Caterpillar Cat 12G Motor Grader (Prefix 3WC) Service Repair Manual (3WC01067 and up)

1
Service Repair Manual

• Models
• Caterpillar Cat 12G Motor Grader

2
start by a) remove differential
1. Bend the lock away from nut (1) and loosen nut
(1) with tool (A).
3

1. Remove nut (1), lock (3) and washer (2).
2. Put the differential and the carrier in position
   as shown.

1. Remove wire (5) from the nuts on each side of the
   differential. Remove nuts (8).
2. Bend the locks away from bolts (6). Remove the
   bolts, the locks and locks (7) from the cap.
3. Remove cap (4) from the carrier.
4. Remove the dowel that holds the small cage in
   alignment with the cap.

8. Fasten a hoist and a strap to the differential
(9) as shown. Lift the differential and remove it
from the carrier. Weight is 240 lb. (109 kg).
4
9. Remove the ring and seal (10) from the carrier.

1. Remove small cage (11) from the differential.
   Remove the nut and the bearing cup from the
   cage.
2. Remove bearing (12) from housing (14) with
   tooling (B).
3. Remove bolts (13) and the washers that hold
   housing (14) to the clutch housing. Remove
   housing (14). Remove the brass washer from the
   inner face of housing (14).

13. Remove gear (15) from the spider gears.

1. Remove spider (18) and the gears and washers from
   the clutch housing.
2. Remove brass washers (16) and gears (17) from the
   spider.

5
16. Remove the brass bearings from the gears with
tooling (C).

1. Remove gear (19) from the housing.
2. Turn the bevel gear, clutch housing and the
   piston housing over.

1. Remove cage (20). Remove the nut, the bearing
   cup, the ring and the two seals from cage (20).
2. Remove bolts (21) and the washers that hold
   piston housing (22) to the bevel gear and the
   clutch housing. Remove piston housing (22).

1. Remove bearing (23) from the piston housing with
   tooling (B).
2. Turn the piston housing over.

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23. Remove brass washer (24) and piston (25) from
the piston housing. Remove the two seals from
the piston.

1. Remove discs (26) and disc assemblies (27) from
   the clutch housing.
2. Remove the pressure disc from the housing.

26. Remove pinion (28) from the carrier with
tooling (D).

1. Remove bearing cups (29) and (31) from the
   carrier with a punch and a hammer.
2. Remove seal (30) from the carrier.

8
29. Remove bearing (32) from the pinion with
tooling (E).
Assemble Differential (Unlocking)

1. Heat bearing (2) in oil to a temperature of 275
   F (135 C). Install bearing (2) on pinion (1).
2. Lower the temperature of the two bearing cups for
   the pinion. Install the bearing cups in
   differential carrier (3).

9
3. Install the seal in the differential carrier.
Install the seal with the lip toward the bevel
gear. Put a small amount of oil on the lip of
the seal.
4. Put pinion (1) in position on a block as
shown. Install tooling (A) on carrier (3) and
fasten a hoist to tooling (A). Lift the carrier
and put it in position over pinion (1) so bearing
(2) is in its seat in the bearing cup.

• Heat bearing (4) in oil to a temperature of 275
  F (135 C).
• Install bearing (4) on pinion (1). Make sure the
  bearing is in its seat in the bearing cup. Lift
  the carrier and remove the block from under the
  pinion. Put the carrier on the floor. Remove
  tooling
• (A) from the carrier.

1. Install the washer, the lock and nut (5) on the
   pinion. Do not tighten the nut.
2. Put two .250 in. (6.35 mm) dowels in the splines
   of the pinion. Put the dowels in position 180
   apart. Install tooling (B) over the pinion and
   the dowels.
3. Check the amount of torque needed to move the
   pinion without any preload on the pinion
   bearings. Remove the torque wrench from tooling
   (B).
4. Install a ratchet on tooling (B).

10
11. Install tool (C) on nut (5). Tighten nut (5)
with tool (C) while holding the pinion with the
ratchet. Tighten the nut enough to get a torque
of 6 4 lb. in. (6.9 4.6 cm.kg) more than the
torque needed to turn the pinion when the
bearings were not preloaded. Remove tooling (B)
and (C).

