4.236 & T4.236 DIESEL ENGINES Section J: Balancer Unit Caterpillar

Section J: Balancer Unit
1.1. Balancer Unit, Front Mounted
2.2. To Remove
3.2. To Dismantle
4.2. Important
5.2. Use of "Loctite"
6.2. To Re-assemble the Unit
7.2. To Replace
8.1. Balancer Unit, Centre Mounted
9.2. To Remove
10.2. To Dismantle
11.2. To Fit new Bushes and Bearings
12.2. Frame Bushes
13.2. Frame end cover bushes
14.2. Needle Bearings
15.2. Use of Loctite
16.2. To Assemble
17.2. To Fit Balance Weights
18.2. To Fit Idler Gear
19.2. To Refit and time Balancer to Engine

On certain applications a balancer unit is incorporated in the engine sump, from which the lubricating oil pump is driven. The balancer unit can be either a front or centre mounted type.

It is important to note that, on some of these applications, a crankshaft is fitted which has no balance weights, as distinct from the crankshaft on other applications which can incorporate balance weights which are forged in the manufacturing process.

When replacing a crankshaft, the correct type should be fitted as determined by the displaced crankshaft.

It is also important to note that balancer units vary according to which side of the engine, the lubricating oil filter is fitted. When replacing a balancer unit, always ensure that the correct type is being fitted.

Balancer Unit, Front Mounted

To Remove

Remove the lubricating oil sump.

Remove the balancer unit assembly, complete with the lubricating oil pump.

To Dismantle

Remove the seven setscrews and washers securing the lubricating oil pump to the balance unit.

Remove the oil pump, complete with backplate and driving gear, if possible. Should the backplate and driving gear remain in position on the balance unit they must be removed separately.

From the front of the balancer unit, remove the idler gear hub retaining nut or setscrew.

Remove the idler gear hub, idler gear and thrust plate.

Remove the two socket headed grubscrews in each of the balance weights.

Press out each of the shafts in turn, towards the drive end, taking care that the keys in the shafts do not foul the bushes in the drive end of the balancer frame. Insufficient care could result in the bushes being damaged and this would mean replacement of the complete frame assembly.

Both balance weights may now be lifted from the balancer frame, complete with their respective gears

Should it be necessary to renew either the balance weights or coupling gears, remove the three socket headed capscrews in each balance weight assembly and take off the coupling gears.

Remove the two thimbles which locate between the frame and the cylinder block.

Remove the seven plugs from the oilways in the balance frame and clean out the oilways.


When refitting the socket headed capscrews which secure the coupling gears to the balance weights, also the socket headed grubscrews in the balance weights and the idler gear and hub securing stud, "Loctite" grade 241, should be used on the threads in the following manner:-

Use of "Loctite"

Thoroughly clean both male and female threads with a suitable degreasing fluid (not kerosene), allowing 15 minutes for it to dry. It is recommended that, where possible, "Locquic" Q Activator be used for this purpose as it will considerably reduce the curing time.

Apply a light coating of "Loctite" grade A, to both male and female threads, fit the stud or screw and tighten to the specified torque.

A curing period of 24 hours (1 hour if "Locquic" Q Activator has been used) at room temperature must now be allowed before the engine is started.

To Re-assemble the Unit

NOTE: Replacement bushes for the balancer frame are not serviced separately and if wear is evident, a replacement balancer frame assembly must be obtained, complete with bushes already line-bored. Later balancer units have needle race bearings fitted in place of bushes and are not interchangeable with bushes.

When needle race bearings are fitted, then the balancer unit drive and driven shafts, bearings, keys and oil pump gears must be changed after 5,000 hours operation.

Balancer units incorporating needle race bearings were introduced as from the following Engines Nos

212U5821L212UA188070L236U159054L236UA102116 (rear end rope seal)236UA103692L (rear end lip seal)248U34896L248UA123725 (rear end rope seal)248UA124785L (rear end lip seal)

Current balancer units have reversed balance weights where the gears are fitted to the rear of the weights instead of the front as shown in Fig. J.1. and thicker section roller race bearings are fitted.

