Lawn Tractor Transmission Types Updated: March 2013
30 years ago gear drive transmissions were about the only transmission available for your tractor. They were built just like the transmissions in a Model A Ford or a 1953 Farmall tractor. Big, strong gears. Heavy axles and cast housings. They didn’t break but they were hard to use. You had to stop the tractor to change gears and most of the time you had to wiggle the tractor to move the shifter from one gear to another. The L&G purists pine for the “good old days” but I’m glad they are gone.
There are now seven types of transmission found in today’s lawn tractors and zero turns. They are gear, friction disk, automatic or CVT, hydrostatic, pump/motor, electric and hybrid. I’ll spend a few paragraphs going through each type so you have a better idea of the best type for you. I am not going into the details of how each one works. Just Google the transmission type and you can read to your heart’s content.
Ten years ago the gear drive transmission was the most popular but today hydrostatic and automatic transmissions have replaced them in popularity. Often called Manual transmissions this type uses a series of gears to change the ground speed of your tractor. These transmissions are not like the older styles though. They shift better, are much, much lighter and easier to use. The biggest downfall of this type of transmission is you have to stop the tractor to shift to a different speed (range). This makes them harder to use when you have a lot of garden beds and landscape features to go around.
To drive the tractor you must push in on the clutch, shift the transmission to the gear you want to use, release the clutch, and hang on. This is a dependable transmission that will give you years of service.
This is actually the transmission of choice for snow blowers but there are a few mowers like the Snapper Rear Engine Rider that use this trans. It is a good, dependable transmission when used properly. It uses a friction wheel and disk to change the forward speed of your rider. Don’t use this transmission to pull heavy loads…you will tear up the friction wheel.
You can shift-on-the-go with some models but to get the longest life most brands suggest you push down on the clutch/brake pedal and then shift to the speed you want.
Automatic or CVT
This is essentially a belt and variable pulley system similar to the drive system in a snowmobile. John Deere originally used this in conjunction with a manual transmission on the Model 110. Now days, MTD is using this on most of it’s least expensive lawn tractors. Using one is very much like driving your car. Put the lever on the fender in F and then press the right foot pedal. The farther you push the pedal the faster you go. To go in reverse put the fender lever in R and press on the right foot pedal.
This trans is designed to mow lawns and is not designed to pull heavy loads. Some of the brands have confused the issue by calling their inexpensive hydrostatic trans an “automatic” so if you are unsure ask me in the comments below.
This is a dependable transmission that will give you years of service for flat lawns and pulling very light loads.
The automatic mentioned above and the hydrostatic below are forms of CVT’s. But technology is changing and now days CVT means a variable disk or ball/disk system. This is the transmission of the future because it uses fewer moving parts than a gear trans, can pull heavier loads than an automatic and uses less oil than a hydrostatic. At this point in time though they are not yet cost effective for lawn tractor applications. MTD tried using the dual IVT Infinitrak in the Cub Cadet and Craftsman Revolution but consumers were not ready to spend the extra money to own this type of transmission. New Holland is using these effectively in their 50 hp and larger tractors. Fallbrook has announced a commercial partnership with Hydro-Gear to bring NuVinci technology to the lawn & garden market. I can’t wait!
These transmissions are very easy to use. Either a fender mounted lever or foot control varies the speed and direction.
The most common transmission for lawn tractors today is a form of continuously variable transmission called the hydrostatic transmission. These transmissions take several forms, from pumps driving separate motors, which may incorporate a gear reduction, to fully integrated (enclosed) units containing a pump, motor and gear reduction all in one aluminum housing. Hydrostatic transmissions are more expensive than mechanical transmissions but they are easier to use and can transmit greater torque to the wheels as compared to a typical mechanical transmission.