• Put clutch housing (7) in position on the floor
  as shown. Put a block of wood 2 1/2in. (63.5 mm)
  high in the center of the housing. Put gear (6)
  in position on the block.
• Put the pressure disc in position in clutch
  housing (7). Install the eight discs and the
  seven disc assemblies in the housing starting
  with a disc.
• NOTE Put clean SAE 30 oil on the discs and disc
  assemblies (8) at installation.
• Put the large brass washer on the face of gear
  (6). Make sure the hole in the washer is in
  alignment with the dowel in the housing.

1. Install the seals on the outside and the inside
   of the piston. Install the seals so the lips are
   toward the bottom of the bore for the piston in
   the piston housing. Put some clean SAE 30 oil on
   the lips of the seals. Install the piston in
   housing (10).
2. Heat bearing (9) in oil to a temperature of 275
   F (135 C). Install bearing (9) on the hub of
   piston housing (10).
3. Put piston housing (10) and the bevel gear in
   position on clutch housing (7). Make sure the
   holes in both housings and the bevel gear are in
   alignment.

11

1. Install three 5/8"-11 NC forged eyebolts (12) in
   piston housing (10). Install the bolts and the
   washers that hold the piston housing to the bevel
   gear and the clutch housing. Put a bar in
   position as shown in the eyebolts. Tighten bolts
   (11) to a torque of 185 10 lb. ft. (25.6 1.4
   mkg).
2. Remove the bar and the eyebolts.

• Turn the housings and the bevel gear over. Be
  careful that gear (6) does not fall out.
• Install the brass bearings in spider gears (14)
  with tool (E) and an arbor press.
• Install gears (14) and brass washers (16) on
  spider (15). Put the spider and the gears in
  position on the clutch housing as shown.
• NOTE Make sure the notches in the brass washers
  are up.
• Install gear (13) as shown on the spider gears.
  Install the large brass washer on the face of
  gear (13). Make sure the hole in the washer is
  in alignment with the dowel in the housing.

1. Put housing (18) in position on the clutch
   housing. Tool (F) can be used to make sure the
   notches in washers (16) are in alignment with the
   dowels in housing (18). Install bolts (19) the
   washers. Tighten the bolts to a torque of 60 5
   lb. ft. (8.3 0.7 mkg).
2. Heat bearing (17) in oil to a temperature of 275
   F (135 C). Install bearing (17) on the hub of
   housing (18).

12

1. Install the bearing cup and nut (22) in cage
   (20). Install ring (23) and the two seals on the
   cage.
2. Put the cage in position over the bearing.
3. Install the nut and the bearing cup in cage (21).
   Put cage (21) in position over the bearing.
4. Fasten a hoist and a strap to the differential.
   Put the differential in position on the carrier.
   Install the ring and seal between the carrier and
   cage (20). Make sure the opening in the cage is
   in alignment with the ring and seal.

30. Put cap (24) in position over the studs in
the carrier. Install the dowel in cage (21). Make
sure the dowel is in alignment with the hole in
cap (24).

• Install nuts (26) that hold the cap to the
  carrier. Tighten the four nuts to a torque of 75
  lb. ft. (10.4 mkg).
• Put the differential in position as shown. Put
  tooling (D) in position on the differential and
  against a tooth on the bevel gear. Turn the bevel
  gear to measure the gear clearance (backlash)
  between the pinion and the bevel gear.
• Make an adjustment to nut (22) under the bevel
  gear with tool (C), while keeping nut (25)
  finger tight against the top bearing, to get a
  gear clearance (backlash) of .008 .002 in.
  (0.20
• 0.05 mm).

13

1. Loosen nut (25). Tighten the nut by hand to
   remove the end play. Tighten nut (25) 1 to 1 1/2
   notches and measure the amount of change in
   dimension (X) with tooling (D). Dimension (X)
   must change by .005 .002 in. (0.13 0.05 mm).
2. Tighten nuts (26) to a torque of 280 20 lb. ft.
   (38.8 2.8 mkg). Turn the differential and
   measure the gear clearance (backlash) again.

