The document provides information on servicing the CQ20-30 transaxle: - It describes the construction of the TA18 transaxle assembly and its components. - Maintenance procedures are outlined, including checking fluid level and changing fluid and filter every 1,000 hours. - Pressure specifications and check points for the regulator valve, converter, clutches, and other components are provided. - The process for adjusting the service brakes via the backing plate or wheel hub opening is described in detail. Cleanliness and proper adjustment are emphasized to prevent issues.

1. CQ 20/25/30 D/L
SERVICE MANUAL
RATED CAPACITY: 2000 – 3000kg
Book No. SM 794
Aug. 2008

2. Truck Models Covered by this Manual
This manual consists of “base” module that pertains
to all CQ20-30 models and other modules that per-
tain only to specific models. Manuals shipped with
the truck contain the base module and the modules
specific to the purchased truck.
You may, however, purchase specific modules and
expand your manual to fully cover multiple models.
To do so, order the desired modules as you would
any other Clark part.
Arrangement and Use of this Manual
Clark arranges parts and service procedures by stan-
dardized Groups. In this manual, Groups are similar
to “chapters”.
Each Group begins with a table of contents that shows the
Sections contained within the Group. Lengthy Sections
also begin with a table of contents.
Each Group and Section has an identifying name and
number, or “ID”.
Each page also has a unique ID. The page ID con-
sists of three numbers separated by hyphens. The
three numbers represent the Group number, the Sec-
tion number, and the page number. For example,
“00-1-2” on the lower corner of the page indicates
Group 00, Section 1, page 2.
The Group number sometimes has a letter or letters
added to it in parentheses if one or more variations of
the Group exist. For example, if the truck has a stan-
dard transaxle, Group 06 is expressed as “06(S)”; if
the truck has a hydrostatic transmission, Group 06 is
expressed as “06(H)”.
You can quickly locate a specific point in the manual
by using the headers and footers that appear on every
Section page. The following illustration points out
these areas.
This manual is intended for the use of trained service
personnel. Please read Group SA, “Safe Mainte-
nance”, and the Operator’s Manual before working
on or operating the truck.
Manual ID Group-Section-Page
Group ID

3. CONTENTS
SM 794 CONTENTS
CONTENTS
(Group Index)
Group PS. Periodic Service
Group 00. Engines
Group 01. Cooling System
Group 02. Fuel System
Group 03. Air Induction System
Group 06. Transaxle
Group 12. Ignition System
Group 13. Electrical System
Group 22. Wheels and Tires
Group 23. Brake / Inching System
Group 25. Steering Column and Gear
Group 26. Steer Axle
Group 29. Hydraulic Pump, Sump, and Filters
Group 30. Hydraulic Control Valve/Lift Circuit
Group 32. Tilt Cylinders
Group 34. Upright
Group 38. Counterweight, Sheet Metal & Chassis
23
30
29
13
00
03
02
22
38
06
25
32
34
26
01
13

4. GROUP PS
SM 794 PS-0
GROUP PS
PERIODIC SERVICE
Maintenance Schedules ............................ Section 1
The Planned Maintenance Program ....... Section 2

5. Group PS, Periodic Service
SM 794 PS-1-1
“Periodic Service” and “Planned
Maintenance”
The term “periodic service” includes all maintenance
tasks that should be performed on a regularly scheduled
basis.
The term “Planned Maintenance” indicates a formalized
program of basic inspections, adjustments, and lubrica-
tions that the Clark service organization provides custom-
ers at a prescribed interval, usually 50-250 hours. The
recommended basic “Planned Maintenance” procedure is
given in Section 2 of this Group.
The current Section,“Maintenance Schedules,” specifies
all maintenance tasks—including Planned Maintenance
tasks—that should be performed periodically, and sug-
gests intervals at which they should be performed.
Determining Maintenance Intervals
Time intervals on the charts on the next four pages and
elsewhere in this manual relate to truck operating hours as
recorded on the hourmeter, and are based on experience
Clark has found to be convenient and suitable under nor-
mal operation. Standard operating condition classifica-
tions are:
Normal Operation: Eight-hour material handling, mostly
in buildings or in clean, open air on clean, paved surfaces.
Severe Operation: Prolonged operating hours or constant
usage.
Extreme Operation:
• In sandy or dusty locations, such as cement plants,
lumber mills, and coal dust or stone crushing sites.
• High-temperature locations, such as steel mills and
foundries.
• Sudden temperature changes, such as constant trips
from buildings into the open air, or in refrigeration
plants.
If the lift truck is used in severe or extreme operating con-
ditions, the maintenance intervals should be shortened
accordingly.
IMPORTANT
MAINTENANCE INTERVALS. If the lift
truck is used in severe or extreme operating
conditions, the maintenance intervals should
be shortened accordingly.
Since the operating environments of lift
trucks vary widely, the above descriptions
are highly generalized and should be applied
as actual conditions dictate.
Section 1
Maintenance Schedules

