BDU-10/21 Hydrostatic Transmissions Service and Repair Manual BLN-50327 January 2009
BDU-10/21 Table of Contents Table of Contents Description Page Introduction ...................................................................................................... 3 General Description ....................................................................................... 3-5 Fluids............................................................................................................... 6 Safety Precautions ..............................................................................
Introduction/General Description BDU-10/21 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 description, troubleshooting, maintenance, and repair procedures. 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.
BDU-10/21 General Description The BDU-21L transmission offers an optional Implement (auxiliary) pump. The auxiliary circuit provides a rated flow of 1.5 gpm (5.67 l/min) and 500 PSI (34.5 bar) operating pressure at a 3200 RPM pump speed. Fluid from the charge pump flows first to the implement control valve, then to the charge relief valve and charge check valves in the center section. This requires an “open center” type control valve to allow fluid flow to return to the transmission.
General Description BDU-10/21 BDU-10L/21L Hydrostatic Flow Illustration BDU-21L/A Hydrostatic Flow Illustration BDU-10/21 Page 5
BDU-10/21 Maintenance Fluids Maintenance The fluids used in HYDRO-GEAR products have been carefully selected, and only equivalent, or better products should be substituted. Typically, an engine oil with a minimum rating of 9.0 cSt (55 SUS) at 230°F (110°C) and an API classification of SJ/ CD is recommended. A 20W-50 engine oil has been selected for use by the factory and is recommended for normal operating temperatures.
Troubleshooting Diagram BDU-10/21 OPERATES IN ONE DIRECTION ONLY OPERATING HOT/LOSING POWER NOISY UNDER LOAD BDU-10/21 Page 7
BDU-10/21 Troubleshooting Chart WARNING!!! THE VEHICLE SHOULD BE ON LEVEL GROUND AND THE ENGINE DISABLED BEFORE PERFORMING ANY ADJUSTMENTS SYMPTOM - OPERATES IN ONE DIRECTION ONLY POSSIBLE CAUSE CORRECTIVE ACTION -Inspect control linkage -Inspect drive belt & pulleys -Inspect check valves -Inspect easy ride valves -Repair or replace -Repair or replace -Repair or replace -Repair or replace SYMPTOM - NOISY POSSIBLE CAUSE CORRECTIVE ACTION -Check oil level & condition -Check for excessive loading -Chec
Minor Repair BDU-10/21 Minor Repair General Information Shaft Seals Minor repairs may be performed, following the procedures in this section, without voiding the unit warranty. Lip type seals are used on the pump input shaft, pump through shaft (not all models use the through shaft), motor output shaft and displacement control shaft. These seals can be replaced without major disassembly of the unit. However, replacement of the seals generally requires removal of the transmission from the machine.
BDU-10/21 Minor Repair Shaft Seals Charge Check Valves Inspect the sealing area on the shaft for rust, wear, or contamination. Polish the sealing area on the shaft if necessary. Remove the check valve plug with a 1/4" internal hex wrench. Wrap the spline or keyed end of the shaft with with a thin plastic or cellophane to prevent damage to the seal lip during installation. Lubricate the new seal with petroleum jelly and slide the seal over the shaft and press it into the housing bore.
Minor Repair Inspect the check balls (or poppets) and mating seats in the center section for damage or foreign material. Position the transmission so that the check valve port will be in the upright position (as shown) and install the check ball (or poppet), spring and plug (with o-ring) into the center section. Make sure the plug stem is properly positioned into the poppet or damage and failure will occur. Be certain the check ball does not fall into the closed loop passage.
BDU-10/21 Minor Repair Charge Pump The correct charge pump orientation is determined by the rotation of the pump shaft (CW or CCW). Before removing the charge pump, make note of, and/or mark its position to simplify the reassembly process. NOTE: Unlike the BDU-10L, some BDU-21L transmissions have an implement circuit designed into the charge pump cover. These covers are different and are not reversible. It is very important that they are reassembled in the same orientation as they were removed.
Minor Repair Disassembly Procedures Using a 5 or 6mm internal hex wrench, remove the two (2) screws holding the charge pump cover to the center section. BDU-10/21 For BDU-21L: Install the charge relief valve spring and ball. Install the drive pin. Install the gerotor assembly. Install a new o-ring and the charge pump cover. NOTE:The charge relief spring must enter the recessed hole in the charge pump cover. Torque the bolts evenly to 12-15 ft.lbs. (16.3-20.3 Nm). Remove the charge pump cover and o-ring.