When replacing needle or roller race bearings, they should not be hammered in, but pressed in using a suitable dolly. Needle race bearings should be pressed in to a minimum of 0.008 in (0,20 mm) from the end of the housing. Thicker section roller race bearings should be pressed in so that a clearance of 0.030/0.040 in (0,76/1,02 mm) is left between the end faces of all bearings and inside face of the frame bosses.


1. Idler Gear Hub Retaining Nut or setscrews (later engines) ... 1

2. Idler Gear Hub ... 1

3. Idler Gear Hub Dowel ... 1

4. Idler Gear Assembly (complete with bush) ... 1

5. Idler Gear Thrust Plate ... 1

6. Driving Shaft ... 1

7. Driven Shaft ... 1

8. Balance Weight Gear Retaining Screws ... 6

9. Balance Weight Gear ... 2

10. Balance Weight ... 2

11. Balance Weight Locating Screw ... 4

12. Idler Gear Hub Stud ... 1

13. Balance Weight Frame Plug ... 5

14. Frame to Cylinder Block Thimble ... 2

15. Frame Assembly (complete with bushes) ... 1

16. Balance Weight Frame Plug ... 2

17. Balance Weight Locating Key ... 2

Current engines have reversed balance weights where the gears are fitted to the rear of the weights.

NOTE: Replacement bushes are not serviced separately for the idler gear. A replacement idler gear, complete with pre-finished bush must be fitted.

The stud which secures the idler gear and hub to the balancer frame is available as a spare part but need not be removed from the balancer frame unless it requires replacing.

Having renewed any part showing signs of wear, proceed as follows:-

Replace the seven plugs in the oil drillings of the balancer frame.

Should it have proved necessary to renew the idler gear and hub securing stud, fit the new stud, using "Loctite".

Should it have been necessary to remove the coupling gears from the balance weights, using "Loctite", reassemble, finally tightening the socket headed capscrews to a torque of 11 lbf ft (1,52 kgf m) -15Nm.

Where necessary, renew the shaft keys.

Stand the balancer unit on its lubricating oil pump end face.

Place the two balance weights complete with gears into the frame, coupling the gears so that when the shafts are partially entered, the keys are in the same relative position, i.e. both at top dead centre or both at bottom dead centre.

Ensure that each shaft is related dead centre to the bushes at the front and rear of the frame and press in until the drive shaft (with integral gear) is fully home and the end of the driven shaft is flush with the drive end face of the balancer frame.

Extreme care must be taken when pressing in the shafts, to prevent the keys from touching the drive end bushes (where fitted) or the needle bearings as they pass through. The slightest damage caused this way could result in seizure of the unit and severe consequential damage to the engine.

Using "Loctite", fit the two grubscrews to each balance weight and tighten to a torque of 71/2 lbf ft (1,03 kgf m) -10 Nm. Do not omit degreasing before using "Loctite".

Fit thrust plate, idler gear and hub so that the single centre punch mark on the idler gear registers between the two punch marks on the integral balance shaft gear. Ensure that the dowel in the hub locates in the corresponding hole in the balancer frame.

Fit the idler gear and hub retaining nut or setscrew and tighten to a torque of 40 lbf ft (5,53 kgf m) - 54 Nm.

Revolve the unit by means of the idler gear to ensure that the action is quite free.

Place the oil pump back plate in position at the rear of the balancer unit.

Fit the oil pump drive gear onto the end of the balancer drive shaft.

Fit the oil pump idler gear onto the idler shaft in the pump and refit the pump housing to the balancer unit, securing with seven setscrews and washers to a torque of 21 lbf ft (2,90 kgf m) -28 Nm.

Revolve the balancer unit idler gear once more to ensure freedom.

Continue revolving the idler gear until the punch marks once more coincide. This may take several revolutions.

To Replace

Place the two locating thimbles into their bores and refit the balancer unit to the cylinder block, ensuring that the single centre punch mark on the crankshaft gear registers between the two punch marks on the idler gear of the balancer unit.

The balancer unit is now timed to the engine. When fitting the balancer unit to an engine where the front end has not been stripped, it will not be possible to observe the punch mark on the crankshaft gear for the purpose of timing the unit to the engine.