6. Group PS, Periodic Service
SM 794 PS-1-2
LUBRICATION
Perform periodic maintenance, replacement and lubricating according to following lubrication chart to maintain
optimum condition. Otherwise service, life will be reduced and breakdowns may occur frequently.
LUBRICATION CHART
Lubricant
Replace
Check
Grease
Engine oil
Transaxle oil
Antifreeze
Hydraulic oil
Fuel
Brake fluid
CO
HO
G
EO
EO
BO
BO
TO TO
EO
CO
CO
G
G
FO
HO HO
G
G
EO
TO
FO
BO
Every 10 hours or daily
Every 200 hours or monthly
Every 500 hours or every 3 months
Every 1000 hours or every 6 months
Every 2000 hours or yearly
Transaxle oil filter
Mast mounting
RH, LH(2points)
Lift chain
RH, LH(2points)
Brake fluid
Transaxle oil
Engine oil
Engine oil filter
Coolant
Steer king pin
RH, LH(4points)
Steering linkage
RH, LH(4points)
Fuel (LPG)
Tilt cylinder end
RH, LH(2points)
Hydraulic oil
Hydraulic oil filter
Hydraulic breather
Wheel bearing
RH, LH(2points)
Air cleaner

7. GROUP 06
SM 794 06-0
Structure and Maintenance......................Section 1
Disassembly................................................Section 2
Assembly......................................................Section 3
GROUP 06
TRANSAXLE

8. Group 06, TRANSAXLE
SM 794 06-1-1
Construction
TA18 Transaxle assembly includes:
• Torque converter
• Single–speed forward and reverse powershift
transmission with integral differential and drive
axle
• Full–floating straight drive axle
• Automotive–type drum and shoe brakes
• Gear–driven pump drive
• Electric shift control, hydraulic inching control
Power flow is from torque converter turbine, to tur-
bine (clutch) shaft and gears, then through either for-
ward gear or reverse idler shaft, to the output gear
mounted on final drive pinion shaft.
Transmission and differential are housed in a one–
piece transmission case.
Torque converter housing joined to transmission
case through an adaptor (or spacer) plate holds the
converter stator support and reverse idler outer bear-
ing.
Pump drive is from converter impeller hub gear,
through an idler gear to the pump gear mounted on
charging pump shaft.
Final drive pinion gear shaft, mounted in tapered
roller bearings at both ends in transmission case, is
adjusted for mounting distance, and ring and pinion
gear contact by, shim a pack installed behind the pin-
ion gear inner tapered roller bearing cup in the trans-
misson case. Pinion shaft bearing preload is
adjusted with shims behind outer bearing cone on
the pinion shaft.
Section 1
Structure and Maintenance

9. Group 06, TRANSAXLE
SM 794 06-1-2
Final drive ring gear is bolted to differential carrier.
Differential support is by opposed tapered roller
bearings mounted on inner end of wheel end hous-
ings, which are bolted to openings in transmission
case at the sides of the differential. Differential bear-
ing preload and ring gear clearance (backlash) is
maintained by shims placed behind differential bear-
ing cones on wheel end housings. Adjustment of dif-
ferential bearing preload or ring gear backlash
requires trial assembly, checking, and disassembly
of wheel end housings until correct adjustment is
obtained.
Drive axle wheel hubs/brake drums are supported by
double tapered roller bearings on outer end of wheel
end housings. Drive axle shaft flange bolted to wheel
hubs are full–floating in differential. Service brake
backing plates are bolted to mounting flanges on
wheel end housings.
Wheel bearings are lubricated from the transaxle
sump.
Control valve is mounted on pad at top of transmis-
sion case. Oil from charging pump flows via filter and
pressure regulator to control valve through an exter-
nal oil supply line. Oil from control valve is delivered
to clutches through passages in housing and oil dis-
tributor sleeve and seal rings at forward–clutch end
of turbine/clutch shaft. Excess pump oil volume and
converter–out oil, flows to oil cooler and returns to
transmission housing at base of control valve, then
through center of turbine/clutch shaft back to con-
verter.
Hydraulic Circuit