• Put locks (27) in position on the cap. Install
  the locks and bolts that hold locks (27). Bend
  the locks against the bolts. Install wires (28)
  through the studs and nuts on each side of the
  differential.
• Install all the O-ring seals on the differential.
  end by
• a) install differential

14
Copyright 1993 - 2021 Caterpillar Inc. All
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Product MOTOR GRADER Model 12G MOTOR GRADER
3WC Configuration 12G Motor Grader 3WC01067-UP
(MACHINE) POWERED BY 3306 Engine
Disassembly and Assembly 12G, 130G 140G MOTOR
GRADER POWER TRAIN Media Number
-SENR7186-01 Publication Date -01/11/1989
Date Updated -24/02/2006
SENR71860015
Differential (Direct Drive) SMCS - 3258-15
3258-16
16
Disassemble Differential (Direct Drive)
17
start by a) remove differential
1. Remove all the O-ring seals from the
differential. Bend the lock away from nut (1) and
remove nut (1) with tool (A).
18

1. Remove lock (2) and washer (3) from the shaft.
2. Put the differential in position with the bevel
   gear up as shown.

1. Remove wire (7) from each side of the
   differential. Remove nuts (6) that hold the cap
   to the carrier.
2. Remove bolt (4) from each side of the
   differential.
3. Remove lock (5) from each side of the
   differential.

1. Remove cap (8) from the carrier.
2. Remove dowel (9) from each of the cages on the
   differential.
3. Fasten a hoist and a strap to the differential.

19
10. Remove differential (10). Weight is 160 lb.
(73 kg).
11. Remove cages (11) and (12). Remove the nuts
and the bearing cups from the cages.
13. Remove bearing cone (13) with tooling (B).
14. Turn the differential on its other end. Put
it on blocks as shown. Remove bolts (14) and the
washers that hold the hub and the bevel gear to
the other hub.
20

1. Install three 5/8"-11 NC forged eyebolts in hub
   (17) as shown. Fasten a hoist to eyebolts (15).
2. Remove hub (17) from the bevel gear. Remove the
   bevel gear from the other hub.
3. Remove bearing cone (16) from hub (17) with
   tooling (B).

18. Remove pinion (18) from the differential
carrier with tooling (C).

1. Remove bearing cups (20) and (21) from the
   differential carrier.
2. Remove seal (19) from the differential carrier.

21. Remove bearing cone (22) from pinion (18)
with tooling (D).
21
Assemble Differential (Direct Drive)

1. Heat bearing (2) in oil to a temperature of 275
   F (135 C). Install bearing (2) on pinion (1).
2. Lower the temperature of the two bearing cups for
   the pinion. Install the bearing cups in
   differential carrier (3).
3. Install the seal in the differential carrier.
   Install the seal with the lip toward the bevel
   gear. Put a small amount of oil on the lip of
   the seal.

4. Put pinion (1) in position on a block as
shown. Install tooling (A) on carrier (3) and
fasten a hoist to tooling (A). Lift the carrier
and put it in position over pinion (1) so bearing
(2) is in its seat in the bearing cup.
22

• Heat bearing (4) in oil to a temperature of 275
  F (135 C).
• Install bearing (4) on pinion (1). Make sure the
  bearing is in its seat in the bearing cup. Lift
  the carrier and remove the block from under the
  pinion. Put the carrier on the floor. Remove
  tooling
• (A) from the carrier.

1. Install the washer, the lock and nut (5) on the
   pinion. Do not tighten the nut.
2. Put two .250 in. (6.35 mm) dowels in the splines
   of the pinion. Put the dowels in position 180
   apart. Install tooling (B) over the pinion and
   the dowels.
3. Check the amount of torque needed to move the
   pinion without any preload on the pinion
   bearings. Remove the torque wrench from tooling
   (B).
4. Install a ratchet on tooling (B).

11. Install tool (C) on nut (5). Tighten nut (5)
with tool (C) while holding the pinion with the
ratchet. Tighten the nut enough to get a torque
of 6 4 lb. in. (6.9 4.6 cm.kg) more than the
torque needed to turn the pinion when the
bearings were not preloaded. Remove tooling (B)
and (C).
23

1. Heat bearing (6) in oil to a temperature of 275
   F (135 C).
2. Install bearing (6) on hub (7).

1. Heat bearing (9) in oil to a temperature of 275
   F (135 C). Install the bearing on hub (10).
2. Put hub (7) in position on blocks with its
   bearing down. Put bevel gear (12) in position on
   hub (7). Install three 5/8"-11 NC forged
   eyebolts in hub (10). Fasten a hoist to eyebolts
   (8). Put the hub in position on the bevel gear.
   Remove the hoist.
3. Install bolts (11) and the washers that hold the
   hub and the bevel gear to hub (7). Tighten the
   bolts to a torque of 185 10 lb. ft. (25.6 1.4
   mkg).
4. Remove the eyebolts from the differential.