In this case, the engine should firstly be rotated so that either the piston of No. 1 or No. 2 cylinder is at top or bottom dead centre. Bottom dead centre is preferable as any error greater than one gear tooth will cause a foul between the weights and the connecting rod in this position, making it obvious that the balancer unit has been wrongly timed.

Revolve the idler gear until the single centre punch mark on the idler gear registers between the two punch marks on the balancer shaft drive gear.

Suitably mark with chalk, a tooth of the drive gear to align with another chalk mark on the frame.

In this position, fit the balancer unit to the engine, checking that the weights have not moved by observing alignment of the chalk marks.

As a further check, observe that the single punch mark on the idler gear still registers between the two punch marks on the balancer shaft gear, in alignment with the gear centres. Accuracy in timing the balancer unit to the engine is essential as an error will cause serious consequential damage to the engine.

The ability to turn the engine over by hand is not necessarily proof that the balancer unit is correctly timed.

Secure the balancer unit to the cylinder block with the four setscrews and washers, tightened to a torque of 40 lbf ft (5,6 kgf m) - 54 Nm.

After fitting the balancer unit to the cylinder block and especially in the case where a new balancer unit frame has been incorporated, check to see that there is clearance between the balancer unit frame and No. 1 main bearing cap.

Refit the sump in the normal manner, as described in the relevant service literture.

Balancer Unit, Centre Mounted

To Remove

Drain the lubricating oil.

Remove sump.

Support the balancer unit (Caution, the unit weight approximately 55 lbs (25 kg) and remove the six bolts and washers.

To Dismantle

1. Remove idler gear assembly (see 16, 17, 19 and 21 Fig. J.2) by removal of the idler gear hub (see 16, Fig. J2). Use a 0.984 in (25 mm) AF Allen key in the idler gear hub Allen key socket or remove setscrew. Ensure that the idler gear assembly is removed complete to prevent parts from damage.

2. Remove balance weights cover.

3. Remove driveshaft/gear (see 15, Fig. J.1) and balance weight drive gear (see 3, Fig. J.2) by removal of locknut (see 4, Fig. J.2). Lightly use hammer and drift on shaft at locknut end position to release Loctite seal of shaft and balance weight drive gear spline Ensure shaft threads are not damaged and that the needle bearings are not damaged when the driveshaft is slid out.


1. Drive shaft end float, 0.0067/0.0137 in (0,17/0,35 mm).

2. Drive shaft rear bearing, dim. below machined surface 0.0079/0.118 in.

3. Balance weight drive gear.

4. Balance weight drive gear nut.

5. Balance unit frame.

6. End cover.

7. Lub. oil transfer plate.

8. Lub. oil suction pipe.

9. Drive shaft gear bearing.

10. Joint.

11. Lub. oil pump assembly.

12. Drive shaft, rear of bearing to front face 5.126/5.164 in. (130,2/131,2 mm).

13. Drive shaft front bearing.

14. Drive shaft front bearing, dim. below front face of frame 0.098/0.118 in (2,5/3,0 mm).

15. Drive shaft gear.

16. Balancer unit idler gear.

17. Idler gear hub.

18. Idler hub, Allen key recess or setscrew.

19. Idler gear hub bearing.

20. Idler gear end float, 0.003/0.009 in (0,08/0,23 mm).

21. Idler gear thrust washer.

4. Remove lubricating oil pump and suction pipe (see 8 and 11, Fig. J.2) by removal of three setscrews which hold the lubricating oil pump to the balancer frame.

5. Remove lubricating oil pump relief valve as follows:

a) Spring pin which holds relief valve assembly in position.

b) Spring cap, spring and plunger.

NOTE: The spring pin must be removed carefully to ensure that the spring and spring cap are not lost or cause damage to the operator when the spring pressure is released.

On assembly ensure the correct relief valve is used. Turbocharged engines have a higher rated spring than the naturally aspirated engine for higher lubricating oil pressure.

J3 Oil Transfer Cover Plate
Raised symbols to indicate:

A. Square socket head plug position.

B. Hexagonal socket head plug position.

C. Oil flow indication for RH or LH lub. oil filter position.

6. Remove balancer lubricating oil transfer plate (see 7, Fig. J.2). Note position of lubricating oil direction indicators on the outside of the transfer plate for correct assembly purposes (see Fig. J.3).