10. Group 06, TRANSAXLE
SM 794 06-1-3
Service Maintenance
Service
The transaxle has two service openings:
1. Dipstick / oil fill tube in central side axle housing.
2. Drain plug, in bottom of transmission case.
Fluid Level Check
Check the transaxle fluid level with:
• Fork lift on a level surface
• Engine idling with transmission in NEUTRAL
• Oil at operating temperature 82~93°C
(180~200°F)
① Remove the transaxle oil level plug the front of
central housing of driving wheel.
② The oil level is correct when the oil reaches the
full mark on dipstick.
③ Add recommended fluid only, as required.
Fluid and Filter Change
It is recommended to:
• Drain and replace the transaxle fluid every 1000
operating hours.
• The oil should be drained when warmed to oper-
ating temperature, 82~93°C (180~200°F)
• Replace the transaxle oil filter every 1000 oper-
ating hours. See NOTICE below.
IMPORTANT
When the transaxle is new or rebuilt, it is rec-
ommended to change the oil filter after the
first 50 hours and again after 1000 operating
hours.
① Remove drain plug from bottom of transmission
case. Drain old oil into suitable drain pan.
② Remove old oil filter. The oil filter is mounted
near the top of converter housing above trans-
mission.
Take special care when removing the filter to
avoid oil remaining in filter from draining onto
floor. Loosen the filter using a filter wrench.
Remove filter while holding a pad of cloth or
other absorbent material under the open end to
absorb any excess oil that may drain out of filter.
③ Install a new oil filter. Follow the installation
instructions printed on filter.
Always use genuine CLARK parts
!
!
!

11. Group 06, TRANSAXLE
SM 794 06-1-4
Refilling the Transaxle
After drive axle and transmission housing has
drained completely,
• Install drain plug.
• Loosen the oil level plug and fill the oil upto the
plug hole.
• Start the engine and run at idle speed (700~800
rpm) in NEUTRAL for 2~3 minutes to prime the
converter and cooler lines.
• Recheck oil level with engine running at idle
speed. [82~93°C (180~200°F)]
• Check for leaks at drain plug and oil filter.
Specification
Pressure Specification
• Regulator valve pressure : 1108~1451kPa
(160~210 psi) @ 1800 rpm
Check Point : Oil supply line at converter
• Converter In/Lube Pressure : 176~314kPa
(26~45 psi ) @ 1800 rpm
Check Point : Return from cooler
• Converter Safety Valve Pressure (Trans in NEU-
TRAL) : 729~827kPa (105~120 psi) @ 1800 rpm
(Refefence only) with line to cooler blocked.
Check Point : None
• Clutch Pressure (Forward, Reverse applied) :
1034kPa (150 psi) @ 700~800 rpm idle
Normally 103kpa (15 psi) less than regulator
pressure 1000kpa (145 psi min)
Check Point : At control valve (1/8 NPTF)
• Clutch Pressure (in NEUTRAL) : Regulator pres-
sure

12. Group 06, TRANSAXLE
SM 794 06-1-5
NOTICE
!
• All rpm’s noted are engine speed.
• All clutch pressures are at engine idle speed
with clutch engaged, unless otherwise noted.
• Oil at operating temperature 82~93C(180~200F)
• Refer to following illustrations for check
point locations.
Pressure Check Points

13. Group 06, TRANSAXLE
SM 794 06-1-6
Service Brake Adjustment
Preparation
1. The service brakes on the transaxle may be
adjusted from the inner side through the backing
plate (all models), or from the outer side through
access openings in the wheel hub/brake drum
(later models).
2. Brake clearance is measured between brake
shoe and drum, with brakes fully released.
Brake clearance : 0.255~0.304 mm (.010~.012
in)
CAUTION
!
Be sure transmission directional control is
in NEUTRAL and fork lift prevented from
moving when parking brake is released.
3. Release parking brake.
IMPORTANT
!
Do not overtighten brakes.
It is very difficult to release the ratchet
wheel pawl and back off adjustment of the
brake.
Adjustment at Backing Plate
1. Remove the 4 dust plugs in brake backing plate.
2. Use a feeler (thickness) gauge to check the
clearance between each shoe and drum. Use a
brake adjuster tool to rotate the adjuster ratchet
wheel in the brake.
3. Use a screwdriver to push on and release the
ratchet pawl when it is necessary to back off
adjustment (increase clearance) of the brake.
4. Carefully adjust clearance between brake shoes
and drum to 0.255~0.304 mm (.010~.012 in)
measured at dust plug openings at outer sides
of backing plate.
5. Replace the dust plugs in brake backing plate
when adjustment is completed.

