What Transmission?
Tip 0014

Tractors are driven differently than an automobile. Automobiles typically have three to five gears and can exceed 60 mph. Tractors may have up to 24 gears and a top speed of 15 mph. In an automobile subtle changes in speed are made by changing the engine speed. Tractors, on the other hand, when operating a PTO driven implement, are run at a fixed engine speed and the gears are shifted to change ground speed. Often the tractor's performance is greatly impacted by the transmission choice you make.

The basic 8X2, 6X2 or 9X3 transmission is the least expensive option. This transmission is much like a standard car transmission. 3 or 4 forward speeds, 1 reverse and 2 or 3 ranges (high, low, medium). These transmissions are usually not synchronized which may make speed changes difficult. You pick a gear, let the clutch out and go. Shifting to reverse is done at a full stop. Reverse is often at a different speed than forward. For traditional fieldwork these transmissions are inexpensive and reliable.

Shuttle shift transmissions have been used for many years on tractor loaders. The reverse mechanism may be mechanical or hydraulic. Mechanical shuttles require using the clutch to change direction, but they are synchronized. Hydraulic shuttles can be shifted without using the clutch. Either way, these transmissions allow the operator to change directions with out stopping. They allow for similar speeds in forward and reverse and increase productivity with a loader.

Kubota has taken the shuttle shift to a new level with the Glide Shift Transmission (GST). The GST allows the operator to shift up and down through all of the speeds without clutching and to shift from forward to reverse with out stopping or clutching. This is a mechanical transmission with an automatic clutch. The Glide Shift Transmission provides the PTO hp and positive ground speed of a gear drive with the ease of changing speed and direction associated with a hydrostatic..

Hydrostatic transmissions are becoming the popular choice for compact tractors. The foot pedal(s) allows the operator to run the loader and three-point hitch with the right hand, steer with the left hand and control speed and direction with their foot. This method of operation is faster and less fatiguing than having to shift with one or both hands, clutch with the left leg and run all the other controls. This transmission is similar in operation to an automatic transmission in your car. You can change speed and drink a cup of coffee!

For 2007 Kubota has gone to the next level in hydrostatic technology. The Grand L-40 series is now equipped with HST Plus. The HST Plus transmission is now electronically controlled via an ECU. The primary advantage of this system is ease of use for the operator eliminating the potential drawbacks of other hydrostats. This is accomplished with four new functions. These functions may be used in any combination or turned off to suit the operator.

First is HST Response Control. This function is controlled by a dial on the dashboard to customize the "feel" of the transmission to the task or operator preference.

Second is Hydro Dual Speed (H-DS). H-DS is a 2-stage HST motor that is controlled by a lever on the steering column. Within each of the three manually shifted ranges there is a Hi and Lo controlled by the HDS. Thus, the operator can shift down when coming into a hill or when using the loader and back into high when speed is needed. Shifting into Lo will increase torque by 60% and reduce travel speed by 40%.

Third is Load Sensing. This function uses Stall Guard and Auto H-DS. Stall guard overrides the HST foot pedal if a heavy load is encountered. Using a traditional HST, when going up hill or into a pile with the loader, if the operator pushed the pedal to the floor the tractor could stall. With stall guard enabled the transmission automatically reduces the amount of oil being pumped through the transmission and avoids stalling the engine. Auto H-DS will automatically shift the 2-stage HST up and down depending upon the load.

Finally the L-40 is equipped with Auto Throttle Advance. When Auto Throttle Advance is engaged, pressing the HST pedal will automatically advance engine rpm's. Letting off the pedal will automatically reduce the engine rpm's to the hand throttle setting. Using these features will maximize productivity and ease of use for even the most inexperienced operator.

Larger tractors typically offer more transmission choices than their smaller siblings. What work and what budget you are working with will often be the best guide of which transmission to choose. However the timesavings of a shuttle or a hydrostatic transmission may offset the extra purchase price.

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