NHTSA ID Number: 10205564
Manufacturer Communication Number: 21NA238
Summary
This technical bulletin provides a procedure to inspect the front pump of the transmission for a possible leak.
10 Affected Products
Vehicles
| MAKE | MODEL | YEAR |
CHEVROLET | 3500 | 2020-2021 |
| CHEVROLET | SILVERADO 2500 | 2020-2021 |
| CHEVROLET | SILVERADO 3500 | 2020-2021 |
| GMC | SIERRA 2500 | 2020-2021 |
| GMC | SIERRA 3500 | 2020-2021 |
Condition
Some customers may comment that a transmission fluid leak is coming from the bellhousing inspection cover.
Cause
This condition may be caused by the Automatic Transmission Case Front Cover Seal may be rolled or damaged
Correction
If the leak has been verified to be coming from the front cover seal, replace the Automatic Transmission Case Front Cover Seal and the Torque Converter Fluid Seal.
Service Procedure
Refer to Automatic Transmission Case Front Cover Removal/Install and Torque Converter Fluid Seal Removal/Installation in SI.
Parts Information
| Description | Part Number | Qty |
| SEAL, T/C FLUID | 24293986 | 1 |
| SEAL AUTO TRANS FRT CASE COVER | 24277112 | 1 |
| BOLT, TRNS MNT | 11548787 | 2 |
| NUT, TRNS MNT | 11548414 | 3 |
| SEAL, OUTPUT SEAL SQUARE CUT | 24286193 | 1 |
| FLUID, AUTO TRNS ULV (U.S.) | 19352619 | 8 |
| FLUID, AUTO TRNS ULV (Canada) | 19352620 |
SEOCONTENT-START
Copyright 2021 General Motors LLC. All Rights Reserved.
Service Bulletin Bulletin No.: 21-NA-238
Date: November, 2021
TECHNICAL
Subject: Transmission Fluid Leak Near Bellhousing Area
Brand: Model:
Model Year: VIN:
Engine: Transmission:
from to from to
Chevrolet Silverado
2500HD/3500HD
2020 2021 L5P MGM, MGU
GMC Sierra
2500HD/3500HD
Involved Region or Country North America
Condition Some customers may comment that a transmission fluid leak is coming from the
bellhousing inspection cover.
Cause This condition may be caused by the Automatic Transmission Case Front Cover Seal
may be rolled or damaged
Correction If the leak has been verified to be coming from the front cover seal, replace the Automatic
Transmission Case Front Cover Seal and the Torque Converter Fluid Seal.
Service Procedure
Refer to Automatic Transmission Case Front Cover
Removal/Install and Torque Converter Fluid Seal
Removal/Installation in SI.
Parts Information
Causal
Part
Description Part
Number
Qty
X SEAL, T/C FLUID 24293986 1
X
SEAL AUTO
TRANS FRT
CASE COVER
24277112 1
N/A BOLT, TRNS MNT 11548787 2
N/A NUT, TRNS MNT 11548414 3
N/A
SEAL, OUTPUT
SEAL
SQUARE CUT
24286193 1
N/A FLUID, AUTO
TRNS ULV
19352619
(U.S.)
19352620
(Canada)
8
Page 2 November, 2021 Bulletin No.: 21-NA-238
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation Description Labor Time
8466580 Automatic Transmission Case Front Cover Seal Replacement Use the Published Labor
Operations Time
Version 1
Modified Released November 09, 2021
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.
WE SUPPORT VOLUNTARY
TECHNICIAN
CERTIFICATION
SEOCONTENT-END
1 Associated Document
Manufacturer Communications
Bulletin No.: 21-NA-238
Date: November, 2021
MC-10205564-9999.pdf 501.478KB
- Mobil 1 Synthetic LV ATF HP is a high performance synthetic automatic transmission fluid that delivers extended transmission life with improved thermal stability
- Has outstanding long-term frictional properties to help improve and extend transmission efficiency, smooth shifting performance, and fuel economy
- Exceptional thermal and oxidation stability keep transmissions clean to help provide outstanding performance even under severe driving conditions
- Helps provide reliable lubrication at temperatures down to -78F (-61C), and supports viscosity retention under the most severe high-temperature operating conditions
- Recommended for use in modern high-performance vehicles requiring Dexron HP ATF
- Outstanding long-term frictional properties. Helps to improve and extend transmission efficiency, smooth shifting performance and fuel economy.
- Exceptional thermal and oxidation stability. Keeps transmissions clean to help provide outstanding performance even under severe driving conditions.
- Outstanding film-strength and anti-wear properties. Significant wear reduction which can contribute to long transmission life.
- Excellent low-temperature fluidity. Helps to provide prompt and reliable lubrication at ambient temperatures down to -61º C.
- Exceptional shear stability. Viscosity retention even under some of the severest heavy duty, high temperature operating conditions.
- Mobil 1 Synthetic LV ATF HP 1 Quart
- For use in 95% of vehicles including most CVTs in operation with US registered light duty applications
- High performance conditioning agents prolong seal elasticity to prevent leaks
- Improved durability & transmission life with anti-wear technology to avoid costly repairs
- Enhanced high & low temp performance supports transmission fluid in all weather situations
- Full synthetic formula with advanced additives protects against transmission breakdown better than conventional fluids
- Formulated with full-synthetic base stocks and advanced additive technology to meet the challenging demands of automatic transmissions
- Enhanced anti-shudder protection for smooth shifting and maximum power transfer
- Developed with anti-wear technology to help improve transmission durability
- Engineered with a proprietary blend of base oils and advanced additives to provide better oil flow at low temperatures and greater film protection at higher temperatures
Last update on 2026-05-27 / Affiliate links / Images from Amazon Product Advertising API
This product presentation was made with AAWP plugin.