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Author:

Greg
Scheff

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Title : Replacing the Crankshaft Gear on S13 Engines
Applies To : All S13 Engines

CHANGE LOG
Please refer to the change log text box below for recent changes to this article:
06/24/2025 - Initial Article Release

DESCRIPTION
This document will guide the user through the process of replacing the crankshaft gear for instances where excess oil is seen in
the flywheel bolt holes. Oil can leak from behind the crankshaft gear and out the flywheel bolt holes often times misdiagnosed
as a leaking rear crank seal. A simple way to tell if this is occurring is the flywheel bolts will be very wet with oil, and oil can be
seen puddling in the bolt holes inside the gear.

Figure #1: Excess Oil in the flywheel bolt holes

SYMPTOM(s)
Oil will be seen leaking from the bottom of the flywheel housing area and will coat the inside of the flywheel housing similar to a
rear crank seal leak.

SPECIAL TOOL(s) / SOFTWARE
Tool Description

Tool Number

Comments

M20 Guide Pins (2)

11-729-05-05

Part of 11-729-05 Trans
Service Kit

Rear Crank Seal
Removal Tool
Rear Crank Seal
Installation Tool
Camshaft Locking
Tool

Instructions

12-183-08

Service Manual Link

12-183-09

Service Manual Link

12-357-01

SERVICE PARTS INFORMATION
Kit Description

Part Number

Quantity
Notes
Required

Rear Main Seal Kit

2523699C91

1

Gear Assy, Crankshaft

112911N91

1

Rocker Cover Gasket

118225N1

1

REPAIR STEP(s)

INSPECTION / REMOVAL PROCEDURE:
When inspecting for the source of excess oil coating the inside of the engine flywheel housing, please follow the steps
below
once the transmission and clutch have been removed (flywheel on).

1. Disconnect the batteries if not already done
2. Set the engine to TDC following instructions in the Service Manual
3. Begin removing the flywheel bolts, inspect each one for the presence of excess oil on the bolt shanks
4. If any of the flywheel bolts are wet with excess oil, proceed through this article
5. If no oil is found on the bolts, DO NOT proceed with this instruction and continue with diag to locate the source of the oil
(possible crank seal).
6. Remove the valve cover and install the 12-357-01 camshaft locking tool
7. Before removing the crankshaft seal, clean the oil from inside the flywheel and transmission housings using brake cleaner or
similar degreaser.
This will help to prevent any false indications of an oil leak in the future, and will also keep cleaning debris from entering the
crankcase.
8. Remove the rear crankshaft seal following instructions linked HERE

9. Thread two of the 11-729-05-05 M20 guide studs through the crank gear and into the crankshaft
10. The crank gear should be able to be worked loose with even side to side force and slide off over the two guide studs
11. Clean any oil from the face of the crankshaft after the gear has been removed.

ASSEMBLY PROCEDURE:
12. Clean the mating surface of the new crankshaft gear, and rear crankshaft flange
13. Thread the two M20 guide pins into the crankshaft. Carefully position the new gear over the studs so that the alignment pin
(dowel) in the gear aligns with the hole in the rear of the crankshaft. Make sure the gear fully bottoms out against the crankshaft
and that BOTH the lower oil pump drive gear and upper idler gear are properly meshed. A clean plastic or rubber mallet may be
needed to gently tap the gear side to side evenly to get it to fully seat.

Make certain the lower oil pump gear is properly meshed with the
new crankshaft gear. See figure #4, if the oil pump gear is NOT
meshed, it will snap when the flywheel bolts are torqued resulting
in NO oil pressure on startup.

Figure #4: USE CAUTION That the oil pump to crankshaft gear are fully meshed.

14. Install the new rear crankshaft seal following instructions in the Service Manual
15. Using the two M20 guide pins again, install the flywheel with new bolts as outlined in the Service Manual and torque to specifications.
16. Remove the 12-357-01 camshaft locking tool and install the valve cover per the Service Manual instructions.

17. Finish with installation of the clutch and transmission

WARRANTY INFORMATION
Warranty Claim Coding:
Refer to the Warranty Coding Manual for Group and Noun Codes.

Standard Repair Time(s):
Refer to the SRT Manual for Repair Times

OTHER RESOURCES
Master Service Information Site

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