Nissan Sentra B18 (2020-2025) Service Manual: Mainshaft and Gear

Exploded View

Exploded View

1.	Mainshaft front bearing outer race	2.	Mainshaft front bearing inner race	3.	Mainshaft
4.	1st main gear	5.	1st inner baulk ring	6.	1st synchronizer cone
7.	1st outer baulk ring	8.	1st-2nd coupling sleeve	9.	Insert key
10.	1st-2nd synchronizer hub	11.	2nd outer baulk ring	12.	2nd synchronizer cone
13.	2nd inner baulk ring	14.	2nd main gear	15.	Bushing
16.	3rd main gear	17.	Mainshaft adjusting shim	18.	4th main gear
19.	5th main gear	20.	6th main gear	21.	Mainshaft rear bearing inner race
22.	Mainshaft rear bearing outer race	23.	Snap ring	24.	Mainshaft rear bearing adjusting shim

Disassembly

Disassembly

CAUTION:

• Fix mainshaft in a vise with back plate, and then remove gears and snap rings.

• For removal of snap ring, set snap ring pliers and flat pliers at both sides of snap ring. While expanding snap ring with snap ring pliers, move snap ring with flat pliers.

  

• Disassemble gear components putting direction marks on the parts that never affect any functions.

Remove snap ring (1).

CAUTION:

Do not reuse snap ring.

Remove 6th main gear (1) and mainshaft rear bearing inner race (2), with the following procedure. Set a suitable tool to 6th main gear. Remove mainshaft rear bearing inner race and 6th main gear, using Tool (A).

Tool number

: ST33052000 (  —  )

Remove 4th main gear (1) and 5th main gear (2) with the following procedure. Set a suitable tool to 4th main gear. Remove 5th main gear and 4th main gear, using Tool (A).

Tool number

: ST33052000 (  —  )

Remove mainshaft adjusting shim.

Remove 1st main gear (1), 1st-2nd synchronizer hub assembly (2), 2nd main gear (3), and 3rd main gear (4) with the following procedure. Set a suitable tool to 1st main gear. Remove 3rd main gear, busing, 2nd main gear, 2nd inner baulk ring, 2nd synchronizer cone, 2nd outer baulk ring, 1st-2nd synchronizer hub assembly, 1st outer baulk ring, 1st synchronizer cone, 1st inner baulk ring, and 1st main gear using Tool (A).

Tool number

: ST33052000 (  —  )

Remove insert keys and 1st-2nd coupling sleeve from 1st-2nd synchronizer hub.

Remove mainshaft front bearing inner race (1) with the following procedure. Set a suitable tool to mainshaft front bearing inner race. Remove mainshaft front bearing inner race using Tool (A).

Tool number

: ST33052000 (  —  )

Assembly

Assembly

CAUTION:

• Select mainshaft rear bearing adjusting shim, as per the following procedure when replacing mainshaft adjusting shim, 6th main gear, 5th main gear, or 4th main gear.

  • Replace mainshaft adjusting shim.

    • If new mainshaft adjusting shim is thinner than previous one, offset the thickness difference by selecting thicker mainshaft rear bearing adjusting shim.

    • If new mainshaft adjusting shim is thicker than previous one, offset the thickness difference by selecting thinner mainshaft rear bearing adjusting shim.

  • Replace 6th main gear, 5th main gear, or 4th main gear.

    • Measure the thickness of the main gear used before and the new main gear

    • Increase the thickness of the mainshaft rear bearing adjusting shim, if the difference is smaller than 0.025 mm (0.0010 in).

• Replace transaxle assembly when replacing mainshaft.

• For installation of snap ring, set snap ring pliers and flat pliers at both sides of snap ring. While expanding snap ring with snap ring pliers, move snap ring with flat pliers.

  

• Do not reuse snap ring.

Install mainshaft front bearing inner race (1) using Tool (A).

CAUTION:

Replace mainshaft front bearing outer race and mainshaft front bearing inner race as a set.

Do not reuse mainshaft front bearing inner or outer race.

