Description And Operation; Introduction - Hydro-Gear ZT-2800 Service And Repair Manual

DESCRIPTION AND OPERATION

Introduction

The purpose of this manual is to provide in-
formation useful in servicing the Hydro-Gear
ZT-2800 , ZT-3100
® ®
Zero-Turn Transaxles. This manual includes
the general descriptions, hydraulic schematics,
technical specifications, servicing and trouble-
shooting procedures for both transaxles.
Other than recommended oil and filter changes,
the transaxle normally will not require servic-
ing during the life of the vehicle in which it is
installed. Should other servicing be required,
the exterior of the transaxle will need to be
thoroughly cleaned before beginning most
procedures. Do not wash the transaxle while
it is hot. Do not use a pressure washer to
clean the unit.
General Description
The ZT-2800, ZT-3100 and ZT-3200 are self
contained units designed for the transfer and
control of power. They provide an infinitely vari-
able speed range between zero and maximum
in both forward and reverse modes of operation.
The ZT-2800, ZT-3200 and ZT-3100 transaxle
uses a variable displacement pump with a
maximum displacement of 10cc per revolu-
tion. The transaxles use a motor with a fixed
displacement of 16cc per revolution. The vari-
able displacement pump features a trunnion
mounted swashplate with a direct-proportional
displacement control. Reversing the direction
of the swashplate reverses the flow of oil from
the pump and thus reverses the direction of the
motor output rotation. The pump and motor are
of the axial piston design and utilize spherical
nosed pistons which are held against a thrust
race by internal compression springs.
2
and ZT-3200 Integrated
TM
The transaxles are fully flooded with oil. A com-
mon external expansion tank assures the drives'
®
cool, quiet operation. An external filter on the
transaxle allows for easy oil maintenance. The
ZT-2800 is designed for both charged and
uncharged product versions. In the uncharged
consumer vehicle drive, fluid passes through
the filter by interaction of the positive head on
the fluid from a properly elevated expansion
tank and the negative pressure created at the
pump inlet during piston operation.
Hydro-Gear's patented charge configuration
is used in the ZT-3100 and ZT-3200 version.
Here, fluid is drawn from the case and through
the filter and into a fixed displacement gerotor
pump. Charge pump flow not used to feed the
low pressure side of the system is passed over
a charge relief valve and back into the transaxle
case.
The check valves in the center section are used
to control the make-up flow of the fluid to the
low pressure side of the loop.
The ZT-2800, ZT-3100 and ZT-3200 have an
internal cog style parking brake. It is essential
to fully disengage the brake prior to operation.
A cam style, block lifting bypass is utilized in
the ZT-2800, ZT-3100 and ZT-3200 to permit
moving the vehicle for a short distance at a
maximum of 2 m.p.h. (3.2 Km/h) without start-
ing the engine. The brake must be disengaged
prior to actuating the bypass mechanism.
Actuating the bypass will result in the
loss of hydrostatic braking capacity. The
machine must be stationary on a level
surface and in neutral when actuating
the bypass.
WARNING
ZT-2800 /ZT-3100
®
/ZT-3200
® TM