Zero-Turn Transaxles: EZT, ZT-2800 to ZT-5400, and Pump-and-Wheel-Motor Drives
A zero-turn steers by driving its two rear wheels at different speeds, so each wheel has its own hydrostatic drive. On most machines that drive is a Hydro-Gear transaxle, a sealed unit combining a hydraulic pump, a motor and the axle. The model number on the spec sheet, EZT, ZT-3100, ZT-5400, is one of the clearest signals of what grade of machine you are looking at, and it is the reason a Ferris 300S, IS700, ISX 2200 and ISX 3300 reach 8, 10, 10 and 12 mph. This page explains the ladder and what the largest commercial machines use instead.
What a hydrostatic transaxle does
The engine turns a belt that drives a hydraulic pump in each transaxle. Moving the lap bar tilts a swash plate in the pump, which changes how much oil it sends to the motor and in which direction. More oil is more speed; reversed flow is reverse. There are no gears to shift and no clutch, which is why a zero-turn can go from full forward to full reverse on one wheel in a single motion. The transaxle's size sets how much torque it can transmit continuously, how fast it can turn the wheel, how much heat it makes doing so, and how much weight the axle will carry.
The Hydro-Gear ladder
Hydro-Gear's model numbers rise with capacity. The EZT, also sold as the ZT-2200, is the residential unit: compact, light, usually sealed for life, and limited to about 7 mph. It is what Cub Cadet Ultima, Ariens Ikon, Toro TimeCutter and the Gravely ZT X carry. The ZT-2800 and ZT-3100 are the first serviceable grades, with an external oil filter and a published oil change interval; the ZT-3100 adds a larger axle and is the common choice on prosumer machines such as the Gravely ZT HD and the Ferris 400S.
The ZT-3200 and ZT-3400 are the light-commercial grades, rated for daily use and 10 mph. Ferris fits the ZT-3200 to the IS700 and the ZT-3400 across much of its mid range, and the Gravely Pro-Turn 152 carries ZT-3400s. Above them the ZT-4400 and ZT-5400 are the heavy commercial units: larger pumps, larger cooling fans and axles sized for 1,200 lb machines. The Ferris ISX 2200 lists ZT-4400s with 8.3 inch fans; the ISX 3300 and the Scag Cheetah II list ZT-5400s, and those are the machines rated 12 to 16 mph.
Pump and wheel motor
The alternative on large commercial mowers is to separate the pump from the motor. A pair of pumps sits under the seat, driven by the engine; a hydraulic motor bolts to each wheel; hoses connect them. Cub Cadet's Pro X 660 lists 12 cc Hydro-Gear pumps with 240 cc Parker wheel motors; Scag, Exmark, Toro and Grasshopper use the same arrangement on their heaviest machines. It costs more and adds hoses and fittings, and in return the components can be sized independently, each can be replaced on its own, and the system sheds heat better over a long day.
What the grade changes for the person mowing
Top speed is the figure the transaxle sets most directly, and it is why the table below reads like a ladder. Hill-holding and reverse pull improve with the larger units because they transmit more torque without stalling the oil flow. Serviceability is the other practical line: an EZT is generally not meant to be opened, while every grade from the ZT-2800 up has a filter and a drain, and the commercial grades have published intervals a crew can schedule around.
A fast transaxle does not make a fast mower on its own. Cutting quality at speed depends on the deck's blade tip speed and airflow, and a 10 mph machine on a residential deck will typically cut cleanly at 5 or 6. The speed figure is best read as an index of the drive's capacity rather than a cutting speed.
Reading a spec sheet
Some makers name the transaxle and some do not. Gravely, Ferris, Scag, Toro and Cub Cadet publish the model; several residential lines say only 'dual hydrostatic'. Where it is unnamed, the published top speed and the mower's weight are the next best indicators: a 7 mph, 700 lb machine is almost certainly on EZTs, and a 12 mph, 1,300 lb one is not.