14. Group 06, TRANSAXLE
SM 794 06-1-7
Adjustment at Wheel Hub
Openings in the wheel hub/brake drum have been
provided for easier access to check and adjust the
service brakes from the outer side. Requires
removal of drive wheel and tire assembly.
Some models may have only a slot for measuring
brake clearance ; adjustment is made through the
plug openings on backing plate. Later models have a
slot and circular opening for access also to the
adjuster. The opening is enclosed with a dust cover
held in place by a single screw.
1. Remove wheel and tire assembly from wheel
hub.
WARNING
!
Pneumatic Tire Wheels
Before loosening wheel mounting bolts or
nuts, release the air pressure from the tire.
Failure to release the air pressure from the
tire can result in serious injury or death.
2. Remove dust cover from access opening in
wheel hub/brake drum.
3. Use feeler (thickness) gauge to check the clear-
ance between each shoe and drum. Use a
brake adjuster tool to rotate the adjuster ratchet
wheel in the brake.
4. Use a tool with a hook to pull on and release the
ratchet pawl when it is necessary to back off
adjustment (increase clearance) of the brake.
IMPORTANT
!
Do not overtighten brakes.
It is very difficult to release the ratchet
wheel pawl and back off adjustment of the
bake.
5. Carefully adjust clearance between brake shoes
and drum to 0.255~0.304 mm (.010~.012 in)
measured at slot opening. Move slot by rotating
brake drum to check clearance at the illustrated
position for each brake shoe. (20–01–6)
6. After adjusting brakes, install dust cover over
access opening in the wheel hub.
7. Install wheel and tire assembly on the drive axle
wheel hub.
8. Install wheel mounting lug nuts and tighten to
spec : 637~718 Nm (471~531 lbf·ft)

15. Group 06, TRANSAXLE
SM 794 06-2-1
Precaution
• Before attempting any repairs or overhaul of
this assembly, please read through the entire
disassembly and assembly procedures first.
Cleanliness is of extreme importance in the
repair and overhaul of this assembly.
• The exterior surface of the unit MUST be thor-
oughly cleaned of all dirt and foreign substances
to prevent contamination of the parts during dis-
assembly and overhaul. Perform all disassembly
and assembly work in a clean area. Protect all
components from dust and dirt while repairs are
being made.
• Keep all parts in order as disassembly
progresses. Take care to properly identify each
part and its order of removal. If necessary, keep
notes and put marking on parts using a nonde-
structive marker such as a felt–tipped pen.
Remove Auxiliary Subassemblies
1. Remove torque converter assembly by carefully
sliding it off the turbine (clutch) shaft and stator
support.
2. Disassemble converter drive plate and adaptor,
as needed. Remove the :
3. Oil filter
4. Charging pump
5. Oil supply line assembly
6. Transmission control valve assembly
!
Section 2
Disassembly

16. Group 06, TRANSAXLE
SM 794 06-2-2
Wheel End
1. Loosen and remove the axle shaft fasteners.
2. Remove axle shaft.
3. Unbend (straighten) the lockplate tabs from the
bolt heads of the wheel bearing retainer plate
fasteners.
4. Remove the bearing retainer plate fasteners.
5. Remove the lockplate, bearing retainer plate
and wheel bearing shims.
6. Pull wheel hub out to loosen bearing (you may
have to tap on hub or pry at brake backing
plate), remove outer wheel bearing, then
remove the wheel hub/brake drum assembly
with inner wheel bearing and oil seal.
8
7
4
6 5 3
2 1

17. Group 06, TRANSAXLE
SM 794 06-2-3
IMPORTANT
!
This oil seal is a type that seals internally, and is
lined with sealing compound on the inner diame-
ter that sticks and seals to the spindle.
Removing the wheel hub from the spindle breaks
that seal. Replace with new seal each time that
the wheel hub is removed from wheel end hous-
ing.
7. Before removal of wheel end housing, mark the
housing and the transmission case for same–
location matching at reassembly. Loosen and
remove the housing bolts and washers.
8. Remove wheel end housing from transmission
case.
9. If the differential bearing on the inner end of the
wheel end housing is to be removed and
replaced, use a bearing puller, if necessary.
Wire bearing shims to wheel end housing for
storage until reassembly.
10. Repeat procedures of Steps 1 through 9 for
opposite wheel end disassembly.
11. Remove the differential assembly from trans-
mission case.

