This service manual provides information for servicing the chassis and mast components of various Cat lift truck models. It includes 12 sections covering general information, cooling, electrical, powertrain, transmission, front and rear axles, brakes, steering, hydraulics, masts/forks, service data, and a group index. The document lists specifications, components, removal/installation procedures, inspections, adjustments, and troubleshooting guides for the major vehicle systems. Serial number locations, vehicle dimensions, and technical specifications are provided for each truck model.

1. Chassis & Mast
Service Manual
99739-82100
For use with GM4.3L, G6 Engine Service Manual and
Fuel System Supplements
Lift
Trucks
®
GC35K AT87-00001-up
AT87A-00001-10230
AT87A-10231-20230
AT87A-20231-up
GC40K AT87-00001-up
AT87A-00001-10230
AT87A-10231-20230
AT87A-20231-up
GC40K STR AT87-00001-up
AT87A-00001-10230
AT87A-10231-20230
AT87A-20231-up
GC45K SWB AT87-00001-up
AT87A-00001-10230
AT87A-10231-20230
AT87A-20231-up
GC45K STR AT87A-20231-up
GC45K AT88-00001-up
AT88A-00001-10230
AT88A-10231-20230
GC55K AT88-00001-up
AT88A-00001-10230
AT88A-10231-20230
AT88A-20231-up
GC55K STR AT88-00001-up
AT88A-00001-10230
AT88A-10231-20230
AT88A-20231-up
GC60K AT89-00001-up
AT89A-00001-10230
AT89A-10231-20230
AT89A-20231-up
GC70K AT89-00001-up
AT89A-00001-10230
AT89A-10231-20230
AT89A-20231-up
GC70K STR AT89-00001-up
AT89A-00001-10230
AT89A-10231-20230
AT89A-20231-up

2. GROUP INDEX
1
2
3
4
5
6
7
8
9
10
11
12
Group Items
GENERALINFORMATION Vehicle Exterior, Models, Serial Number Locations, Dimensions, Technical Data.
COOLING SYSTEM Description, Removal and Installation, Inspection and Adjustment, Fan Belt
Inspection, Fan Belt Adjustment.
ELECTRICAL SYSTEM Description, Disassembly and Re-assembly, Major Electrical Components,
Battery Maintenance, Typical Open Circuit Voltage, Lamp Bulb Specifications,
Electrical System Schematics.
POWER TRAIN Specifications, Structure, Reduction Ratio, Procedures and Key Points for
Removal and Installation.
POWERSHIFTTRANSMISSION 1-Speed Transmission (GC35K-GC55K STR), Specifications, Structure,
Removal and Installation, Torque Converter, Transmission, Control Valve,
Adjustment, Automatic 2-speed Transmission (GC60K-GC70K STR),
Specifications, Structure, Transmission, Solenoid Valve, Adjustment,
Troubleshooting, Service Data.
FRONT AXLE Specifications, Structure, Procedures and Key Points for Removal and
Installation, Axle Shaft and Hub, Reduction Differential, Troubleshooting,
Service Data.
REAR AXLE Specifications, Structure, Procedures and Key Points for Removal and
Installation, Rear Axle Assembly, Steering Cylinder, Adjustment,
Troubleshooting, Service Data.
BRAKE SYSTEM Specifications, Structure, Master Cylinder, Wheel Cylinder, Wheel Brake,
Parking Brake Lever, Adjustment and Tests, Troubleshooting, Service Data.
STEERING SYSTEM Specifications, Structure, Procedures and Key Points for Removal and
Installation, Steering Control Valve, Troubleshooting, Service Data.
HYDRAULIC SYSTEM Specifications, Description, Removal and Installation, Disassembly and
Re-assembly, Inspection and Adjustment, Hydraulic Circuit Diagram,
Troubleshooting, Service Data.
MASTS AND FORKS Specifications, Description, Disassembly and Re-assembly, Inspection and
Adjustment,Troubleshooting, Service Data.
SERVICE DATA Inspection Standards, Periodic Replacement of Parts, Special Tool Table.