• Install the bearing cups and nuts (13) in cages
  (14). Put the cages in position on the hubs.
• Fasten a hoist and a strap to the differential.
• Lift the differential and put it in position on
  the carrier. Remove the hoist and the strap.
• NOTE Make sure the holes in the cages are up.

24

1. Install dowels (16) in the cages.
2. Put cap (15) in position on the cages and the
   studs. Make sure the dowels in the cages are in
   alignment with the holes in the cap.

1. Install nuts (17) that hold the cap to the
   carrier. Tighten the nuts to a torque of 75 lb.
   ft. (10.4 mkg).
2. Put the differential in position as shown. Put
   tooling (D) in position on the differential and
   against a tooth on the bevel gear. Turn bevel
   gear (12) to measure the gear clearance
   (backlash) between the pinion and the bevel gear.

25

1. Make an adjustment to the nut under the bevel
   gear with tool (C), while keeping nut (18)
   finger tight against the top bearing, to get a
   gear clearance (backlash) of .008 .004 - .003
   in. (0.20 0.10 - 0.08 mm).
2. Loosen nut (18). Tighten the nut by hand to
   remove the end play. Tighten nut (18) 1 1/2 to 2
   notches and measure the amount of change in
   dimension (X) with tooling (D). Dimension (X)
   must change by .005 .002 in. (0.13 0.05 mm).
3. Tighten nuts (17) to a torque of 280 20 lb. ft.
   (38.8 2.8 mkg). Turn the differential and
   measure the gear clearance (backlash) again.

• Put locks (20) in position on the cap. Install
  the locks and bolts (19) that hold the locks.
  Bend the locks against the bolts.
• Install wires (21) on the studs on each side of
  the differential.
• Install all the O-ring seals on the differential.
  end by
• a) install differential

Copyright 1993 - 2021 Caterpillar Inc. All
Rights Reserved. Private Network For SIS
Licensees.
Thu Feb 11 232149 UTC0800 2021
26
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Previous Screen
Product MOTOR GRADER Model 12G MOTOR GRADER
3WC Configuration 12G Motor Grader 3WC01067-UP
(MACHINE) POWERED BY 3306 Engine
Disassembly and Assembly 12G, 130G 140G MOTOR
GRADER POWER TRAIN Media Number
-SENR7186-01 Publication Date -01/11/1989
Date Updated -24/02/2006
SENR71860016

• Transmission
• SMCS - 3150-11 3150-12 3150-15 3150-16
  3159-15 3159-16
• Remove Transmission
• start by
• remove fuel tank
• remove alternator
• remove fan drive
• remove transmission oil filter base
• remove transmission oil and scavenge pump
• remove parking brake rotochamber and release
  valve
• 1. Drain the oil from the transmission. Drain the
  coolant from the cooling system.

NOTE The plug that has a location in tube (4)
toward the front of the machine can be removed to
drain the coolant from tube (4). Put the plug in
position in tube (4) after draining the
coolant. 2. Remove hose clamps (1) from each end
of tube (4). Remove tube (4).
27

1. Put identification on oil lines (3) as to their
   location on the relief control valve. Disconnect
   oil lines (3) from the valve.
2. Loosen the nuts from bolts (2) on each side of
   the engine. Tighten bolts (2) until they are
   against the frame. Tighten the nuts.

5. Remove bolts (6) and retainer (9) that hold
couplings (8) to the transmission. Loosen nuts
(7) and slide couplings (8) free of the
transmission. Lift control cables (5) out of the
links on the transmission control valves.

1. Fasten a hoist to the lifting eyes on the
   transmission. Remove bolts (10) that hold the
   transmission to the flywheel housing. Remove nuts
   (11) that hold the transmission to the studs in
   the differential housing.
2. Move the transmission away from the engine and
   off the studs in the differential housing.

8. Lift transmission (12) and remove it from the
machine. Weight is 1500 lb. (680 kg).
Install Transmission
28

• Fasten a hoist to the lifting eyes on the
  transmission. Lower the transmission (1) into
  position in the machine.
• Move the transmission on to the studs in the
  differential housing and into the flywheel
  housing.
• NOTE To put the splines on the transmission
  adapter in alignment with the flywheel, turn the
  transmission oil pump shaft. To put the splines
  in the transmission in alignment with the splines
  on the differential input shaft, the following
  procedure can be used
• Drain the oil from the tandem housings.
• Remove the axles.
• Turn the differential input shaft with a prybar
  or a screwdriver while the transmission is being
  installed on the studs of the differential
  housing.
• Install the axles and fill the tandem housings
  with oil to their correct levels.

