ZT-4400 Service and Repair Manual BLN-0081 January 2018
TABLE OF CONTENTS Foreword........................................................1 Return to Neutral Assembly Option....17 Description and Operation.............................2 Control Arm Assembly.......................18 Introduction....................................................2 Filter and Filter Cover.........................19 Brake Assembly..................................20 General Description 2-6 Bypass Actuator.................................21 Hydraulic Schematic...............
FOREWORD Headquartered in Sullivan, Illinois, Hydro-Gear is a world leader in the design, manufacture, and service of quality hydrostatic transaxles for the lawn and garden industry. The mission of our company is to be recognized by our customers and the industry as a world-class supplier and the quality leader in everything we do. This Service and Repair Manual is designed to provide information useful in servicing and troubleshooting the Hydro-Gear® ZT-4400.
DESCRIPTION AND OPERATION INTRODUCTION The purpose of this manual is to provide information useful in servicing the Hydro-Gear® ZT-4400® Hydrostatic Transaxle. This manual includes the ZT-4400’s general description, hydraulic schematic, technical specifications, servicing and troubleshooting procedures. Should servicing be required, the exterior of the transaxle will need to be thoroughly cleaned before beginning most procedures. Do not wash the transaxle immediatly after use.
DESCRIPTION AND OPERATION (CONTINUED) HYDRAULIC SCHEMATIC Figure 1 is a schematic of the hydraulic oil circuit. The oil supply for the hydraulic system of the ZT-4400 is also utilized for lubricating the components of the final drive assembly. The input shaft and pump cylinder block are turned in one direction only by the engine/drive belt/pulley combination. Output of the oil flow is controlled by the direction and amount that the variable swashplate is angled.
EXTERNAL FEATURES ZT-4400 Expansion Tank Port / Fill Port Input Shaft Brake Arm Filter Cover — Inboard View— Expansion Tank Port / Fill Port Oil Fill Vent Port (not necessary to remove) Fan Pulley Return to Neutral Hub — Side View— 4 ZT-4400
EXTERNAL FEATURES ZT-4400 Control Arm Control Arm Control Arm with Return to Neutral Return to Neutral ZT-4400 5
TECHNICAL SPECIFICATIONS ZT-4400 TECHNICAL SPECIFICATIONS Displacement Pump 0.73 in3/rev [12cc/rev] Motor 1.0 in3/rev [16.4cc/rev] Input Speed Maximum (no load) 3600 rpm Minimum (loaded) 1800 rpm Weight on Tires (per unit) 720 lbs Axle Diameter 1 3/8 inches [35 mm] Parking Brake Type Internal Disk Brake 55 lbs [25 kg] Weight of Unit PRODUCT IDENTIFICATION The model and configuration of the ZT-4400 can be determined from the label shown below. HYDRO-GEAR SULLIVAN, IL. U.S.A.
SAFETY This symbol points out important safety instructions which, if not followed, could endanger the personal safety and/or property of yourself and others. Read and follow all instructions in this manual before attempting maintenance on your transaxle. When you see this symbol - HEED ITS WARNING. Wear appropriate clothing. Loose or hanging clothing or jewelry can be hazardous. Use the appropriate safety equipment, such as eye and hearing protection, and safety-toe and slip-proof shoes.
TROUBLESHOOTING WARNING Do not attempt any servicing or adjustments with the engine running. Use extreme caution while inspecting the drive belt assembly and all vehicle linkage! Follow all safety procedures outlined in the vehicle owner’s manual. In many cases, problems with the ZT-4400 are not related to a defective transaxle, but are caused by slipping drive belts, partially engaged bypass valves, and loose or damaged control linkages.
SERVICE AND MAINTENANCE NOTE: Any servicing dealer attempting a warranty repair must have prior approval before conducting maintenance of a Hydro-Gear® product unless the servicing dealer is a current Authorized Hydro-Gear Service Center. EXTERNAL MAINTENANCE Regular external maintenance of the ZT-4400 should include the following: 1. Check the vehicle operator’s manual for the recommended load ratings. Insure the current application does not exceed load rating. 2.
FLUID CHANGE PROCEDURE This transaxle is designed with a serviceable filter. To ensure constant fluid quality levels and longer life, an initial oil and filter change at 100 hours is recommended. Subsequent changes are recommended at 400 hour intervals minimum, or yearly, whichever comes first. Oil Fill Level The following procedure can be performed with the transaxle installed in the vehicle, and the vehicle on level ground. Apply the bypass valve and lock the vehicle parking brake. 1.