3. GENERAL INFORMATION
Vehicle Exterior .......................................................................................................................... 1 - 1
Models ........................................................................................................................................ 1 - 1
Serial Number Locations ............................................................................................................ 1 - 2
Dimensions.................................................................................................................................. 1 - 4
Technical Data ............................................................................................................................ 1 - 5
1

4. GENERAL INFORMATION
1
Vehicle Exterior
• This Service Manual deals with all components or systems of Cat lift trucks; except for the engine
and attachment, which are covered in the respective manuals.
Models
This manual applies to the following vehicle models (names).
102530A
Truck Models Transmission Serial Number Engine Mounted
GC35K
AT87-00001-up
GC40K AT87A-00001~10230
AT87A-10231-20230
GC40K STR AT87A-20231-up
GC45K SWB 1-Speed
GC45K STR
GM4.3L Gasoline Engine
GC45K AT88-00001-up
AT88A-00001~10230
GC55K AT88A-10231-20230
AT88A-20231-up
GC55K STR
GC60K
Automatic AT89-00001-up
GC70K 2-Speed AT89A-0000~10230
AT89A-10231-20230
GC70K STR AT89A-20231-up

5. GENERAL INFORMATION
1-2
Serial Number Locations
Name Plate
Chassis Serial Number
(Former Models) Gasoline Engine Serial Number
Mast Number Transmission Serial Number Chassis Serial Number
(New Models)

6. Chassis and Mast Model Identification
[Chassis]
GC 55 K
Generation designator
Maximum capacity
55 :5500kg (12000lb)
Maximum lifting height
(“33” stands for 3300mm.)
Order of the minor change
(“A” for the original, “B” for the first change, “C”
for the second change, and so on)
Applicable truck model designa-
tion 55:5.5 ton class
Kind of mast
A: simplex mast
B: duplex mast
C: triplex mast
Engine type
GC: gasoline engine type
[Mast]
A 55 A 33
GENERAL INFORMATION
1-3

7. Dimensions
F J K
G H
E
N
M
C
D
A
B
I
L
206999
GENERAL INFORMATION
1-4

8. GENERAL INFORMATION
1-5
Unit: mm (in.)
Truck Models
Ref.
GC35K GC40K
GC40K GC45K
No. STR SWB
Items
A Maximum lift Simplex mast 3050 (120) 2900 (114)
Simplex mast 150 (5.9) 160 (6.3)
Free lift 920 (36.2) 895 (35.2)
B (Floor to
Duplex mast
3.0 m (118 in.) mast 2.8m(112in.)mast
forktop) 800 (31.5) 920 (36.2)
Triplex mast
4.0 m (157 in.) mast 4.3m(169in.)mast
C Fork length 1220 (48)
D
Tilt angle 5/10 Simplex, Duplex mast
(forward – backward) deg. 6/5 Triplex mast
E Overall length (OLH) 2510 (98.5) 2550 (100) 2360 (93) 2620 (103)
F
Overall width Standard 1180 (46.5)
(outside) Wide tread (option) 1270 (50.0)
G
Overall height
2155 (85.0)
(to top of mast lowered)
H
Overall height
2155 (85.0)
(to top of overhead guard)
4250 (167) 4125 (162)
Simplex mast
I Overall height 4250 (167) 4080 (160.6)
(mast extended) Duplex mast 3.0 m (118 in.) mast 2.8m(112in.)mast
5250 (206.7) 5560 (218.9)
Triplex mast 4.0 m (157 in.) mast 4.3m(169in.)mast
J Tread (front)
Standard 940 (37.0)
Wide tread (option) 1040 (41.0)
K Tread (rear) 980 (38.5)
L Wheelbase 1575 (62.0)
M Rear overhang 485 (18.8) 525 (20.3) 335 (13.3) 565 (22.1)
N Underclearance (at frame) 150 (5.9)
Technical Data

9. GENERAL INFORMATION
1-6
GC45K STR GC45K GC55K GC55K GC60K GC70K GC70K
STR STR
2900 (114) 2350 (93)
160 (6.3) 165 (6.5)
895 (35.2)
2.8 m (112 in.) mast
895 (35.2) 900 (35.4)
4.0 m (157 in.) mast 3.5 m (138 in.) mast
1220 (48)
5/10 Simplex, Duplex mast 6/10 Simplex mast
6/5 Triplex mast 6/5 Triplex mast
2730 (107) 2910 (115) 2640 (104) 2950 (116) 2730 (107)
1320 (52.0) 1440 (56.5)
1420 (56.0)
2155 (85.0) 2205 (87.0)
2155 (85.0) 2205 (87.0)
4125 (162) 3585 (141)
4080 (160.6)
2.8 m (112 in.) mast
5560 (218.9) 4785 (188.3)
4.0 m (157 in.) mast 3.5 m (138 in.) mast
1015 (40.0) 1130 (44.5)
1120 (44)
965 (38.0) 1160 (45.5)
1780 (70.0) 1830 (72.0)
470 (18.1) 650 (26.1) 380 (15.1) 590 (23.1) 340 (13.1)
150 (5.9) 200 (7.9)
Unit: mm (in.)