18. Group 06, TRANSAXLE
SM 794 06-2-4
Brake Assembly Removal
Brake removal is optional for brake overhaul as nec-
essary.
1. Remove the upper brake shoe return springs.
2. Remove lower return spring.
3. Remove brake shoe hold–down (guide) springs.
4. Disconnect parking brake cable.
Remove the brake shoes.
5. Remove brake backing plate fasteners and
washers.
6. Remove backing plate and parking brake cable
assembly from wheel end housing.
7. Remove drive axle support and spacer from
wheel end housing.

19. Group 06, TRANSAXLE
SM 794 06-2-5
Separation of Converter Housing and Adaptor Plate
1. Remove the fasteners and washers which
mount the converter housing to transmission
case through the adaptor plate.
2. From other side, remove the bolts and washers
which mount adaptor (spacer) plate to converter
housing.
3. Remove the clutch pressure–regulating valve
assembly (also oil filter mounting base).
IMPORTANT
!
Pry only at the dowel pins to remove adap-
tor plate. Dowel pins must be removed
before reassembly. See later instructions.
4. Separate converter housing from adaptor plate.
5. Remove impeller hub gear from stator support.
6. Remove pump drive idler gear and bearing,
outer and inner thrust washers, and idler shaft.
7. Remove adaptor plate from transmission case.
Stator Support Removal From
Adaptor Plate
1. The stator support is held in place by two retain-
ing rings, one on each side of the adaptor plate.
2. To remove stator support :
− Remove front (converter end) retaining ring from
ring groove and move ring and impeller gear
thrust washer toward stator support seal surface.
− Push stator support to the rear (towards trans-
mission side) far enough to expose rear retainer
ring.
− Remove rear retaining ring.
− From the front, pull stator support from adaptor
plate.

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21. Group 06, TRANSAXLE
SM 794 06-2-6
Clutch Assembly, Idler Gear & Pin-
ion Shaft Removal
1. Move the reverse idler gear and clutch assem-
bly apart far enough to allow the idler shaft to be
pulled out of the inner bearing.
2. Remove the clutch assembly and reverse idler
shaft together.
3. Remove the turbine (clutch) shaft rear bearing.
4. Remove the clutch shaft oil distributor retaining
set screw (internal hex) from valve mounting
base.
5. Remove the oil distributor. Note the recess in
distributor for retaining set screw.
6. Loosen and remove the pinion shaft nut.
Hold or block the pinion shaft with a brass bar or
similar soft material to prevent turning.
7. Remove the pinion shaft outer bearing and
shims. Keep the shims with the bearing and pin-
ion shaft.
8. Remove output gear retaining ring from pinion
shaft (inside transmission case).
9. Remove output gear (move pinion shaft away).
10. Remove pinion shaft and inner bearing through
differential housing.
11. If pinion bearings are to be replaced, drive the
cups from the housing inside transmisson case.
12. Remove inner pinion bearing cup and shims
from differential side.
Wire shims to transmission housing for stor-
age until reassembly.
13. As required, remove oil suction (pickup) tube
assembly from transmission case.
!

22. Group 06, TRANSAXLE
SM 794 06-2-7
Clutch Disassembly
(Forward & Reverse Clutch Procedure Are The Same) • Reverse Clutch Disassembly Illustrated
1. Remove outer clutch hub gear thrust bearing
and thrust washers, clutch hub gear, and inner
clutch hub thrust bearing and thrust washers.
2. Disassemble the two clutch gear bearings and
spacer from internal bore of clutch gear hub.
3. Remove clutch disc end plate retainer ring and
clutch disc end plate.
4. Remove inner and outer clutch discs.
5. Remove clutch return spring retainer ring.
6. Remove clutch return (release) springs
(Belleville washers). Note assembly arrange-
ment.
7. Remove clutch piston wear plate.
8. Remove clutch piston by turning clutch upside
down and tapping the shaft on a block of wood.
9. Remove and discard clutch piston sealing rings.
10. Repeat procedures, steps 1 through 9, for for-
ward clutch disassembly.

23. Group 06, TRANSAXLE
SM 794 06-2-8
Differential Disassembly
1. Use a small drift pin or rod to remove the differ-
ential pinion pin, lock pin.
2. Remove the pinion pin.
3. Rotate the pinion gears and washers to remove
them from the differential housing.