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Equipment Hub: Getting it into gear: Transmissions

Andy Overbay for Progressive Forage Published on 27 December 2018

In the world of farming, efficient, effective and economical have always been valuable traits welcome in just about any setting or application. When it comes to tractors and implements, those traits take on a completely new level of importance and expectations.

Selecting options for your new tractor can be a daunting task, whether you are buying a small compact tractor to use around your home and farmstead or you are more in the market for a large tractor to work up thousands of acres of cropland. While it may not be in the front of your mind when it comes to available options, selecting the correct transmission from those available for the model you set your heart on can prove to be a make-or-break decision.

Modern tractors can have several optional transmissions. Understanding what each transmission is capable of and which transmission is most suited to your needs are prized things to know.

As far as capabilities go, some of the transmissions offered in today’s machinery are really quite amazing. Let’s look at a few of these modern modes of movement with an eye on selecting your favorite.

Hydrostatic

At the base of most small tractors is a hydrostatic transmission, sometimes called an HST. Hydrostatics can be great transmissions for certain tasks that require the tractor to be at or near full throttle during the completion of the task. Examples of these tasks might include mowing, chopping corn, baling hay or any job that may require changes in speed in response to workload or terrain.

Hydrostatic transmissions function by sending hydraulic fluid under pressure through a pump, which converts this pressure to mechanical motion. The more pressure and flow the pump receives, the more motion it creates. Using either a hand lever or a two-directional foot pedal, the operator can ask the machine to go from top speed to full stop to reverse in one smooth motion.

The most obvious place to find a hydro drive is in a lawn tractor. As we described above, lawn mowing is usually done at full throttle, and the desired speed can be ramped up or down by gauging how much power is being drained or not required due to the amount of material going through the deck. We had a 125-hp hydro drive tractor for several years on the farm, and it was Dad’s favorite, especially while baling. When approaching a heavier part of the windrow, he could reduce speed, ease through that section and go right back to full speed, all while maintaining the power takeoff (PTO) speed at a constant rate.

Hydros are not without their faults and shortcomings. They can become bogged down under severe loads or while climbing slopes. They require the owner to maintain fluids at a high standard, and that fluid can be very expensive. While we are on that subject, using transmission fluid that is “cheaper” can be the most expensive lesson you ever get with a hydrostatic drive transmission.

Continuously variable

The continuously variable transmission (CVT) is an evolution of the hydrostatic drive. The major advantage (which adds to the cost of this option as well) is: The CVT transmission seeks to maintain or maximize peak engine power and efficiency at the speed selected by the operator. CVTs can be very convenient, and their operation from the driver’s seat of the tractor is very similar to a hydrostatic drive. Adding a CVT transmission can add as much as $13,000 or more to the purchase price of your new tractor.

Synchromesh

From the top-of-line options, tractors are not unlike today’s pickup trucks, where finding “four gears and a clutch” can be challenging. There are, however, gear drive models available that are similar to the tractors on which many of us learned to drive. When we look at standard-gear-drive models, many term these base models as synchromesh. So what is that?

In a synchromesh system (of which about all gear-driven vehicles are now), all of the gears in the transmission are turning at the same time and, when you engage the clutch, the shifting forks move the gear selected into a point where it is fully engaged.

These simple transmissions are not as expensive to buy and are a bit more forgiving to maintain. They offer a straightforward approach to getting power from the flywheel to the tires.

How to choose

While there are many variations of any of the transmissions we have mentioned, one bit of advice I would suggest is to talk to a trusted mechanic about what they are seeing about the serviceability of your chosen brand and the transmissions you might consider. There is no such thing as a bullet-free transmission, nor is there a way to repair a transmission inexpensively.

From experience, I also suggest thinking about how long you tend to keep a tractor. If you typically lease or trade tractors often, then a model with all the bells and whistles makes a lot of sense. If the transmission doesn’t hold up, you already have an established means to deal with it.

If you buy tractors as I do, your goal is to run them well into the time when they are identified as “classics” or even “antiques.” If that is the case, you may want to opt for the simpler of today’s modern transmissions; however, as I get older, I appreciate a tractor that can think a little bit for itself.

In the end, as I have said before, it is a lot easier to pay for the tractor and transmission you want rather than the one for which you settled.  end mark

Andy Overbay holds a Ph.D. in ag education and has more than 40 years of hands-on dairy and farming experience.

Andy Overbay
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