How to-Gearbox overhaul including clearances and measurements


b16 mini

Ek9 obsession
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If you are fitting a gear kit, final drive or just some new bearings and synchros then you should be checking your clearances and tolerances, here's a guide to show you how.

Just to note, I shamelessly stole this guide from another site but I'm pretty sure it was stolen from a workshop manual anyway.

Some information is not applicable to our b series gearboxes, I will try and edit and simplify the info when I have the time


Manual Transmission Overhaul





TRANSMISSION DISASSEMBLY
Place clutch housing on supports high enough to keep mainshaft from hitting workbench. If it is necessary to heat transmission case for component removal, DO NOT exceed 212°F (100°C).

Remove back-up light switch and cable bracket. Remove transmission attaching bolts, and disconnect breather tube. Remove 32-mm sealing plug (plug has square hole). Expand snap ring on countershaft ball bearing. Separate transmission housing from clutch housing. See figure 1 and figure 2.


Measure clearance between reverse shift fork and shift piece pin. See figure


Clearance should be .002-.014″ (.05-.35 mm). Service limit is .020″ (.50 mm). If clearance exceeds limit, measure width of “L” groove in reverse shift fork. See figure Width should be .278-.285″ (7.05-7.25 mm). Replace reverse shift fork if width exceeds specification.
Measure clearance between reverse idler gear and reverse shift fork. See figure Clearance should be .020-.043″ (.50-1.10 mm). Service limit is .071″ (1.80 mm). If clearance exceeds service limit, measure width of reverse shift fork pawl opening. Width should be .500-.512″ (12.70-13.00 mm). If width exceeds limit, replace shift fork.
Remove reverse shift fork. Remove reverse idler gear shaft and gear. Remove interlock guide bolt from under clutch housing. Remove shift arm “B” bolt. Tape mainshaft splines for protection. Remove mainshaft and countershaft with shift forks as an assembly from clutch housing. Remove differential assembly.
COMPONENT DISASSEMBLY AND REASSEMBLY

Mainshaft Inspection

Measure clearance between 2nd and 3rd gears. See figure



. If clearance is greater than service limit, measure thickness of 3rd gear. If thickness is within specifications, replace 3rd/4th synchro hub. If thickness is not within specifications, replace 3rd gear.
Measure clearance between 4th gear and spacer collar. If clearance is greater than service limit, measure distance “A” on spacer collar. If distance “A” is greater than specifications, replace spacer collar. If distance “A” is within specifications, measure thickness of 4th gear. Replace 4th gear if thickness exceeds specification. If thickness is within specifications, replace 3rd/4th synchro hub.
Measure clearance between 5th gear and spacer collar. If clearance exceeds specifications, measure distance “B” on spacer collar. If distance “B” is greater than service limit, replace collar. If distance “B” is within specifications, measure thickness of 5th gear. Replace 5th gear if thickness exceeds specifications. If thickness is within specifications, replace 5th synchro hub.
Mainshaft Specifications

2nd-To-3rd Gear Clearance
Standard .002-.008″ (.06-.21 mm)
Service Limit .013″ (.33 mm)
4th Gear-To-Spacer Collar Clearance
Standard .002-.007″ (.06-.19 mm)
Service Limit .12″ (.31 mm)
5th Gear-To-Spacer Collar Clearance
Standard .002-.007″ (.06-.19 mm)
Service Limit .12″ (.31 mm)
3rd Gear Thickness
Standard 1.190-1.192″ (30.22-30.27 mm)
Service Limit 1.187″ (30.15 mm)
4th Gear Thickness
Standard 1.186-1.188″ (30.12-30.17 mm)
Service Limit 1.183″ (30.05 mm)
5th Gear Thickness
Standard 1.119-1.121″ (28.42-28.47 mm)
Service Limit 1.116″ (28.35 mm)
Spacer Collar Height “A”
Standard .899-.900″ (22.83-22.86 mm)
Service Limit .898″ (22.81 mm)
Spacer Collar Height “B”
Standard .926-.928″ (23.53-23.56 mm)
Service Limit .926″ (23.51mm)
Remove synchro hubs using press and steel blocks. Use of jaw-type puller can damage gear teeth.



Disassembly
Use puller to remove bearing. Support 4th gear on steel blocks, and press mainshaft out of 5th synchro hub. Support 3rd gear on steel blocks, and press mainshaft out of 3rd/4th synchro hub. Remove remaining components.