Tool number

: ST36720030 (  —  )

Apply gear oil to 1st inner baulk ring, 1st synchronizer cone, 1st outer baulk ring, 2nd inner baulk ring, 2nd synchronizer cone, and 2nd outer baulk ring.

CAUTION:

• Replace 1st inner baulk ring, 1st synchronizer cone, and 1st outer baulk ring as a set.

• Replace 2nd inner baulk ring, 2nd synchronizer cone, and 2nd outer baulk ring as a set.

Install insert keys and 1st-2nd coupling sleeve to 1st-2nd synchronizer hub.

CAUTION:

Replace 1st-2nd synchronizer hub and 1st-2nd coupling sleeve as a set.

Install 1st main gear (1), 1st inner baulk ring, 1st synchronizer cone, 1st outer baulk ring, 1st-2nd synchronizer hub assembly (2), 2nd inner baulk ring, 2nd synchronizer cone, and 2nd outer baulk ring.

Install bushing (3) using Tool (A).

Tool number

: ST32102700 (  —  )

Install 3rd main gear (1) and 2nd main gear (2) using Tool (A).

Tool number

: KV32102700 (  —  )

Measure dimension (L) as shown in the figure. Select mainshaft adjusting shim (1) according to the following list, and then install it to mainshaft.

(2)	: Mainshaft
(3)	: 3rd main gear

Unit: mm (in)

Dimension (L)	Mainshaft adjusting shim thickness
147.690 – 147.666 (5.8146 – 5.8136)	1.500 (0.0591)
147.665 – 147.641 (5.8136 – 5.8126)	1.525 (0.0600)
147.640 – 147.616 (5.8126 – 5.8116)	1.550 (0.0610)
147.615 – 147.591 (5.8116 – 5.8107)	1.575 (0.0620)
147.590 – 147.566 (5.8106 – 5.8097)	1.600 (0.0630)
147.565 – 147.541 (5.8096 – 5.8087)	1.625 (0.0640)
147.540 – 147.516 (5.8086 – 5.8077)	1.650 (0.0650)
147.515 – 147.491 (5.8077 – 5.8067)	1.675 (0.0659)
147.490 – 147.466 (5.8067 – 5.8057)	1.700 (0.0669)
147.465 – 147.441 (5.8057 – 5.8048)	1.725 (0.0679)
147.440 – 147.416 (5.8047 – 5.8038)	1.750 (0.0689)
147.415 – 147.391 (5.8037 – 5.8028)	1.775 (0.0699)

Install 4th main gear (1) using Tool (A).

Tool number

: KV32102700 (  —  )

Install 5th main gear (1) using Tool (A).

Tool number

: KV32102700 (  —  )

Install 6th main gear (1) using Tool (A).

Tool number

: KV32102700 (  —  )

Install mainshaft rear bearing inner race (1) using Tool (A).

CAUTION:

Replace mainshaft rear bearing inner race and mainshaft rear bearing outer race as a set.

Tool number

: ST30901000 (NI-26010-01)

Install snap ring.

CAUTION:

Do not reuse snap ring.

Inspection

Inspection

Mainshaft and Gear

Check the following items and replace if necessary.

• Damage, peeling, bend, uneven wear, and distortion of shaft.

• Excessive wear, damage, and peeling of gear.

INSPECTION AFTER DISASSEMBLY

Synchronizer Hub and Coupling Sleeve

Check the following items and replace if necessary.

Breakage, damage, and unusual wear on contact surface of coupling sleeve, synchronizer hub, and insert key.

Coupling sleeve and synchronizer hub move smoothly.

Baulk Ring

Check contact surface of baulk ring cam and insert key for excessive wear, uneven wear, bend, and damage. Replace if necessary.

Bearing

Check bearing for damage and uneven rotation. Replace if necessary.

CAUTION:

• Replace mainshaft front bearing outer race and mainshaft front bearing inner race as a set.

• Replace mainshaft rear bearing inner race and mainshaft rear bearing outer race as a set.