Bulletin No.: 22-NA-173

Service Bulletin

Date: May, 2024

INFORMATION
Subject:

Brand:

Chevrolet

Information on Transmission Fluid Leak

Model:

Corvette

Model Year:

VIN:

from

to

from

to

2020

2024

—

—

Engine:

Transmission:

All

All

Involved Region or Country

North America, Europe, Israel, Middle East, Japan, Thailand, Australia/New Zealand

Condition

Some customers may comment that transmission fluid can be seen under the vehicle.

Information

The following photos are only for informational purposes and to help guide technicians to
known areas of possible leaks. Testing in the photos used fluorescent dye to aid in better
photography. These transmissions were scrapped after dye was added. At no time
should a technician in the field add dye to the M1L transmission. Technicians should only
follow the trace powder diagnosis procedure recommended in Fluid Leak Diagnosis.

Important: Service agents must comply with all
International, Federal, State, Provincial, and/or
Local laws applicable to the activities it performs
under this bulletin, including but not limited to
handling, deploying, preparing, classifying,
packaging, marking, labeling, and shipping
dangerous goods. In the event of a conflict
between the procedures set forth in this bulletin
and the laws that apply to your dealership, you
must follow those applicable laws.

Copyright 2024 General Motors. All Rights Reserved.

Examples of Transmission Leak Areas of Concern
When performing a leak test always be sure to clean
the transmission thoroughly prior to powder testing.
Make an attempt to protect the transmission labels from
any type of solvent that may be used. Solvents can
erase the print on the labels and make the transmission
difficult to identify. A great opportunity to recreate the
leak after powder application is to perform the
Hydraulic System Flush Procedure in service information document 6412296 multiple times until a leak is
visible. Because of the elevated RPMs in this test and
the vehicle being stationary, always monitor engine
temperature. It may also be necessary to run the
vehicle with the rear wheels spinning on the lift to
reproduce the leak. It will be necessary to disable the
ABS system if this is the case. Make sure the vehicle
has been supported by the lift properly with the recommended lift attachments and that the wheels are clear
of the floor. If the coolant temperature is excessive and
fans continue to run, it may be necessary to allow the
vehicle to cool before continuing testing.

Page 2

May, 2024

Bulletin No.: 22-NA-173

6142752

A leak between sealing plate and Bell Housing.
-

If this leak is found, it will be necessary to replace
the clutch differential housing assembly. Be sure to

also order all the one-time use parts in the service
information repair instructions.

6142966

Leaks at the gasket area between the clutch and differential cover and the main case. There is a gasket in
this area.
-

The gasket in this area is serviceable. Be sure to
follow service information for which parts are onetime use and order these components. Also be
sure to inspect the machined surfaces and attempt
to verify that the leak is actually caused by the
gasket rather than a bolt torque or surface finish
issue that may cause a duplicate repair.

Video (Oil Leak) (SIO# 6460614)

Bulletin No.: 22-NA-173

May, 2024

Page 3

This video above shows transmission case porosity,
issue during testing.

4823455

6142841

This is an area that is often mis-diagnosed as a transmission cooler issue. It was found that in most cases,
leaks in this area are caused by transmission case
porosity under the transmission cooler. Proper
diagnosis in this area would be to inspect the cooler for
any signs of physical damage. If no damage is found,
carefully remove the cooler, and inspect the two (14) Orings for damage and proper sealing. The dye photo
shows a puddle of oil just under the cooler sealing

area in the pocket, the fluid is being pushed through the
case due to material porosity. This concern will require
transmission assembly replacement. This leak can
often be confused with transmission SAV cover and
MCV cover leaks because the leaking fluid from above
tends to get captured by the rails and follow that path.
Be sure to powder test these areas well and with the
understanding that fluid tends to flow down across the
transmission.

Page 4

May, 2024

Bulletin No.: 22-NA-173

6142814

A small crack in the clutch cover area (1) of the input
shaft seal can be mis-diagnosed as an input shaft seal
leak (3). Additional cases have been verified at the
input shaft end plug/seal (2), was damaged during
transmission to engine mating. The input shaft end plug
and the input shaft seal can be serviced separately if a
crack is not witnessed in the clutch cover. If the area is
cracked the clutch differential housing assembly will
need replacement as an assembly. The input shaft end
plug does not come with the clutch differential cover
assembly.