7. Remove frame end cover (see 6, Fig. J.2).

8. Remove balance weights carefully so driven weight gear does not damage the bearings.

J4 Right Hand mounted oil filter
RH mounted lub. oil filter.

A. Short hexagonal socket head plug position.

B. Long square socket head plug position.

J5 Left Hand mounted oil filter
LH mounted lub. oil filter.

A. Short hexagonal socket head plug position.

B. Long square socket head plug position.

9. Do not remove lubricating oil direction plugs (see 'A' and 'B', Fig. J.4 and J.5). Removal of the plugs can damage the threads and make the frame faulty, a new frame will then be needed. When right or left hand lubricating oil filters are fitted to the engine the correct balancer unit with the correct lubricating oil flow must be fitted to suit the filter position.

10. Clean all lubricating oil passages with a Kerosene spray. Dry lubricating oil passages with air pressure.

11. Check front and rear driveshaft/gear needle bearings for damage or wear, renew if necessary.

12. Check balance weight bearings for damage or wear, replace if necessary.

13. Check balance weights for wear or damage on shafts and gears (see 'A' and 'D', Fig. J.7), renew if necessary.

To Fit new Bushes and Bearings


A. Mandrel for brush bearings.

B. Mandrel for driveshaft Front needle bearings.

C. Mandrel for driveshaft Rear needle bearings.

NOTE: Where needle bearing and brush bearing are renewed, they must be pressed into position with mandrels made to the dimensions given in Fig. J.6.

Frame Bushes

Clean and lubricate parent bores and press in bushes (see 'A' and 'D-, Fig. J.7) in a continuous movement until they are 0.098/0.108 in (2,50/2,75 mm) below the machined face (see 'B', Fig. J.7) with mandrel.

Frame end cover bushes

Clean and lubricate parent bores (see 6, Fig. J.2) and press in bushes (see 'D', Fig. J.7) in a continuous movement until the are 0.108/0.128 in (2,75/3,25 mm) below the machined face (see 'C', Fig. J.7) with mandrel.

Needle Bearings

Clean and lubricate parent bores and with mandrel press in rear needle bearing (see 9, Fig. J.2) in a continuous movement until the bearing is 5.124/5.164 in (130/131 mm) from the front of the frame (see 12, Fig. J.2).

Press in front needle bearing (see 13, Fig. J.2) with mandrel in a continuous movement until the needle bearing is 0.098/9.118 in (2,5/3,0 mm) below the front face of the frame (see 14, Fig. J.2).

Use of Loctite

Where the use of 'Loctite' is recommended, the correct grade must be used. Thoroughly clean threads or surfaces with a suitable fluid (not Kerosene) to remove any grease or similar deposits and give time to dry before 'Loctite' compound is applied to the threads. The Loctite must be given 24 hours at room temperature to harden before the unit is used.

To Assemble

1. Ensure hollow location dowel is in position and fit lubricating oil pump (see 11, Fig. J.2) and tighten setscrews to 22 lbf ft (3,3 kgf m) 30,0 Nm.

2. Fit engine lubricating oil relief valve assembly. Ensure the relief valve bore is clean, not damaged or worn. Lubricate bore and position plunger, the protrusion on the plunger must face out. Position spring over plunger protrusion, fit spring cap. Compress spring and fit the spring pin in its loction holes to keep the lubricating oil valve assembly in position.

3. Lubricate needle bearings (see 9 and 13, Fig. J.2) and fit driveshaft/gear (see 15, Fig. J.2) carefully so the needle bearings are not damaged with the shaft splines. Ensure the shaft splines that drive the lubricating oil pump are aligned with the lubricating oil pump splines when the driveshaft/gear is slid into position.

4. Add a small amount of 'Loctite' grade 274 to the outer end of the balance weights drive gear splines (see 3, Fig. J.2) and locknut (see 4, Fig. J.2) threads. Fit gear (see 3, Fig. J.2) and locknut (see 4, Fig. J.2) and tighten locknut to 70 lbf ft (9,7 kgf m) 95 Nm. To fit locknut it will be necessary to slide driveshaft from gear to give enough clearance. Ensure in this operation Loctite does not enter the bearing as this can cause needle roller failure. To tighten the locknut it is necessary to hold the locknut with an open end spanner (3/4 in AF) and use a suitable peg tool which inserts into the two holes in the shaft gear for use with a torque spanner.