PURGING PROCEDURE Due to the effects air has on efficiency in hydrostatic drive applications, it is critical that it be purged from the system. These purge procedures should be implemented any time a hydrostatic system has been opened to facilitate maintenance or any additional oil has been added to the system. Air creates inefficiency because its compression and expansion rate is higher than that of the oil approved for use in hydrostatic drive systems.
RETURN TO NEUTRAL SETTING WARNING POTENTIAL FOR SERIOUS INJURY Certain procedures require the vehicle engine to be operated and the vehicle to be raised off the ground. To prevent possible injury to the servicing technician and/or bystanders, insure the vehicle is properly secured. The return to neutral mechanism on the transaxle is designed to set the directional control into a neutral position when the operator removes their hand from the control lever.
TEAR DOWN AND REASSEMBLY HOW TO USE THIS MANUAL Each subassembly illustrated in this section is illustrated by an exploded view showing the parts involved. The item reference numbers in each illustration are for assembly instructions only. See page 39 for part names and descriptions. A complete exploded view and item list of the transaxle is provided on pages 38 and 39. Many of the parts and subassemblies of this transaxle can be removed and serviced independently of other components.
TRANSAXLE REMOVAL NOTE: It is necessary to remove the ZT-4400 from the vehicle before performing the repair procedures presented in this section. Before starting any disassembly, make certain that your work area is neat and clean. Clean the external parts of the transaxle. The following procedures are presented in the order recommended for a complete tear down of the transaxle. Do not disassemble the unit any farther than necessary to accomplish the required repairs.
TOOLS Miscellaneous R EQUIRED TOOL S 3/8” Drive Ratchet Rubber Mallet Large External Retaining Ring Pliers AN-08 (1/4 Allen) T-25 Torx T-40 Torx 3 Jaw Puller TORQUES 1/2” socket 3/4” socket 9/16” socket 1 1/8” socket 1 7/16” socket 3/8” socket Sockets As a general rule, use the low end of the torque spec on fasteners when reassembling the unit. Item REQUIRED TORQUE VALUES Description Torque Operation 17 HFHCS 280-340 in-lbs [31.6-38.
FAN AND PULLEY AXLE HUB ASSEMBLY 1. Remove the locknut (139). 1. Remove the axle cap and discard (122). 2. Remove the fan (138). 2. Remove the cotter pin and discard (121). 3. Remove the pulley (136). 3. Remove the castle nut (120) and washer (123). Refer to Figure 8 Refer to Figure 8 4. Remove the pulley hub (137). 4. Remove the taper hub assembly (118) and discard. Assembly 1. Reassemble all parts in the reverse order of disassembly. 2.
RETURN TO NEUTRAL ASSEMBLY OPTION Refer to Figure 9 Disassembly 1. Remove all items previously discussed in their recommended order. 2. Remove the spring (164). 3. Remove the Torx head screw (161) and discard. Remove the washer (163). 4. Remove the scissor arm (162). Remove the Allen head screw (156) and the RTN control arm (154). 5. Remove the washer (160), neutral arm (159) and the spacer (158). Inspection 1. Inspect all parts for excessive wear or damage. Replace if necessary. Assembly 1.
CONTROL ARM ASSEMBLY Refer to Figure 10 Disassembly Inspection 1. Remove all items previously discussed in their recommended order. 1. Inspect all parts for excessive wear or damage. Replace if necessary. 2. Remove the lock nut (172) and washer (160). Discard both items. Assembly 3. Remove the Torx head screw (156) and discard. 4. Remove the control arm (154) and spacer (170). 5. Remove the stud (171) only if damaged. 1. Reassemble all parts in the reverse order of disassembly. 2.
FILTER AND FILTER COVER Refer to Figure 11 Disassembly Assembly 1. Remove the filter cover (102). 1. Install the new filter (100). 2. Remove the O-ring (101) from the cover (102) and discard. 2. Install the new O-ring (101) onto the cover (102). 3. Remove the filter (100) and discard. 3. Install the filter cover (102). Refer to torque chart on page 15. Inspection 1. Inspect all parts for wear or damage. Replace as necessary. 2. Check for old filter grommet stuck on the filter tube.