Inspection

Inspect all parts for damage and wear. Replace if necessary. Clean all parts in solvent, then dry and lubricate all parts. Ensure oil passages are free of contamination.
Measure mainshaft at points “D”, “E”, “F” and “G”. See figure. Support mainshaft on “V” blocks. Using dial indicator, measure runout while rotating mainshaft 2 complete revolutions. Replace mainshaft if runout or any part of shaft is not within service limit.
MAINSHAFT BEARING SURFACE SPECIFICATIONS – “D”, “E”, “F” and “G” are measuring points. See figure

“D”
Standard In. (mm).8657-.8661 (21.99-22.00)
Service Limit In. (mm): .8634 (21.93)
“E”
Standard In. (mm): 1.062-1.063 (26.98-26.99)
Service Limit In. (mm): 1.060 (26.93)
“F”
Standard In. (mm): 1.338-1.339 (33.98-34.00)
Service Limit In. (mm): 1.336 (33.93)
“G”
Standard In. (mm): 1.022-1.023 (25.98-25.99)
Service Limit In. (mm): .002 (.05)
Reassembly
Assemble components on mainshaft in reverse order of disassembly. Ensure proper installation of synchro hub, synchro sleeves and ball bearing. See figure.

Mainshaft Thrust Shim Adjustments

Remove thrust shim and oil guide plate from transmission housing. Install 3rd/4th synchro hub, spacer collar, 5th synchro hub (5-speed) or collar (4-speed), and ball bearing on mainshaft. Install mainshaft in transmission housing.
Measure distance “B” between transmission housing end and thrust washer using straight edge and feeler gauge. Measure at 3 locations, and average readings. See figure


Measure distance “C” between clutch housing surface and bearing inner race using straight edge and feeler gauge. Measure at 3 locations, and average readings.
Calculate shim thickness as follows: “B” + “C” – .95 = shim thickness. The number .93 is mid point of flex range of clutch housing bearing spring washer. DO NOT use more than 2 shims. Shims are available in 0.3-mm increments. Shim thickness ranges from .0236″ (.60 mm) to .0709 (1.80 mm). On 1.5L engines, shim diameter is 2.55″ (65 mm). On 1.6L engines, shim diameter is 2.75″ (70 mm). Shim thickness is the same for both shim sizes. Part numbers for 1.5L engines are 23931-PL3-A10 through 23971-PL3-A10. Part numbers for 1.6L engines are 23931-PL3-B00 through 23971-PL3-B00.
Install selected shim in transmission housing. Install spring washer on mainshaft. Clean spring washer and shim thoroughly before installation. Install mainshaft in clutch housing.
Install transmission housing onto clutch housing. Install and tighten bolts. Tap mainshaft with a plastic hammer. Attach Mainshaft Base (07GAJ-PG20130) and Collar (07GAJ-PG20120). Attach Mainshaft Holder (07GAJ-PG20110) to mainshaft. Attach magnetic base to clutch housing, and set dial gauge on top of mainshaft. See Figure. Turn bolt clockwise, and measure clearance. DO NOT turn shaft holder more than 60 degrees after needle of dial indicator stops moving.
Clearance should be .004-.007″ (.11-.18 mm). If reading is not correct, recheck shim thickness.



COUNTERSHAFT MEASUREMENTS

Measure clearance between 1st gear and countershaft. See figure. If clearance exceeds service limit, measure thickness of 1st gear. If thickness is less than service limit, replace 1st gear. If thickness is within specification, replace 1st/2nd synchro hub
Measure clearance between 2nd gear and 3rd gear. If clearance exceeds service limit, measure distance “A” on spacer collar. If distance “A” is less than service limit, replace collar. If distance “A” is within specification, measure thickness of 2nd gear. Replace 2nd gear if thickness is less than service limit. If thickness is within specification, replace spacer collar.
COUNTERSHAFT SPECIFICATIONS

1st Gear-To-Countershaft Clearance
Standard .001-.004″ (.03-.10 mm)
Service Limit .009″ (.22 mm)
2nd Gear-To-3rd Gear Clearance
Standard .001-.004″ (.03-.11 mm)
Service Limit .009″ (.23 mm)
1st Gear Thickness
Standard 1.197-1.198″ (30.41-30.44 mm)
Service Limit 1.195″ (30.36mm)
2nd Gear Thickness
Standard 1.257-1.259″ (31.92-31.97 mm)
Service Limit 1.254″ (31.85 mm)
Spacer Collar Height “A”
Standard 1.261-1.262 (32.03-32.06 mm)
Service Limit 1.260″ (32.01 mm)
Remove synchro hubs using press and steel blocks. Use of jaw-type puller can damage gear teeth.

