To clutch or not to clutch? That is the Transmission.

posted on Wednesday, October 3, 2018 in United Ag & Turf News


You have the land, the motivation, and the direction.  You have made the decision you need or want a tractor. A tractor is a machine created to deliver high tractive efforts at reduced speeds.  Tractors are used for power during ground work.

Now it is time to decide how you need the tractor to function and deliver power to the ground.  Gear driven, Gear Driven with PowReverser™, Hydrostatic, Power Steering, Cruise Control, 2WD, MFWD, 4WD, Spur Final Drive, Planetary Final Drive, Wet Clutch or Dry Clutch. Why is a transmission so complicated?

Transmission (noun)

transmission | \trans(t)s-mi-shen  

An assembly of parts including the speed-changing gears and the driveshaft by which power is transmitted from an engine to the live axle. 

When choosing your transmission options, the life of the unit, the maintenance cost, and value of functionality must be considered.  The choices are endless and could take days to explain.  Here a few simple ways to view the options. 

Manually gear driven or hydrostatic? Gears are tough and do not require a lot of other components to function such as special fluid or filters.  Hydrostatic does not require clutching, quickly changes speeds and is user friendly. Simply put a clutch – actuated or fully automated gear box is chosen by price and convenience.  The manually driven will require less cost upfront and more effort on the driver.  The hydrostatic option is costlier but decreases effort on the operator.

2WD, MFWD or 4WD? A 2WD will receive power from the drivetrain equally to two wheels.  2WD is cost effective and works well for general use in dry conditions.  MFWD is selectable between two-wheel drive and all-wheel drive and is specifically geared for the front-end size difference. MFWD is often the choice for compact and utility size tractors for frequent loader applications for greater traction control.  MFWD has increased traction for reducing ground slippage.  A 4WD tractor is always engaged, produces power to four equally sized tires and often found on large row crop tractors and earth moving tractors.   

Final drive options?  A differential is used to avoid slipping when wheels are turning at different speeds caused by loss of friction.  The differential unit houses the gears which work together to create motion.  Due to the differential the outer wheel, when turning, may run at a different speed than the inner wheel creating more traction. The final drive is an added component beyond the differential.  The need for a final drive on a tractor is due to additional slippage a tractor may incur because of varying ground conditions where less friction occurs. With the additional gear the torque increases. A spur gear final drive is a simple design but bulky, efficient but noisy. Spur gears are lower cost.  A planetary gear final drive is a complex component with higher efficiency and reduced noise.  Planetary gears are costlier due to complexity. 

Dry clutch or wet clutch? Dry clutches are cheaper and easily changed but wet clutches have a longer life. 

With so many options to choose from one would be well advised to utilize their resources during the decision process and be clear about what task you envision doing. Talk with one of our friendly staff, they are the folks who will help you with your equipment questions, help you choose the right equipment for your land & tasks and how to maximize its potential.

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