5. Ensure driveshaft/gear and engine lubricating oil pump turn freely. Check driveshaft end float. 0.0067/0.0137 in (0,17/0,35 mm).


A. Bush frame.

B. Bush, dim. below frame surface, 0.048/0.108 in (2,50/2,75 mm).

C. Bush, dim. below frame end cover surface, 0.108/0.128 in (2,75/3,25 mm).

D. Bush, frame end cover.

E. Lub. oil transfer plate, L.H. lub. oil filter position.

F. Lub. oil transfer plate, R.H. lub. oil filter position.

G. Balance weight end float dim. 0.0073/0.0148 in (0,186/0,377 mm).

6. Lubricate bushes in frame and end frame cover (see 'A' and 'D', Fig. J.7).

To Fit Balance Weights


A. Engine mounting face.

B. Hole 'C', 49° angle position.

C. Hole dim. 0.354 in (9,0 mm).

D. Gear shaft drive.

E. Hole dim. 0.256 in (6,5 mm).

F. Balance weight assembly position.

7. Position driveshaft/gear to its timed position (see Fig. J.8). Ensure shaft will not move, position balance weights (see Fig. J.8) and ensure that the flats of the weights are in line with each other. Fit frame end cover and lightly hammer location dowels in place and then tighten setscrews to 40 lbf ft (5,5 kgf m) 54 Nm. Ensure balance weight drive gear does not damage bearing when fitted.

8. Fit lubricating oil transfer plate and joint to balancer assembly and tighten flanged bolts to 24 lbf ft (32,5 Nm). Ensure raised symbols are positioned correctly to suit the lubricating oil filter position.

9. If a new frame is used with new lubricating oil direction plugs, ensure the plugs are fitted correctly to suit the filter position and lubricating oil transfer plate symbols (see Fig. J.4/J.5).

10. Fit balance weight cover and tighten setscrews to 7.5 lbf ft (10 Nm).

NOTE: The lubricating oil direction plugs are of different length and have different shape socket heads. The long plug has a square socket and the short plug a hexagon socket. The socket shape will indicate if the plugs and transfer plate are fitted correctly for the lubricating oil flow. Ensure that the long plug is below the machined surface.

To Fit Idler Gear

11. Press in new bearing if necessary. Fit gear and bearing to idler hub and put thrust washer in position. Ensure idler gear hub, or setscrew threads are clean and free from grease. Put 'Loctite 274' compound on the threads and tighten in position to 55 lbs ft (7,5 kgf m) 75 Nm. Check end float of gear 0.003/0.009 in (0,08/0,23 mm).

To Refit and time Balancer to Engine


A. Balance weight flats position.
View looking from front of engine.

Ensure the location dowels are in the cylinder block bores. Set number 1 and 4 pistons at TDC. Locate the balancer unit with the dowels and engage idler gear to crankshaft gear. Look through hole in side of balance weights cover (see Fig. J.9) (later units do not have cover sides) and ensure that the balance weight flats are level with each other and in the centre of the hole (A) with the half round balance weights towards the bottom of the sump. If this position cannot be obtained, the initial timing of the balance weight unit is incorrect (see Fig. J.8). When the timing is correct, secure the balancer unit to the cylinder block and tighten the six flanged bolts to 40 lbf ft (5,5 kgf m) 54 Nm. Fit sump and tighten setscrews to 13 lbf ft (1,8 kgf m) 18 Nm.


1. Lubricating oil transfer plate.

2. Balancer frame.

3. Balancer frame bushes.

4. Driveshaft needle roller bearings.

5. Lubricating oil relief valve assembly.

Centre Mounted Balancer Unit Assembly.


6. Lubricating oil suction pipe.

7. Balance weights.

8. Balance weights gear.

9. Idler gear thrust plate.

10. Idler gear.

11. Idler gear bearing.

12. Idler gear hub.

13. Drive gear and shaft.

14. Lubricating oil pump.