BRAKE ASSEMBLY Refer to Figure 12 Disassembly Inspection 1. Remove all items previously discussed in their recommended order. 1. Inspect all parts for wear or damage. Replace as necessary. 2. Mark the orientation of the brake arm (191) before removal. Assembly 3. Remove the retaining ring (92) and discard. 1. Reassemble all parts in the reverse order of disassembly. 4. Remove the brake handle (91), spring (96), and bushing (90). 2. Install new seal (88) from seal kit. 5.
BYPASS ACTUATOR Refer to Figure 14 Disassembly Inspection 1. Remove all external items previously discussed in their recommended order. 1. Inspect the actuator bypass rod (126) for wear or damage. Replace if necessary. 2. Remove the retaining ring (127) and discard. NOTE: Take care to insure that the actuator bypass rod is free of burrs that may cut the lip seal. 3. Remove the bypass rod (126) and the clip retaining ring (128) as a single item.
SIDE HOUSING Refer to Figure 15 Disassembly Assembly 1. Remove all external items previously discussed in their recommended order. 1. Reassemble all parts in the reverse order of disassembly. 2. Remove the screws (17), then separate side housing from main housing. 2. Install new seals (115 and 150). 3. Remove the axle shaft seal (115) and trunnion seal (150). Discard both seals. Inspection 1. Inspect the bearing and bushing areas in the side cover for excessive wear or damage.
AXLE SHAFT AND PLANETARY GEAR SET Refer to Figure 16 Disassembly Inspection 1. Remove all external items previously discussed in their recommended order. 1. Inspect all items of the planetary gear set for wear and or damage. 2. Remove the axle bearing (110) and washer (113). Assembly 3. Remove the axle shaft (112) and bull gear (73) assembly. 1. Reassemble all parts in the reverse order of disassembly. 4. Remove the retaining ring (111). Remove bull gear (73) from axle shaft (112). 5.
REDUCTION GEARS Refer to Figure 17 Disassembly Inspection 1. Remove all external items previously discussed in their recommended order. 1. Inspect items for wear and or damage. Replace if necessary. 2. Remove washer (74) and reduction gear set (71) as an assembly and set aside. Remove second washer (74) and jack shaft pin (70). Assembly 1. Reassemble all parts in the reverse order of disassembly.
REMOVE FILTER TUBE Refer to Figure 18 Disassembly Inspection 1. Remove all external items previously discussed in their recommended order. 1. Inspect items for wear and or damage. Replace if necessary. 2. Remove screw (36) and oil tube retainer (104). Assembly 3. Remove the oil tube (103). 1. Reassemble all parts in the reverse order of disassembly. 4. Remove the grommet (105).
INPUT SHAFT Refer to Figure 18 Disassembly 1. Remove all external items previously discussed in their recommended order. 66 2. Remove the retaining ring (66) and discard. 55 3. Remove the lip seal (55) and discard. 64 4. Remove the washer (64). 5. Remove the pump shaft (61) with pressed on bearing. NOTE: Remove the bearing from pump shaft only if worn or damaged. 63 62 5. Remove the wire ring retainer (63) and discard. Remove the bearing (62) from the pump shaft (61a). 61 Inspection 1.
SWASHPLATE Refer to Figures 19, 20 Disassembly Assembly 1. Remove all external items previously discussed in their recommended order. 1. Reassemble all parts in the reverse order of disassembly. 2. Remove the swashplate (40), thrust bearing (45), and pump block (49). 2. Apply a light coating of oil to all running surfaces. Inspection 3. Reassemble the items of the pump block assembly. Place the thrust bearing assembly (85) so the thick race contacts the pump block pistons. 1.
CENTER SECTION Refer to Figure 21, and 22 Disassembly Assembly 1. Remove all external items previously discussed in their recommended order. 1. Reassemble all parts in the reverse order of disassembly. 2. Remove the center section bolts (18) and (19). 2. When tightening the fasteners, refer to the table on page 15 for the required torque values. See figure 22 for order of bolt installation. Inspection 1. Inspect for surface wear damage.
MOTOR SHAFT ASSEMBLY Refer to Figures 23, 24 Disassembly Inspection 1. Remove all external items previously discussed in their recommended order. 1. Inspect for scratches and or damage to the brake rotor (82). 2. Remove retaining ring (30), the spring (31), motor block (23), and the bypass plate (125). 2. Inspect the bypass plate (125) for excessive wear. 3. Remove the retaining ring (34), gear (33), brake rotor (82), washer (74) and motor shaft (22). 30 31 3.
