General - Simplicity 1691682 Service & Repair Manual

SAUER-SUNDSTRAND HYDROSTAT-
IC DRIVE UNIT BDU-10L-258

General

The Sauer-Sundstrand hydrostatic drive unit, BDU-10L is
a self contained hydrostatic pump and drive motor
designed to be used with the Hydro Gear Model 216-
3010 heavy-duty differential.
The hydrostatic drive unit contains a variable displace-
ment pump and a fixed displacement motor. Both used
axial pistons and spherical nosed pistons. The fluid sup-
ply is contained in the transaxle case and passes
through a filter before being delivered to the pump. The
10L has a fixed displacement gerotor charge pump sup-
pling a constant closed loop of fluid to the main pump.
Figure D-1. Sauer-Sundstrand Hydrostatic Drive Unit BDU-10L
IMPORTANT: Cleanliness is a primary means of
assuring satisfactory life on new or repaired units.
Cleaning parts by using a solvent wash and air dry-
ing is usually adequate. As with any precision equip-
ment, all parts must be kept free of foreign materials
and chemicals.
7D Sauer-Sundstrand BDU-10L-258
Fluid required to replenish the closed loop flows either
into the transmission or pump housing through a cooling
orifice, or back to the charge pump inlet through the
charge pressure relief valve.
The parts manual exploded view is contained in this sec-
tion to show the service parts and kits available for ser-
vice repair. Most internal components are not service-
able except through a Sauer-Sundstrand Authorized
Service Center.
Do not attempt repairs on pumps without a thorough
knowledge of hydrostatic repair.
• Protect all exposed sealing surfaces and open cavities
from damage and foreign material.
• Prior to removing and disassembling transaxle, the
tractor should be steam cleaned or blown with com-
pressed air before beginning any repairs.
• It is recommended that all seals be replaced before
transaxle is reassembled. Lightly lubricate all seals
with a clean petroleum jelly prior to assembly.
• After transaxle is removed from the tractor, remove all
external components such as the brake arm, brake
actuating pins, control arm, input pulley, and frame
mounting hardware before separating case halves.
7 - 47
7 Transmission Repair