Cub Cadet BDU-10/21 - Manual (Page 3)

BDU-10/21
BDU-10/21
The fluid supply for the BDU-10L/21L transmission is
contained in an external reservoir and passes through an
external filter prior to entering the transmission and feeding
the fixed displacement gerotor charge pump. Excess fluid
in the charge circuit is discharged over the charge relief
valve back to the charge pump inlet. Constant flow across
a small fixed orifice connecting the charge circuit to the
transmission housing supplements the cooling flow.
The BDU-10S transmission has a self-contained fluid
supply and an integral filter. The fluid is forced through the
filter by positive “head” on the fluid in the housing/reservoir
with an assist by the negative pressure created in the pump
pistons as they operate.
Charge check valves in the center section are used to
control the makeup flow of fluid to the low pressure side of
the loop.
A spool type bypass valve is utilized in the transmission to
permit moving the vehicle for short distances at low speeds
(2mph) (3.2 km/hr) without starting the engine.
Introduction/General Description
Page 3
Introduction
The purpose of this manual is to provide information useful
in servicing the BDU Hydrostatic Transmission product
line. This manual includes unit and component descrip-
tion, troubleshooting, maintenance, and repair proce-
dures.
A transmission normally will not require servicing, other
than the vehicle manufacturer’s recommended fluid and
filter changes during the life of the vehicle in which it is
installed. Should other servicing be required, the unit must
be removed from its installed location and thoroughly
cleaned before beginning most procedures.
General Description
The BDU Hydrostatic Transmission is designed for the
transfer and control of power. It provides an infinitely
variable speed range between zero and maximum in both
forward and reverse modes of operation. The BDU trans-
mission can be mounted to a variety of transaxles including
most HYDRO-GEAR models.
The BDU transmission is a “U” style transmission with a
variable displacement pump and a fixed displacement
motor. The variable displacement pump features a cradle
swashplate with a direct-proportional displacement con-
trol. Reversing the direction of tilt of the swashplate
reverses the flow of oil from the pump and thus reverses the
direction of the motor output rotation. The fixed displace-
ment motor uses a fixed swashplate. 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.
BDU-10L Transmission