Disassembly
Using chisel and hammer, raise lock nut tab away from groove in countershaft. Remove lock nut and spring washer. Use bearing puller to remove top ball bearing. Use bearing splitter or appropriate blocks to support 4th gear. Press countershaft out of 4th gear and 5th gear. Support 1st gear, and press countershaft out of 3rd gear. Remove remaining parts.

Inspection

Inspect all parts for damage and wear. Replace if necessary. Clean all parts in solvent, then dry and lubricate all parts. Using press, install 3rd, 4th and 5th gears before lubricating.
Measure the countershaft at points “D”, “E” and “F”. See figure. Support countershaft on “V” blocks. Using dial indicator, measure runout while Rotating countershaft 2 complete revolutions. Replace countershaft if runout or any part of countershaft is not within service limit.
COUNTERSHAFT BEARING SURFACE SPECIFICATIONS – “D”, “E” and “F” are measuring points.

“D”
Standard In. (mm): .983-.984 (24.98-24.99)
Service Limit In. (mm): .981 (24.93)
“E”
Standard In. (mm): 1.416-1.417 (35.98-36.00)
Service Limit In. (mm): 1.415 (35.93)
“F”
Standard In. (mm): 1.181-1.182 (30.00-30.02)
Service Limit In. (mm): 1.179 (29.95)
“G”
Standard In. (mm): 1.022-1.023 (25.98-25.99)
Service Limit In. (mm): .002 (.05)
Runout Limits
Standard In. (mm): .0008 (.020)
Service Limit In. (mm): .0020 (.050)
Reassembly
Assemble components in the reverse order of disassembly. See figure. Ensure friction dampers are properly indexed to mating grooves . Install ball bearing using a press. Install spring washer. Tighten lock nut to 80 ft. lbs. (108 N.m), then stake NEW lock nut tab into groove.

SHIFT FORK ASSEMBLY INSPECTION

Measure clearance between each shift fork and its matching synchro sleeve. Clearance should be .010-.018″ (.25-.45 mm). Service limit is .031″ (.80 mm). If clearance exceeds service limit, measure thickness of shift fork fingers. Finger thickness should be .252-.256″ (6.40-6.50 mm). If either measurement is not within specifications, replace sleeve and shift fork.
Measure clearance between 3rd/4th gear shift fork and shift arm “B”. See figure. Clearance should be .008-.020″ (.20-.50 mm). Service limit is .024″ (.62 mm). If clearance exceeds service limit, measure width of shift arm “B”. Replace shift arm “B” if minimum width is not .508″ (12.9 mm).
SYNCHRO RING AND GEAR


Disassembly
Separate synchro ring and gear. Lubricate and install synchro spring on synchro ring and set aside.

Inspection

Inspect gear teeth for wear, galling, roughness and cracks. Ensure ring and gear turn freely. If replacement is necessary, replace ring and gear as a unit.
Measure ring-to-gear clearance all the way around. See figure. Ensure ring is held evenly against gear while measuring. Ring- to-gear clearance should be .033-.043″ (.85-1.10 mm). Service limit is .016″ (.40 mm). If clearance exceeds limit, replace ring and gear as a unit.
Reassembly
Each synchro sleeve has 3 sets of longer teeth (120 degrees apart) that must be matched with 3 sets of deeper grooves when hub is assembled. See figure.

Installing synchro sleeve with its longer teeth in 1st/2nd synchro hub slots will damage spring ring.

DIFFERENTIAL

FYI: Ring gear bolts have left-hand threads.

Disassembly

Check bearings for wear and rough rotation. If bearings need replacing, use bearing puller to remove bearings from differential carrier.
Remove ring gear. Differential carrier assembly is not serviceable. DO NOT disassemble. If carrier assembly is damaged or backlash is not .002-.006″ (.05-.15 mm), replace the assembly. See figure.
Reassembly
After inspecting condition of carrier assembly, coat all parts with molylube. Mount carrier assembly in Vblocks, with axles inserted into carrier side gears. Mount dial indicator to measure backlash. See figure. Backlash should be .002-.006″ (.05-.15 mm). If backlash exceeds specification, replace differential carrier assembly.

