Lawn Tractor Transmission Types

Paul

15 years ago

Lawn Tractor Transmission Types Updated: January 2014

30-40 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.

Because the transmissions were so heavy there was a lot of weight on the rear wheels and you could pull just about anything with them including moldboard plows. Because they were so heavily built they were also very heavy and would put grooves in your lawn if you mowed the same way more than once or twice.

Over time we asked for lawn tractors that mowed faster, turned better and didn’t cause so much damage. We no longer had the huge Victory Gardens that required plowing with the garden tractor and if we did we used rototillers instead. So the manufactures listened and changed from the heavy, cumbersome tractors to lightweight tractors that mowed well, mowed faster, turned easier and didn’t cause damage to our lawns.

Seven Types Of Transmissions:

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.

Gear Transmissions

Twenty years ago the gear drive transmission was the most popular but today automatic hydrostatic and automatic CVT 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. They use and inline gear selector instead of the old H-pattern. 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.

Some manufactures have a shift-on-the-go transmission. This is sometimes listed as a manual transmission but it is actually a CVT. These transmissions are found on the least expensive lawn tractors and are usually listed as 6 or 7 speed.

Friction Disk Transmissions

This is actually the transmission of choice for snow blowers but there are a few mowers like the Snapper Rear Engine Rider that still 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

John Deere originally used a CVT in conjunction with a manual transmission on the Model 110. Now days, CVT’s have now matured to the point where you find them in cars, snowmobiles, snow blowers and even heavy-duty farm tractors. There are very few parts that wear in these transmissions and the recently introduced Element V from General Transmissions for your yard tractor is now stronger and requires less worry than all the hydrostatic transmissions. CVT’s for lawn tractors essentially a belt and variable pulley system similar to the drive system in a snowmobile or mini-bike.

I predict that CVT transmissions will replace most of the hydrostatic transmissions within the next 5 years.

MTD is using this on many 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.

The Element V from General Transmissions is another CVT that you will now find in Yard Tractors. This transmission is tougher, lighter weight and takes less power than the very popular Tuff Torq K46 and Hydro-Gear T2 hydrostatic transmissions. In fact the RS 800 Element V transmission is power rated very close to the most popular garden tractor transmission, the Hydro-Gear G730. These transmissions are very easy to use. Either a fender mounted lever or foot control varies the speed and direction just like the hydro transmission you are used to. These transmissions do not need maintenance and I expect them to last the life of the mower.

To see how tough these new transmissions really are check out spot 1:27 in the next video!

There is one other form of CVT that has the possibility of also replacing the hydrostatic transmisson. Fallbrook has announced a commercial partnership with Hydro-Gear to bring NuVinci technology to the lawn & garden market. Instead of a variable pulley system uses 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.

Hydrostatic

The most common transmission for lawn tractors today is an internal pump and motor drive system called the hydrostatic transmission. There are two types of these transmissions used in Lawn & Garden equipment, hydrostatic enclosed single and hydrostatic enclosed dual. Everything is enclosed in an aluminum housing. Hydrostatic transmissions are more expensive than mechanical transmissions but they are much easier to use.

Hydrostatic – Enclosed Single

Most lawn tractors, yard tractors, garden tractors and estate tractors in the last 20 years 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 designed for mowing and light hauling. A garden tractor transmission is heavier duty and can be used not only for mowing but ground engaging tasks like pulling a DR Power Grader/a>. Hydrostatic transmissions are very easy to use. Either a fender mounted lever or foot control varies the speed and direction.

The residential models you find on today’s lawn tractors are sealed units and are not serviceable by you. Most of the transmissions have to removed from the tractor for any repairs. As an owner the only maintenance you have to do is periodically clean the outside of the case with a leaf blower or garden hose. They are designed to give you hundreds of hours 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 hydrostatic 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.

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. If you want to pull a leaf vacumn or move dirt in your yard cart this is not the transmission for you.

https://www.youtube.com/watch?v=7-x_gCG9llo

Most of these transmissions are controlled by individual levers called lap bars that sit in front of you. This type of transmission takes practice to keep the tires from digging into your lawn but 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.)

Hydrostatic – Pump & Motor

The more expensive commercial zero-turn mowers, stand-ons, and some golf course mowers use a separate variable displacement 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.