6142818

Porosity concerns with the differential cover. This area
needs to be carefully powder tested to verify the leak is
not associated with the cover seal (16) or the dogbones and seals. Technicians have stated that they
have found the cover double-gasketed when they
confused the metal differential shims with what they
thought were gaskets. All shims need to be re-installed
to retain proper bearing load on differential. If porosity
is found in the cover, the transmission will require
replacement.
Note: Due to a revision in service information, the
engine cradle no longer needs to be removed to
replace the auxiliary canister filter housing. This led to
an update in the labor time study and the labor hours
for this repair have been adjusted to reflect this.

Bulletin No.: 22-NA-173

May, 2024

Page 5

6142744

The auxiliary canister filter can create leaks in several
areas. The most common area is cover seal (20), Oring installation issues after filter replacement. Other
areas of concern can be found at the are O-rings (12)
and (17).

Note: Inspect the cover prior to replacement of the seal
for porosity issues in the O-ring groove area.

The photo above shows the red arrow pointing to a
case porosity issue that was found lying behind the
auxiliary canister housing. With any case porosity
issue, the transmission will require replacement. The
photo below shows the red arrow pointing to the
auxiliary canister filter cover O-ring groove. There have
been known cases with porosity found in the O-ring
groove causing leaks in this area.

6456550

Page 6

May, 2024

Transmission rear cover area leak. (Tremec name
plate):
• If there seems to be a leak in this area, be sure to
clean the area thoroughly. Residual oil can get
trapped between the outer surface and the O-ring.
• After powder testing, if a leak re-occurs, remove
the cover, and inspect the O-ring for damage.

Bulletin No.: 22-NA-173

• The red arrow in the graphic above, points to the
oil dam that may come off when the cover (Tremec
name plate) is removed. If it is removed, it is
necessary to replace the associated O-ring and
align properly with cover prior to re-assembly.
Damage will occur if the oil dam is not aligned to
match the cover.

• If no obvious damage is found with the O-ring, be
sure to inspect the cover itself for porosity issues in
the O-ring groove. It is critical to identify the
difference between a leak and dampness.

6637446

6142979

Bulletin No.: 22-NA-173

May, 2024

Transmission case porosity concerns have been
found in the SAV cover area of the transmission. This is
often the most misdiagnosed leak on this transmission.
The fluid seeps through the case and runs down
between the SAV cover and case to the pan rail, and
often the transmission pan, and gasket get replaced,
then the SAV cover, and finally the transmission. Often

Page 7

these leaks will not develop by just allowing the engine
to run. Usually, the vehicle will need to be lifted safely
on a hoist with the wheels raised to allow the vehicle to
run in gear. This action applies to most porosity leaks.
New Examples of Transmission Leak Areas of
Concern

6636539

Plug leakage and fluid leaking from blind holes will
require transmission replacement.

Page 8

May, 2024

Bulletin No.: 22-NA-173

6636536

Examples of case porosity in front of the SAV cover and
above that left axle stub that may present as an axle
seal leak of SAV cover leak. Powder testing should
allow identification by the technician. If leak is

porosity in these areas the transmission assembly will
need replacement.

Bulletin No.: 22-NA-173

May, 2024

Page 9

6636545

The graphics represent new areas that may exhibit
porosity. The last photos show the difference between
rear case porosity and rear cover (Tremec nameplate)
leaks.
Important: Keep in mind that adding dye to the DCT
transmission is never acceptable. These transmissions
had dye added only to highlight the photos. These
transmissions were cored after testing. If a technician
adds dye to a transmission in the field, it will be
necessary to drain and replace all the fluid at a cost to
the dealer.

Main Shaft Plug
Fluid Tubes and O-rings
MCV (main control valve) Cover and gasket
SAV (solenoid activation valve) Cover and gasket
Canister Filter housing
Canister Filter Cover
Axle Shaft Oil Seals
Cooler and O-rings

Serviceable components for leaks include:

Differential Carrier Cover Seal and O-rings (KIT 1)

Clutch Differential Housing Gasket

Rear Cover (Tremec name plate) and O-ring

Input Shaft Seal
Version

5

Modified

Released August 24, 2022
Revised June 06, 2023 – Changed Engine and Transmission RPOs to All.
Revised October 16, 2023 – Added the 2024 Model Year and Additional Information
under Examples of Transmission Leak Areas of Concern section.
Revised October 30, 2023 – Added Israel, Japan, Thailand to the Involved Region or
Country section and added a Note above the auxiliary canister filter information in the
Examples of Transmission Leak Areas of Concern section.
Revised May 10, 2024 – Added additional information throughout Examples of Transmission Leak Areas of Concern section and Added New Examples of Transmission Leak
Areas of Concern section.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job
properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.

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