Hydrostatic - Enclosed Single
These transmissions are very easy to use. Either a fender mounted lever or foot control varies the speed and direction. Most lawn tractors, yard tractors, garden tractors and estate tractors today have an aluminum housing and inside that housing is the pump, motor, differential and drive axle. These transmissions are sized to the mower application so a lawn tractor trans is for mowing and a garden tractor transmission is heavier duty and can be used for many heavy duty tasks. The residential models you find on today’s lawn tractors never need maintenance, just a good cleaning once in a while of the outside case. They are not serviceable by you but are designed to give you years of service for normal use. The garden tractor and estate tractor hydrostatic transmissions are heavier and built to handle heavy loads and ground engaging attachments. Most of the transmissions in lawn tractors do not have posi-traction or differential lock.
These transmissions are very easy to use. Either a fender mounted lever or foot control varies the speed and direction. The pedal on the left side of the tractor is the parking brake. You do not need to depress that pedal to shift the tractor. The forward and reverse is controlled by either a lever on the right fender or two pedals on the right side floorboard. To go forward push the fender lever forward or press on the large pedal on the floor board. To stop the tractor pull the lever back to the middle position or lift your foot off the pedal. To back the tractor up pull the fender lever to the rear or press the small pedal on the floorboard.
On the fender mounted control you HAVE to move the lever to the middle to stop your tractor. It will not go to neutral by itself like the foot controls.
One of the big problems with hydrostatic transmissions is owners have a tendency to go faster than the lawn mower deck will actually mow well at. Craftsman introduced for this year the LT2500 lawn tractor that has a notch in the fender control that shows where the normal mowing speed is. I’ll go through each type below.
Hydrostatic - Enclosed Dual
Two hydrostatic transmissions are mounted side-by-side in the residential zero turns. Each trans controls a separate rear wheel. That is the primary reason why zero-turn mowers cost more than the lawn tractors. Again these trans are designed for the application and most are not designed to pull loads, just mow and bag.
Most of these transmissions are controlled by individual levers that sit in front of you. With a little practice these are very easy to use. A large lever on each side of the seat controls that side transmission. To go forward push on BOTH levers. To stop, pull them back. (The easiest way to explain how to drive a two-lever zero turn mower is to use a shopping cart as an example. With the mower turned off sit on the seat and put your hands on the two large levers in front of you. Close you eyes and pretend you are gripping a shopping cart. What do you do to move a shopping cart forward? Right, you push on the handle. To back up? Right, you pull back on the handle. To go left? To go right? Correct, you PUSH the handle in the direction you want to turn the cart. Two lever zero turns work the same way. Instead of one bar like a shopping cart, the bar is split in two and you move each side to make it move.) This type of transmission takes practice to keep the tires from digging into your lawn.
Hydrostatic - Pump & Motor
The more expensive commercial zero-turn mowers, stand-ons, and some golf course mowers use a separate variable pump near the gas engine connected to the wheel motors with hydraulic hose or metal lines. These are usually cast iron for long life and durability. A few of the high-end commercial mowers are now using enclosed cast iron hydros.
Electric drive systems are found in the mowers like the Hustler Zeon and consist of batteries, electronic controllers and electric motors. The huge advantage is the current designs use no belts filters and fluids so they take less yearly maintenance. If you want green technology, no gas engine emissions and 30% less noise on your lawn this is an up and coming alternative to gas powered lawn mowers. You charge the mower using normal household current. They are currently limited by battery technology and battery price.
The Lowes Raven used a hybrid drive system. A smaller gas engine (13 hp) charges batteries. These batteries then are used to power the lawn mower just like an all electric lawn mower. This technology is beneficial because it uses less fuel to mow your lawn and is quieter than using lawn tractors with larger engines. The technology is sound but the actual implementation is not quite ready for the masses. Give this a couple of years to work the bugs out in the manufacturing and it will be a great alternative to the gas powered lawn tractor.
Electrics are coming and I feel in the next 5 years you will see affordable homeowner versions. These machines are not lawn tractors with electric motors replacing the gas but true state of the art electric vehicles. There are already commercial models that will mow all day long on a single charge.