Isuzu N-Series. Manual - part 877

7B1-32 MANUAL TRANSMISSION (MZZ)

Disassembly

1. Remove the 6th gear.
2. Use a bearing remover and a press to simulta-

neously remove the following parts.

• Bearing
• Spacer
• Collar
• Reverse gear
• Needle bearing
• Reverse gear inside ring
• Reverse gear outside ring
• Reverse gear block ring
• 1st / reverse clutch hub assembly and sleeve
• 1st gear block ring
• 1st gear outside ring
• 1st gear inside ring
• 1st gear
• Needle bearing

3. Disassemble the 1st / reverse clutch hub assembly

and sleeve.

4. Use a pair of snap ring pliers to remove the snap

ring securing the 4th / 5th clutch hub assembly.

5. Use a bearing remover to simultaneously remove

the 4th / 5th clutch hub assembly, the sleeve, the
4th / 5th block ring, and the 4th gear needle bear-
ing.

6. Disassemble the 4th / 5th clutch hub assembly and

the sleeve.

16. 3rd gear block ring

33. Reverse gear block ring

17. 3rd gear outside ring

34. 1st / reverse clutch assembly and sleeve

N7A1195E

Legend

1. Clutch hub
2. Sleeve
3. Ball
4. Block
5. Spring

N7A0372E

N7A1197E

MANUAL TRANSMISSION (MZZ) 7B1-33

7. Use a pair of snap ring pliers to remove the snap

ring securing the 3rd gear collar.

8. Use a bearing remover to simultaneously remove

the 3rd gear collar, the 3rd gear needle bearing,
the 3rd gear inside ring, the 3rd gear outside ring,
the 3rd gear block ring, the 2nd / 3rd clutch hub as-
sembly, the sleeve, the 2nd gear block ring, the
2nd gear inside ring, the 2nd gear outside ring, and
the 2nd gear needle bearing from the main shaft.

9. Disassemble the 2nd / 3rd clutch hub assembly

and the sleeve.

10. Inspect each of the bearings for roughness, abnor-

mal operating noise, corrosion, internal and exter-
nal damage, and excessive play (in the direction of
the slide). Repair or replace the bearings as re-
quired.

11. Use an inside dial gauge to measure the inside di-

ameter of each of the gears. If the measured diam-
eter exceeds the specified limit, the gear must be
replaced.

Legend

1. Clutch hub
2. Sleeve
3. Ball
4. Block
5. Spring

N7A0372E

N7A1199E

Legend

1. Clutch hub
2. Sleeve
3. Ball
4. Block
5. Spring

Gear inside diameter

mm (in)

Gear

Standard range

Limit

6th

50.009 — 50.025

(1.968 — 1.969)

50.065 (1.971)

5th

48.009 — 48.025

(1.890 — 1.890)

48.065 (1.892)

4th

55.010 — 55.029

(2.165 — 2.166)

55.069 (2.168)

3rd

63.010 — 63.029

(2.480 — 2.481)

63.069 (2.483)

2nd

63.010 — 63.029

(2.480 — 2.481)

63.069 (2.483)

1st

63.010 — 63.029

(2.480 — 2.481)

63.069 (2.483)

Reverse

63.010 — 63.029

(2.480 — 2.481)

63.069 (2.483)

N7A0372E

7B1-34 MANUAL TRANSMISSION (MZZ)

12. Use a dial gauge to measure the main shaft deflec-

tion (curvature). If the deflection exceeds the spec-
ified limit, the shaft must be replaced.

13. Inspect the synchromesh mechanism. Use an oil

stone or a pencil grinder to correct light stepping
and other minor imperfections.

14. Use a thickness gauge to measure the gaps be-

tween the block ring and the dog gear. If the gap
exceeds the specified limit, the block ring must be
replaced.

Main shaft deflection

mm (in)

Standard

Limit

0.015 (0.001)

0.1 (0.004)

N7A1201E

N7A1202E

Block ring and dog gear gap

mm (in)

Gear

Standard range

Limit

4th / 5th / 6th

1.03 — 2.60

(0.04 — 0.10)

0.50 (0.02)

2nd / 3rd

1.00 — 2.50

(0.04 — 0.10)

0.50 (0.02)

1st / Reverse

1.00 — 2.50

(0.04 — 0.10)

0.50 (0.02)

N7A1203E

N7A1204E

MANUAL TRANSMISSION (MZZ) 7B1-35

15. Inspect the clutch hub and sliding sleeve contact

surfaces for wear and/or damage.

16. Inspect the spline interior and groove for wear and/

or damage.

17. Measure the spline play in the direction of rotation

(above the clutch hub outside circumference). If
the play exceeds the specified limit, the spline must
be replaced.

18. Measure the gaps (A) at the clutch hub and the

protrusion of the block ring using a thickness
gauge.

• If the measurements exceed the limits, replace the

block and clutch hub.

Reassembly

1. Clean all the parts.
2. Place the main shaft in a vise. The long end of the

spline must be facing down.

3. Install the block and spring to the 2nd / 3rd clutch

hub.

4. Insert the 3 balls into the 3 insert grooves inside the

sleeve. Position the balls carefully to set the phase.

Legend

1. Block ring
2. Outside ring
3. Inside ring

Spline play

mm (in)

Standard

0 — 0.16 (0 — 0.01)

N7A1205E

N7A1206E

Block and clutch hub gap

mm (in)

Gear

Limit

5th / 4th

6th

4.30 — 4.70

(0.17 — 0.19)

1st / Reverse

3rd / 2nd

3.30 — 3.70

(0.13 — 0.15)

Legend

1. Block ring
2. Clutch hub

N7A1209E

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