BDU-10/21 Charge Pump Assembly Procedures For BDU-21L with implement circuit: Install the drive pin. Install a new o-ring on each side of the gerotor assembly and position the gerotor assembly onto the aligning pins in the same orientation as it was removed. Install the charge pump shim and the charge pump cover. Torque the bolts evenly to 18-25 ft.lbs.(24.4-33.9 Nm).
Major Repair BDU-10/21 Disassembly Procedures Prior to performing major repairs on the BDU remove the external components as described in the Minor Repairs section of this manual. These include the following: Bypass Valve Charge Check Valves Charge Pump Assembly For BDU-10S remove the filter element, filter washer and spring from the housing. Using a 6 mm internal hex wrench, remove the eight screws which retain the center section to the housing.
BDU-10/21 Disassembly Procedures Major Repair Remove the input shaft lip seal retaining ring. Pull the lip seal out of the housing bore. A hook type tool may be used to pry the seal out. Care must be taken to avoid damage to the housing bore, shaft sealing surface or bearing. Once removed, the seal is not reusable. Remove the bearing spacer washer. Remove the pump shaft assembly from the housing. Inspect the splines on the shaft for damage or unusual wear.
Major Repair Disassembly Procedures BDU-10/21 Reconditioning and Replacement of Parts After disassembly, all parts should be thoroughly cleaned in a suitable solvent. Inspect all parts for damage, nicks or unusual wear patterns. Replace all parts having unusual, excessive wear or discoloration. Inspect the sealing surfaces, bearing surfaces, and shaft splines. Polish the sealing areas on the shafts if necessary. Replace any worn or damaged parts.
BDU-10/21 Assembly Procedures Major Repair Install the swashplate into the housing. The slot on the swashplate must engage the slot guide block on the displacement control shaft. Use a tool such as a screwdriver or scribe to hold the guide block in position while installing the swashplate. BDU-10 Control Arm Installation BDU-10 Swashplate Components BDU-10 Pump Shaft Installation Install the pump shaft assembly into the housing. Install the bearing spacer washer.
Major Repair BDU-10/21 BDU-21 Swashplate Components BDU-21 with Swashplate Installed Install the thrust washer and pump cylinder block spring onto the pump shaft. Old Styles New Styles Install the springs piston washers and pistons into the cylinder block. The pistons must move freely in their bores. BDU-21 Swashplate Changes Hold the swashplate in position and measure the end play of the displacement control shaft using a dial indicator or a depth guage.
BDU-10/21 Major Repair Assembly Procedure Install the motor thrust bearing into the housing. NOTE: To simplify the installation of both the motor block and the pump block kits, wrap a rubber band snuggly around the pistons. This is intended to hold the pistons in their bores as the block kits are handled during installation. NOTE: It will be necessary to have a DRY journal bearing to prevent a hydraulic lock while installing the motor shaft. Install the motor shaft/cylinder block kit.
Major Repair BDU-10/21 For BDU-10 Check to see that the piston springs are centered in the cylinder block bores. If necessary, position them with a small screwdriver. Use caution to avoid damage to the cylinder block face. For BDU-10S Install the filter spring, washer and new filter element. Install the two aligning pins, and install a new gasket onto the housing. BDU-10 Center Section Assembly Install the eight bolts and torque evenly to 10-15 ft.lbs. (13.56-20.34 Nm).
BDU-10/21 Page 22 BDU-10S Parts Drawing & Parts List BDU-10/21
BDU-10S Parts Drawing & Parts List BDU-10/21 PARTS LIST NO. BDU-10/21 DESCRIPTION NO.
BDU-10/21 Page 24 BDU-10L Parts Drawing & Parts List BDU-10/21
BDU-10L Parts Drawing & Parts List BDU-10/21 PARTS LIST NO. BDU-10/21 DESCRIPTION NO.
BDU-10/21 Page 26 BDU-21L Parts Drawing & Parts List BDU-10/21
BDU-21L Parts Drawing & Parts List BDU-10/21 PARTS LIST NO. BDU-10/21 DESCRIPTION NO.
© 2009 HYDRO-GEAR Printed in U.S.A. Rev.
