Start by running a critical eye over the machine’s overall appearance. Even if a combine has not been cleaned, it should be possible to peek through the grime to make a fair judgement on the combine’s overall condition. It may just take a little more time to check for physical damage and signs of neglect.
When cleaned up, STS combines typically hide their hours well, so bear this in mind when
inspecting a high-hour machine.
Use the header as the kick-off point for detailed checks. The 600R Series platforms come in 620R, 622R, 625R and 630R versions. The last two digits refer to the width in feet, the 30-foot 630R typically becoming the default STS choice for most users.
As an aside, the crop knife position on 600R headers can be adjusted to bring STS’s knife back so that it works closer to the auger. This is ideal when operating in laid crops. The knife adjustment is done manually, however, so that altering the knife position will take two to three hours; most operators run with their knife in the front position for oilseed rape and rear position for cereals and pulses.
On all designs, look out for physical damage to the auger from stones, and check the fingers are all present. Reel batons should be straight; the reel is not prone to sagging even on the 630R. Inspect for wear in the cutterbar, and don’t forget the spare knife. The latter is made up from sections, so confirm it is the full length.
The header tends not to need any lifters, although it does make sense to have a set all the same.
The header driveline is pretty tough, the only likely modification being the inclusion of an additional idler pulley to help tension the wobble box’s drive belt. This belt could be tricky to tension on headers made up until 2004.
The auger’s alloy support brackets are designed to give way should the auger ingest a large lump. This system protects the header, so do not be alarmed to see a replacement fitted. These supports are pretty tough, but if one does break it will cost around 100 ($200 to $250) in parts to replace. Do not overlook the header trailer, ensuring the header clamps are not damaged.
Moving on to the feed elevator, assess the housing’s condition. The elevator raddle chain typically lasts for 2,000 hours. Check for excess wear and bent slats, as outofshape slats increase wear on the chain.
Where there are any doubts about the elevator chain, budget to replace it.
In terms of drive, the header drive chain tends to run a bit slack, so ensure that the chain’s plastic channel guides are in sound order. These chains should last for around 1,500 hours.
It is now time to crawl under the elevator to look at the F. A. S. T pre-accelerator unit and the stone trap. In broad outline, the pre-accelerator is a horizontal rotor that accelerates the progress of the crop mat between the end of the elevator and the main rotor.
Any rocks/stones within the mat tend to be drawn out by the pre-accelerator and forced into the stone trap. A degree of light stone damage on the rotor’s ten serrated “wings” is relatively normal, but
heavy damage may upset rotor balance.
There are two speed settings offered by the accelerator, the slower speed being selected for pulse crops. Check that this speed adjustment can be made. The stone trap flap is opened via a single lever; open it up and see if it has been emptied.
Next take a look at the fan speed variator drive and the fan itself. The fan bearings need a shot of grease once a year and last well, but still check for any play.
Switching attention to the returns and main elevators, inspect these items for any paddle damage. If the chains are at the end of their travel, see if there is a half-link remaining in the run. Included from new to allow the chains to be easily shortened when the initial adjustment travel is taken up, a missing link shows the first level of wear has already been used. If there is no link to remove and the chains are near the end of their adjustment, budget in some additional funds to renew the chain.
The rotor drive belt should typically last around a couple of seasons, with a new one costing about 500 ($1,000). Thankfully, it is simple to renew. Size of the rotor drive pulley was increased back in ‘04, but the earlier design is not liable to problems.
Although the rotor works hard, any issues with the drive can usually be traced back to the operator trying to drive it too fast in difficult harvesting conditions.
It is always dangerous to generalize, yet users suggest that the rotor speed can be dropped down to as low as 265 rpm in
tough going, the concave setting also needing to be adjusted.
Opening the concave up to a generous 20 mm clearance is perfectly acceptable when matched to
With a little care and some thorough research, it should be possible to pick up a value-for-money machine that’s capable of high outputs
the right rotor speed for the job.
The front of the STS’s rotor works the hardest, so check in this region first. The rotor housing concave and separator grates are enclosed by easily-removed covers, and closer inspection is also not too awkward because each of the grates is secured by just the four small bolts. In other words, there’s no excuse for not carrying out a thorough inspection of the rotor.
If a paddle along the rotor is damaged, it should be replaced as
a pair with its opposite number — to ensure the rotor balance is not upset. When run up, the rotor should spin smoothly. If there is any roughness or vibration, seek advice. In most instances the cause can be swiftly remedied, but it can take time to identify what is causing the problem.
The concave clearance is set via a pair of adjustable metal rods working from a motor driven shaft. These metal rods are designed so that they will snap if an oversized wedge of material enters the rotor, this helping to prevent a difficult-to-clear blockage. On combines built up until ‘04, these rods were M12 in size. This spec subsequently increased to a heavier M16 gauge, with the latter available as a direct retrofit. Tip: It’s worth carrying a couple of spare M16s in the combine cab.
The cleaning area is pretty straightforward to examine, as long as the light lens that illuminates the cleaning bay isn’t filthy. Assess the sieves for damage and ensure all the adjustments can be made. The Dyna-Flo system common to all STS models was changed to Dyno-Flo II from the 2005 model year, a major difference being that “II” includes electronic sieve adjustment.
Climbing up into the engine bay, the key points to concentrate on are that everything is in neat and tidy order. Inspect the grain tank covers, making sure that they open and close properly. Keep an eye out for damage, typically caused by running under a tree, or from someone walking over them. The folding system design was altered in 2006. Changes were also made to the fuel tank, which was enlarged to 1,145 litres, and to the battery position.
It is possible to peer down onto the variator pulleys from the engine bay. The belt can be adjusted to accommodate wear, but it will need renewing when the spacing at the bottom of the pulleys is less than eight mm (5/16 inch) across with the slowest speed set and at the limit of adjustment.
Finally, check the unload auger for dents and repairs.
In broad outline, that just about covers the main check points. John Deere makes looking over the STS a relatively painless process, the harvester benefitting from wide opening access panels and easy-to-get-at major components. Most routine servicing is straightforward too, a point to remember when trying to reduce overall combining costs.
The STS operators we spoke to all praised their harvesters’ performance, simplicity of maintenance and smooth operation. With a little care and some thorough research, it should be possible to pick up a value-for-money machine that’s capable of high outputs. Given the support of a strong local John Deere dealer, a second-hand STS certainly has its attractions.
James de Havilland writes for Profimagazine. For more on this European farm equipment publication, visit the website at www.profi.com