M/T Mainshaft Thrust Clearance Adjustment

Special Tools Required
Mainshaft holder (  07GAJ-PG20110)

Mainshaft base (  07GAJ-PG20130)



1.Remove the 72 mm shim (A) and oil guide plate M from the transmission housing (B).

2.Install the 3rd/4th synchro hub (A), the distance collar (B), the 5th/6th synchro hub (C), distance collar (D), and ball bearing (E) on the mainshaft (F), then install the assembled mainshaft in the transmission housing (G).

3.Install the washer (H) on the mainshaft.

4.Measure distance (1) between the end of the transmission housing and washer with a straight edge and vernier caliper. Measure at three locations and average the reading.

5.Measure distance (2) between the end of the clutch housing (A) and bearing inner race (B) with a straight edge and depth gauge. Measure at three locations and average the readings.

Shim Selection Formula:


6.Select the proper 72 mm shim from the chart. Follow the example below, and use the measurements you made in steps 4 and 5:

(Basic Formula)
(1) + (2) - (0.8 + 0.11) = shim thickness (maximum) 
(1) + (2) - (0.8 + 0.17) = shim thickness (minimum) 


  • Add distance (2) (step 5) to distance (1) (step 4).
  • 0.8 mm (0.031 in): Spring washer, a dimension in the installation.
  • 0.11 mm (0.004 in): Minimum thrust clearance.
  • 0.17 mm (0.007 in): Maximum thrust clearance.

(For example)
2.32 + 0.15 - (0.8 + 0.11) = 1.56 mm (0.061 in.) 
2.32 + 0.15 - (0.8 + 0.17) = 1.50 mm (0.059 in.) 


Take the middle value of the minimum value and the maximum value, and select the 1.53 mm (0.060 in.) shim.

72 mm Shim
 Part Number Thickness 
A 23931-P21-000 0.60 mm (0.024 in.) 
B 23932-P21-000 0.63 mm (0.025 in.) 
C 23933-P21-000 0.66 mm (0.026 in.) 
D 23934-P21-000 0.69 mm (0.027 in.) 
E 23935-P21-000 0.72 mm (0.028 in.) 
F 23936-P21-000 0.75 mm (0.030 in.) 
G 23937-P21-000 0.78 mm (0.031 in.) 
H 23938-P21-000 0.81 mm (0.032 in.) 
I 23939-P21-000 0.84 mm (0.033 in.) 
J 23940-P21-000 0.87 mm (0.034 in.) 
K 23941-P21-000 0.90 mm (0.035 in.) 
L 23942-P21-000 0.93 mm (0.037 in.) 
M 23943-P21-000 0.96 mm (0.038 in.) 
N 23944-P21-000 0.99 mm (0.039 in.) 
O 23945-P21-000 1.02 mm (0.040 in.) 
P 23946-P21-000 1.05 mm (0.041 in.) 
Q 23947-P21-000 1.08 mm (0.043 in.) 
R 23948-P21-000 1.11 mm (0.044 in.) 
S 23949-P21-000 1.14 mm (0.045 in.) 
T 23950-P21-000 1.17 mm (0.046 in.) 
U 23951-P21-000 1.20 mm (0.047 in.) 
V 23952-P21-000 1.23 mm (0.048 in.) 
W 23953-P21-000 1.26 mm (0.050 in.) 
X 23954-P21-000 1.29 mm (0.051 in.) 
Y 23955-P21-000 1.32 mm (0.052 in.) 
Z 23956-P21-000 1.35 mm (0.053 in.) 
AA 23957-P21-000 1.38 mm (0.054 in.) 
AB 23958-P21-000 1.41 mm (0.056 in.) 
AC 23959-P21-000 1.44 mm (0.057 in.) 
AD 23960-P21-000 1.47 mm (0.058 in.) 
AE 23961-P21-000 1.50 mm (0.059 in.) 
AF 23962-P21-000 1.53 mm (0.060 in.) 
AG 23963-P21-000 1.56 mm (0.061 in.) 
AH 23964-P21-000 1.59 mm (0.063 in.) 
AI 23965-P21-000 1.62 mm (0.064 in.) 
AJ 23966-P21-000 1.65 mm (0.065 in.) 
AK 23967-P21-000 1.68 mm (0.066 in.) 
AL 23968-P21-000 1.71 mm (0.067 in.) 
AM 23969-P21-000 1.74 mm (0.069 in.) 
AN 23970-P21-000 1.77 mm (0.070 in.) 
AO 23971-P21-000 1.80 mm (0.071 in.) 

7.Install the 72 mm shim (A) selected and oil guide plate M in the transmission housing (B).

8.Throughly clean the spring washer (A) and washer (B) before installing them on the ball bearing (C). Note the installation direction of the spring washer.

9.Install the mainshaft in the clutch housing.

10.Place the transmission housing over the mainshaft and onto the clutch housing.

11.Tighten the clutch and transmission housings with several 8 mm bolts.

NOTE: It is not necessary to use sealing agent between the housings.

12.Lightly tap on the mainshaft with a plastic hammer.

13.Attach the special tool to the mainshaft as follows:

  • Back-out the mainshaft holder bolt (A) and loosen the two hex bolts (B).
  • Fit the holder over the mainshaft so its lip is towards the transmission.
  • Align the mainshaft holder¢s lip around the groove at the inside of the mainshaft splines, then tighten the hex bolts.

14.Seat the mainshaft fully by tapping on its end with a plastic hammer.

15.Thread the mainshaft holder bolt in until it just contacts the wide surface of the mainshaft base.

16.Zero a dial gauge (A) on the end of the mainshaft.

17.Turn the mainshaft holder bolt (B) clockwise; stop turning when the dial gauge (A) has reached its maximum movement. The reading on the dial gauge is the amount of mainshaft end play.

NOTE: Do not turn the mainshaft holder bolt more than 60 degrees after the needle of the dial gauge stops moving. Appling more pressure with the mainshaft holder bolt this may damage the transmission.

18.If the reading is within the standard, the clearance is correct. If the reading is not within the standard, recheck the shim thickness.

Standard: 0.11-0.17 mm (0.004-0.007 in.)