10. GENERAL INFORMATION
1-7
GC40K GC45K
GC35K GC40K
STR SWB
Truck Models
Capacity/load center
kg/mm 3500/500 4000/500 4500/600
(lb/in.) (7000/24) (8000/24) (10000/24)
Maximum lift height Simplex mm (in.) 3050 (120) 2900 (114)
Lift speed (loaded) mm/sec. 540 (105) 390 (78.0)
Lowering speed (loaded) (fpm) 550 (108) 440 (86.5)
Mast tilt (forward-backward) degree 5/10
Free lift mm (in.) 150 (6.0) 160 (6.5)
Travel Powershift Loaded
km/h
19 (12.0) 18.5 (11.5)
speed transmission
No load (mph) 19.5 (12.5)
models
Minimum turning radius 2235 (88.0) 2285 (90) 2090 (82.5) 2340 (92.0)
Minimum
Standard
mm (in.)
2245 (88.5) 2295 (90.5) 2100 (82.5) 2350 (92.5)
intersecting isle
Gradeability at 1 mph Loaded 37 33 32 27
(1.6 km/h) No loaded
%
23.8 21.1 21.5 17.7
Gradeability at stall
Loaded 42 37 36 30
No loaded 23.8 21.1 21.5 17.7
Overall length to fork face 2510 (98.5) 2550 (100) 2360 (93) 2620 (103)
Overall Standard 1180 (46.5)
width Wide tread (optional) 1270 (50.0)
To top of mast
2200 (86.5) 2350 (92.5)
(lowered)
Overall To top of mast
4250 (167.5) 4130 (162.5)
height (extended)
To top of
2155 (85.0)
overhead guard mm (in.)
Wheelbase 1575 (62.0)
Standard 940 (37.0)
Tread
Front Wide tread
1040 (41.0)
(optional)
Rear 980 (38.5)
Overhang Rear 485 (18.8) 525 (20.3) 335 (13.3) 565 (22.1)
Underclearance (at frame) 150 (5.9)
Front
Single
22×9×16
Tire size wheels mm
Rear 18×7×12.12
Service weight
5200 (11500) 5600 (12300) 5700 (12700) 6500 (14300)
Single wheels -no load
(without load) Axle Front
kg (lb)
2050 (4600) 2025 (4400) 2150 (4900) 1925 (4200)
loading Rear 3150 (6900) 3575 (7900) 3550 (7800) 4575 (10100)
Technical Data
Weight
Work
performance
Traveling
performance
Dimensions

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12. GENERAL INFORMATION
1-8
GC45KSTR GC45K GC55K GC55K STR GC60K GC70K GC70K STR
4500/600 5500/600 6000/600 7000/600
(10000/24) (12000/24) (13500/24) (15500/24)
2900 (114) 2360 (93)
390 (78.0) 360 (71.0)
440 (86.5) 540 (106.0)
5/10 6/10
160 (6.5) 165 (6.5)
18.5 (11.5) 18 (11.5) 21 (13.0) 20.5 (12.5)
19.5 (12.5) 23 (14.5) 22.5 (14.0)
2440 (96.0) 2550 (100) 2350 (92.5) 2570 (101.0) 2400 (94.5)
2345 (92.5) 2455 (96.5) 2255 (89) 2395 (94.5) 2220 (87.5)
26 22.6 22.2 24.5 21.7 21.4
23.8 20.2 20.9 22.2 19.7 20.4
30 26 25 30 27 26
23.8 20.2 20.9 22.2 19.7 20.4
2730 (107) 2910 (115) 2460 (104) 2950 (116) 2700 (106)
1320 (52.0) 1440 (56.5)
1420 (56.0)
2350 (92.5) 2530 (99.5)
4130 (162.5) 2370 (93.0)
2155 (85.0) 2205 (87.0)
1780 (70.0) 1830 (72.0)
1015 (40.0) 1135 (44.5)
1115 (44.0)
965 (38.0) 1160 (45.5)
470 (18.1) 650 (26.1) 380 (15.1) 590 (23.1) 340 (13.1)
150 (5.9) 200 (7.9)
22×12×16 28×12×12
18×8×12.12 18×8×12.12 22×8×16
6600 (14500) 7200 (15800) 7400 (16200) 8800 (19300) 9500 (20900) 9700 (21300)
2625 (5700) 2425 (5300) 2625 (5700) 3300 (7300) 3300 (7200) 3500 (7500)
3975 (8800) 4775 (10500) 4775 (10500) 5500 (12000) 6200 (13700) 6200 (13800)