3. Install bolts (2) that hold the transmission
to the flywheel housing. Install the nuts that
hold the transmission to the differential
housing. Connect oil lines (3) to their correct
locations on the relief control valve. Remove
the hoist.
4. Put three control cables (7) in position on
the valve links. Put couplings (6) in position in
the transmission housing. Tighten nuts (4)
against the couplings. Put retainer (5) in
position over the couplings. Install the bolts
that hold the retainer to the transmission
housing.
29

• Put tube (8) in position on the machine. Tighten
  hose clamps (9) at each end of tube (8) over the
  tube. Loosen the nuts on bolts (10) on each side
  of the machine. Move bolts (10) away from the
  frame. Tighten the nuts.
• Fill the transmission with oil to its correct
  level. Fill the cooling system with coolant to
  its correct level.
• end by
• install parking brake rotochamber and release
  valve
• install transmission oil and scavenge pump
• install transmission oil filter base
• install fan drive
• install alternator
• install fuel tank

Disassemble Transmission
start by
30
a) remove transmission
1. Install the transmission on tooling (C).
Remove bolts (1) and the lockwashers that hold
the cover to the transmission. Remove cover (2).
2. Remove links (3) from the transmission
hydraulic control valves.
3. Remove bolts (8) and plates (7). Move the four
sleeves (5) free of the transmission hydraulic
control valves. NOTE Do not remove bolts (4)
and (6) at this time. Bolts (4) and (6) hold the
control valves to the transmission.
4. Install a 3/8"-16 NC forged eyebolt in the
transmission case. Install tooling (B) in the
eyebolt.
31
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1. Install tooling (A) on the transmission case and
   on the control valves. Connect tooling (B) to
   tooling (A) as shown. Remove bolts (4) and (6).
   Remove transmission hydraulic control valves (9)
   with tooling (B). Weight is 90 lb. (41 kg). See
   DISASSEMBLE HYDRAULIC CONTROL VALVES for
   disassembly of the control valves.
2. Remove the four sleeves from the transmission.
   Fasten tooling (D) to the lifting eyes on top of
   the transmission. Remove the bolts that hold the
   transmission to tooling (C). Remove the bolts and
   cover (10).

1. Install two 1/2"-13 NC forged eyebolts and two
   nuts in the transmission on top of the output
   flange. Fasten tooling (D) to the two eyebolts.
2. Turn the transmission on its end with tooling
   (D). Put the transmission in position on tooling
   (E). Remove tooling (D) and the eyebolts.

1. Remove O-rings (11) and O-ring (12) from the
   housing.
2. Remove bolt (13) and bolt (14) that hold the
   planetary transmission in the transmission case.

1. Install two 5/8"-11 NC forged eyebolts (15) in
   the housing. Fasten a hoist to the eyebolts.
2. Remove the planetary transmission from the
   transmission case. Weight is 560 lb. (254 kg).
3. Put the transmission on three blocks.

33
Make sure the input gear for the planetary
transmission is on top of the blocks. If the
input gear is not on top of the blocks, other
components can fall out the bottom of the
transmission when a retaining ring is removed.
14. Remove bolts (16). Remove O-ring seal (18).
Lift housing (17) enough to remove springs (19)
and plungers (20). Remove the housing. Weight is
85 lb. (39 kg). Remove the O-ring seal that is
under the flange on housing (17).
15. Remove bolts (22). Bend the locks (23) away
from bolts (21). Remove bolts (21) and locks
(23).
16. Remove hub (25). Remove four discs (24) and
three plates (26). These discs and plates are for
the parking brake clutch.
34

1. Install tooling (F) as shown against plate (29).
   Put springs (28) in compression with tooling (F)
   and a press.
2. Remove retaining ring (27). Slowly release the
   compression on springs (28). Remove tooling (F).
   Remove the plate and the springs.

1. Remove cage (30) from the hub. Remove O-ring seal
   (31) and the internal ring that is under the
   O-ring seal.
2. Remove external ring (32) from the hub.

1. Remove piston (34).
2. Remove ring gear (33).

35
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