Before differential assembly can be adjusted perform step 1) under Transmission Reassembly

Adjustments

Using 40 mm I.D. driver, ensure differential assembly is seated in clutch housing. Install original thrust shim in transmission housing. See figure. Install transmission housing. DO NOT apply sealer at this time.
Install and torque housing bolts. Measure clearance between thrust shim and outer race in housing. Maximum clearance is .004″ (.10 mm). If not within limits, select proper thrust shim. Disassemble transmission housing and replace original thrust shim with selected thrust shim. Reassemble transmission housing and recheck side clearance.
If differential side clearance is not within specifications, repeat step 2). If differential side clearance is okay, adjustment is complete.
DIFFERENTIAL THRUST SHIM THICKNESS (D16Z6 ENGINE)

Part Number – Thickness
41441-PL3-B00 .039″ – (1.00 mm)
41442-PL3-B00 .043″ – (1.10 mm)
41443-PL3-B00 .047″ – (1.20 mm)
41444-PL3-B00 .051″ – (1.30 mm)
41445-PL3-B00 .055″ – (1.40 mm)
41446-PL3-B00 .059″ – (1.50 mm)
41447-PL3-B00 .063″ – (1.60 mm)
41448-PL3-B00 .067″ – (1.70 mm)
41449-PL3-B00 .071″ – (1.80 mm)
41450-PL3-B00 .041″ – (1.05 mm)
41451-PL3-B00 .045″ – (1.15 mm)
41452-PL3-B00 .049″ – (1.25 mm)
41453-PL3-B00 .053″ – (1.35 mm)
41454-PL3-B00 .057″ – (1.45 mm)
41455-PL3-B00 .061″ – (1.55 mm)
41456-PL3-B00 .065″ – (1.65 mm)
41457-PL3-B00 .069″ – (1.75 mm)
DIFFERENTIAL THRUST SHIM THICKNESS (EXCEPT D16Z6 ENGINE)

Part Number – Thickness
41441-PL3-A00 .039″ – (1.00 mm)
41442-PL3-A00 .043″ – (1.10 mm)
41443-PL3-A00 .047″ – (1.20 mm)
41444-PL3-A00 .051″ – (1.30 mm)
41445-PL3-A00 .055″ – (1.40 mm)
41446-PL3-A00 .059″ – (1.50 mm)
41447-PL3-A00 .063″ – (1.60 mm)
41448-PL3-A00 .067″ – (1.70 mm)
41449-PL3-A00 .071″ – (1.80 mm)
41450-PL3-A00 .041″ – (1.05 mm)
41451-PL3-A00 .045″ – (1.15 mm)
41452-PL3-A00 .049″ – (1.25 mm)
41453-PL3-A00 .053″ – (1.35 mm)
41454-PL3-A00 .057″ – (1.45 mm)
41455-PL3-A00 .061″ – (1.55 mm)
41456-PL3-A00 .065″ – (1.65 mm)
41457-PL3-A00 .069″ – (1.75 mm)
TRANSMISSION REASSEMBLY

Install magnet and reverse lock cam. Place shift arm “A” in clutch housing, then push shift rod through . Install spring washer and shift arm “A” bolt. Install steel ball, spring and spring bolt. Install shift arm “B” into interlock, and set interlock in clutch housing. Insert shift arm shaft “B” in clutch housing. Install shift arm “C” in shift arm “A”, then insert shift arm shaft. Install reverse select retainer and reverse select spring. Install differential assembly.
Insert mainshaft and countershaft into shift forks, and install them as an assembly. Fit tab of interlock assembly into notches of shift forks. Lower mainshaft and countershaft into clutch housing. Install shift arm “B” attaching bolt. Install 1st-2nd select spring and plug bolt. Install interlock guide bolt under clutch housing.
Install reverse idler shaft. Install reverse shift holder. Install oil guide plate and mainshaft thrust shim into transmission housing. Apply sealant to transmission mating surface of clutch housing. Install dowel pins. FYI: This tranny uses no gaskets between major housings. Use Sealant (08718-550000). Assemble housings within 20 minutes after applying sealant, and allow it to cure for at least 30 minutes after assembly before filling it with oil.
Insert snap ring pliers into 32-mm sealing plug hole. Spread snap ring and install onto countershaft ball bearing, then install transmission housing over clutch housing. Ensure to line up shafts. Install 32-mm sealing plug. Install transmission housing bolts in sequence. See figure. Install back-up light switch.
TORQUE SPECIFICATIONS