13. GENERAL INFORMATION
1-9
Truck Models
GC40K GC45K
GC35K GC40K
STR SWB
Items
Engine model GM4.3L
Type Gasoline
Cooling system Water cooled
No. of cylinders-arrangement 6-90°V
No. of strokes 4
Type of combustion chamber Semi-spherical
Valve arrangement Overhead
Type of cylinder liners Integral
Cylinder bore × stroke, mm (in.) 101.6×88.39 (4.00×3.48)
Displacement, cc (cu in.) 4293 (262)
Compression ratio 9.2 : 1
Rated output, PS/rpm 94/2450
Rated torque, kgf·m/rpm 31.0/1200
Min. rpm 750-800, 650-700
Max. rpm 2650-2700, 2600-2650
Dimensions (L×W×H), mm (in.) 710×620×740 (28.0×24.4×29.1)
Weight, kg (lb) 260 (573)
Installation position Rear
Ignition Spark
Firing order 1-6-5-4-3-2
Initial ignition timing, BTDC deg 0° Gasoline, 8° L.P.G., ECU Controlled
Fuel tank capacity, liter (U.S.gal) 66 (17.4)
Ignition coil Type Mold
Distributor
Type Pointless
Type of spark advance
Internal solid state circuit, ECU Controlled
control
Model AC #41-932, R42LTS
Spark plug Size, mm (in.) 14 (0.55)
Gap, mm (in.) 1.24 (0.0488), .89 (.035)
Carburetor Type Single Barrel, MPFI
Governor Type Electronic
Fuel pump Type Electromagnetic
Air cleaner Type × Number Cyclone with paper element × 1
Fuel
system
Engine
Ignition
system
MPFI specs in Bold. If not indicated in bold, specs are for Carbureted and MPFI systems.

14. GC45K STR GC45K GC55K GC55K STR GC60K GC70K GC70K STR
GM4.3L
Gasoline
Water cooled
6-90°V
4
Semi-spherical
Overhead
Integral
101.6×88.39 (4.00×3.48)
4293 (262)
9.2 : 1
92.6/2450
31.0/1200
750-800, 650-700
2650-2700, 2600-2650
710×620×740 (28.0×24.4×29.1)
260 (573)
Rear
Spark
1-6-5-4-3-2
0° Gasoline, 8° L.P.G., ECU Controlled
80 (21.1) 128 (34.0)
Mold
Pointless
Internal solid state circuit
AC #41-932, R42LTS
14 (0.55)
1.24 (0.0488), .89 (.035)
Single Barrel, MPFI
Electronic
Electromagnetic
Cyclone with paper element × 1
MPFI specs in Bold. If not indicated in bold, specs are for Carbureted and MPFI systems.
GENERAL INFORMATION
1-10

15. GENERAL INFORMATION
1-11
Truck Models
GC40K GC45K
GC35K GC40K
STR SWB
Items
Type Pressure feed
Oil pump Gear pump
Oil filter Paper element
Oil cooler Oil to water type
Refill capacities,
Oil pan 4.2 (1.1)
liter (U.S.gal)
Oil filter & cooler 0.8 (0.2)
Total 5.0 (1.3)
Type Forced circulation
Radiator Plate fins with pressure cap
Refill capacity, liter (U.S.gal) 18.2 (4.82)
Water pump Centrifugal type, V-belt driven, Serpentine belt driven
Thermostat/ Opening Temp F° Wax type/ 180
Type × number Group 24
Voltage, V 12
Capacity, AH (5Hr) 45
Type 3-Phase AC
Manufacturer MANDO, AC Delco
Rated output, V-A 12-50, 12-70
Regulator Built in IC type
Type Electromagnetic
Manufacturer Delco Remy
Voltage-output, V-kW 12 - 0.75
Starter
Engine
lubrication
system
Battery
Cooling
system
Alternator MPFI specs in Bold. If not indicated in bold, specs are for Carbureted and MPFI systems.

16. GC45K STR GC45K GC55K GC55K STR GC60K GC70K GC70K STR
Pressure feed
Gear pump
Paper element
Oil to water type
4.2 (1.1)
0.8 (0.2)
5.0 (1.3)
Forced circulation
Plate fins with pressure cap
11 (2.9)
Centrifugal type, V-belt driven, Serpentine belt driven
Wax type/ 180
Group 24
12
45
3-Phase AC
MANDO, AC Delco
12-50, 12-70
Built in IC type
Electromagnetic
Delco Remy
12 - 0.75
MPFI specs in Bold. If not indicated in bold, specs are for Carbureted and MPFI systems.
GENERAL INFORMATION
1-12