What the catalogue shows
The table below groups every ride-on mower whose maker names the transaxle, with the range of published top speeds and list prices for each grade. The speed bands barely overlap, which is the cleanest confirmation that the model number means what the makers say it means.
Ride-on mowers by transaxle, with the speed each one reaches
| Models | Rated power | Top speed | List price (median) | Brands | |
|---|---|---|---|---|---|
| EZT | 44 | 18–24.5 hp | 6–7 mph | $3,899 | Ariens, Bad Boy Mowers, Cub Cadet, Ferris, Gravely +7 |
| ZT-2800 | 38 | 14.5–26 hp | 6.3–8.5 mph | $6,214 | Ariens, Bobcat, Cub Cadet, Dixie Chopper, Ferris +7 |
| ZT-3100 | 52 | 15.5–26.5 hp | 7–9.6 mph | $7,899 | Ariens, Bobcat, Cub Cadet, Dixie Chopper, Ferris +7 |
| ZT-3200 | 24 | 18.5–27 hp | 8–10 mph | $9,624 | Cub Cadet, Dixie Chopper, Ferris, Gravely, Hustler Turf |
| ZT-3400 | 25 | 18.5–38 hp | 8–10 mph | $11,349 | Bobcat, Cub Cadet, Ferris, Gravely, Hustler Turf +1 |
| ZT-3600 | 11 | 22–26 hp | 10–11 mph | — | Kubota |
| ZT-3800 | 6 | 23.5–30.5 hp | 10 mph | $13,529 | Bobcat, Ferris |
| ZT-4400 | 16 | 23–30.5 hp | 9–12 mph | $15,195 | Bobcat, Ferris, Grasshopper, Hustler Turf, Toro |
| ZT-5400 | 12 | 27–40 hp | 12–16 mph | $20,129 | Dixie Chopper, Ferris, Gravely, Hustler Turf, Scag |
| Pump and wheel motor | 69 | 15–48 hp | 7.5–16 mph | $12,899 | Bad Boy Mowers, Cub Cadet, Dixie Chopper, Ferris, Grasshopper +7 |
Grouped from the manufacturer's own drive-system wording, so a machine whose maker does not name the transaxle is not here. Speed is the published top forward speed.
The machines this page was written around
- Ferris 300S, ZT-2800
- Ferris IS700, ZT-3200
- Ferris ISX 2200, ZT-4400
- Ferris ISX 3300, ZT-5400
- Gravely ZT X 42, EZT
- Gravely ZT HD 52, ZT-3100
- Gravely Pro-Turn 152, ZT-3400
- Cub Cadet Pro X 660, pump and wheel motor
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FAQ
What is the difference between a Hydro-Gear EZT and a ZT-3100?
The EZT, or ZT-2200, is Hydro-Gear's residential transaxle: compact, usually sealed, and limited to about 7 mph. The ZT-3100 is a larger serviceable unit with an external filter, a bigger axle and more torque capacity, fitted to prosumer and light-commercial machines that reach 8 to 10 mph.
Which transaxle do commercial zero-turns use?
Light-commercial machines typically carry Hydro-Gear ZT-3200 or ZT-3400 transaxles. Heavy commercial machines carry ZT-4400 or ZT-5400 units, or a separate pump-and-wheel-motor system from Hydro-Gear and Parker, which is what the largest Scag, Exmark, Toro and Cub Cadet commercial mowers use.
Can a zero-turn transaxle be serviced?
The residential EZT is generally built as a sealed unit. From the ZT-2800 upward the transaxles have a spin-on filter and a drain, and the makers publish an oil change interval. Pump-and-wheel-motor systems have a shared reservoir and filter.
Does a faster transaxle mean a faster cut?
Not by itself. The transaxle sets how fast the wheels can turn; cut quality at speed depends on the deck. Most machines cut cleanly well below their top speed, and the published top speed is better read as a measure of the drive's capacity.
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Independent reference database. Specs compiled from manufacturer sources and normalized for comparison; verify with the manufacturer or dealer before purchase.