BRAKE ASSEMBLY Refer to Figure 25 Disassembly Inspection NOTE: If the brake is working properly and the brake components are not damaged, do not remove the brake assembly. 1. Inspect the puck (81) for excessive wear. 1. Remove the brake shaft nut (87) and washer (86). 1. Reassemble all parts in the reverse order of disassembly. 2. Remove the brake shaft (85), the splined cam (84), the puck cam (83) and brake puck (81). NOTE: The brake components are only available in the center section kit.
THRUST BEARING Refer to Figure 26 Disassembly Assembly 1. Remove all external items previously discussed in their recommended order. 1. Reassemble all parts in the reverse order of disassembly. 2. Remove the thrust bearing. 2. Place the thrust bearing assembly (27) so the thick race contacts the motor block pistons. Inspection 1. Inspect the races of the thrust bearing (27) for wear or damage.
INSPECTING THE HYDRAULIC COMPONENTS Refer to Figure 27-29 Inspect the running surfaces on the pump block, motor block, and both running faces on the center section. Note: The pump face on the center section has machined groves as seen in Figure 28. These are not defects. These “sealing” surfaces should be smooth in appearance without scratches, scoring, nicks or abrasions.
SHOCK VALVES, CHARGE RELIEF, CHARGE PUMP, MAGNET Refer to Figure 30 Disassembly Inspection 1. Remove all items previously discussed, in their recommended order. 1. Inspect the all items for wear or damage. Replace if necessary. 2. Pry off the charge galley cap (15). 2. Clean off the magnet (35). Only disassemble if damaged. NOTE: Mark orientation of the shock valves before removing. 3. Remove the shock valve assembly (10) and disassemble.
ASSEMBLY AFTER A COMPLETE TEARDOWN If the unit has been torn down completely, the following summary identifies the assembly procedures necessary to completely assemble the unit. Each assembly procedure is located by a page reference. A small consistent bead (approximately. 1/16 – 1/8 inch) of the sealant around the housing face will be sufficient. Use sparingly.
SEALANT APPLICATION Figure 31, Sealant Application Diagram ZT-4400 35
SIDE HOUSING – SCREW TIGHTENING SEQUENCE Starting with the number “1” screw location, tighten sequentially through to “14.” Torque each screw to 230 – 290 lb-in (25.9 – 32.7 Nm). NOTE: As a general rule, use the low end of the torque specification.
CASTLE NUT (113) ALTERNATE TORQUE METHOD NOTE: The ideal method for installing a new hub and nut is utilizing a torque wrench capable of 275 ft-lbs. If a 275 ft-lbs torque wrench is not available please use the alternative procedure outlined in this document. All parts need to be clean and free of lubrication. Tools: Procedure: 1. 1. 2. 3. 4. 5. 2. 3. 4. 5. 6.
ZT-4400 EXPLODED VIEW 38 ZT-4400
ZT-4400 TRANSAXLE PARTS LIST 1 2 10 11 17 18 19 20 22 23 27 30 31 33 34 35 36 40 45 49 54 57 61 64 66 70 71 73 74 82 90 91 92 ZT-4400 Housing, Main Housing, Side Kit, Shock Valve Kit, Shock Valve Screw, Housing Screw, Hex Flange 3/8-16 X 1.5 Screw, Hex Flange 3/8-16 X 3.
GLOSSARY OF TERMS Axial Piston: Type of design for hydraulic motors and pumps in which the pistons are arranged parallel with the spindle (input or output shaft). Bypass Valve: A valve whose primary function is to open a path for the fluid to bypass the motor or pump. Also referred to occasionally as the freewheel valve or dump valve. Case Drain Line (Return Line): A line returning fluid from the component housing to the reservoir.
Hydrostatic Transmission: The combination of a hydraulic pump and motor in one housing to form a device for the control and transfer of power. Inlet Line: A supply line to the pump. Integrated Zero-Turn Transaxle: The combination of a hydrostatic transmission and gear case in one housing to form a complete transaxle. Manifold: A conductor which provides multiple connection ports.
NOTES 42 ZT-4400
NOTES ZT-4400 43
© 2015 HYDRO-GEAR Printed in U.S.A.