Back-Up Light Switch – 18 (25) Ft. Lbs. (N.m)
Breather Tube Bolt – 21 (28) Ft. Lbs. (N.m)
Countershaft Lock Nut – 81 (110) Ft. Lbs. (N.m)
Interlock Guide Bolt – 30 (40) Ft. Lbs. (N.m)
Oil Drain Plug 30 – (40) Ft. Lbs. (N.m)
Oil Filler Plug 33 – (45) Ft. Lbs. (N.m)
Plug Bolt 41 – (55) Ft. Lbs. (N.m)
Reverse Lock Cam Bolt – 11 (15) Ft. Lbs. (N.m)
Set Ball
Spring Bolt – 16 (22) Ft. Lbs. (N.m)
“A”, “B” and “C” Bolts – 21 (28) Ft. Lbs. (N.m)
Transmission Housing Bolts – 21 (28) Ft. Lbs. (N.m)
32-mm Sealing Bolt – 18 (25) Ft. Lbs. (N.m)
10-mm Sealing Bolt: 96 (11) INCH lbs. (N.m)
 

Last edited:



b16 mini

Ek9 obsession
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1997 Ek9,1996 ek4 siR, 1972 b18c4 mini
No probs hope it comes in handy, it helped me out when measuring up for the size mainshaft shim I needed.

Hope rvm see's this and sticky's it.
 


b16 mini

Ek9 obsession
Staff member
Donator
Joined
Mar 10, 2008
Messages
3,207
Car(s)
1997 Ek9,1996 ek4 siR, 1972 b18c4 mini
Bump up for sticky??
 

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t3gav

Active Member
Joined
Nov 10, 2011
Messages
735
I don't suppose you have a mainshaft holder @b16 mini ? The calcs are also in a weird format, any idea if it's the same as K series as below?

Calculations

Armed with measurements 1 & 2, calculations can be made to determine the proper 72mm shim thickness to use in the transmission case. Two formulas are given to determine the maximum shim thickness and minimum shim thickness. Armed with the minimum and maximum numbers, Honda recommends the shim that falls between the maximum and minimum.

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

-0.53 + 3.00 - (0.8 + 0.11) = 1.56
-0.53 + 3.00 - (0.8 + 0.17) = 1.50

In this case, the manual would call for a shim of 1.53mm.
 

Last edited:

t3gav

Active Member
Joined
Nov 10, 2011
Messages
735
Found the answer on another site, it's the same as K :) B + C - 0.95 = shim thickness (same thing as above basically half way between the min and max figures).
 


b16 mini

Ek9 obsession
Staff member
Donator
Joined
Mar 10, 2008
Messages
3,207
Car(s)
1997 Ek9,1996 ek4 siR, 1972 b18c4 mini
I don't suppose you have a mainshaft holder @b16 mini ? The calcs are also in a weird format, any idea if it's the same as K series as below?

Calculations

Armed with measurements 1 & 2, calculations can be made to determine the proper 72mm shim thickness to use in the transmission case. Two formulas are given to determine the maximum shim thickness and minimum shim thickness. Armed with the minimum and maximum numbers, Honda recommends the shim that falls between the maximum and minimum.

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

-0.53 + 3.00 - (0.8 + 0.11) = 1.56
-0.53 + 3.00 - (0.8 + 0.17) = 1.50

In this case, the manual would call for a shim of 1.53mm.
I don't have a holder, but I had thought of making one, using the centre of a old clutch to fit over the splines, putting a slit in it so it can be clamped down, then making a clamp to go around it out of some 15 mm plate.

I think if you measure carefully enough it's usually alright anyway, checking it with the holder is probably good for piece of mind though.

I'm not sure what's happened to the format of the calculations, I've noticed things like that in a few threads, I think it may of got screwed up when the forum was updated.

I will have to try and make sense of it again
 


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