Vertical Misalignment Between Cab and Pickup Box on Driver Side of Vehicle – 2019-2021 Chevrolet Silverado & GMC Sierra

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Service Bulletin Bulletin No.: 20-NA-175
Date: December, 2020
TECHNICAL
Subject: Vertical Misalignment Between Cab and Pickup Box on Driver Side of Vehicle
Brand: Model:
Model Year: VIN: Engine: Transmission:
from to from to
Chevrolet
Silverado 1500 (New
Model – 12th VIN
Digit = 7) – 4WD 2019 2019
All All
Silverado 1500 (New
Model)
Silverado 1500 2020 2021
Silverado 2500HD/
3500HD 2020 2020
GMC
Sierra 1500 (New
Model) 2019 2019
Sierra 1500 2020 2021
Sierra 2500HD/
3500HD 2020 2020
Involved Region or Country North America, Middle East, Israel, Palestine, Chile, Paraguay and Thailand.
Additional Options Crew Cab and Extended Cab Models ONLY
Condition
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Some customers may comment on noticing anywhere from 2 –10 mm (0.08 – 0.4 in.)
vertical misalignment of the body feature line between the cab and the pickup box, on the
driver’s side of vehicle.
Cause The cause of the condition may be pickup box structure variation.
Correction Realign the left side of the cab and install shim washers, following the steps in the
Service Procedure below.
Page 2 December, 2020 Bulletin No.: 20-NA-175
Service Procedure
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1. Verify the condition by visually checking, and
measuring, the body feature line variance, on the
left side of the vehicle.
2. Raise and support the vehicle. Refer to Lifting and
Jacking the Vehicle in SI.
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3. Remove the 3 left side body mount bolts and
washers (1).
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Note: For trucks with running boards, the jack can be
positioned below the running board bracket. For trucks
without running boards, position the jack below the cab
pinch weld and use a wood block to protect the paint,
and sheet metal.
4. Using a jack stand (1), raise the cab high enough
to achieve enough clearance to install the shim
washers between the body of the truck and the top
of each body mount.
Bulletin No.: 20-NA-175 December, 2020 Page 3
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Note: Because there may be variance in how much of
a misalignment is being addressed, varying
combinations of the washer thickness stack-ups may
be used. The washer stack-ups noted below were
effective for our repair, and we felt making use of the
thinner washers helped us better sneak up on a friction
fit to the cab. If the thick washers cannot be installed
with a feeling for a friction fit, using a combination of the
thinner washers may be easier.
Note: In some cases, the installation of the forward
most washer may not be necessary.
5. Install a combination of thick (1) and thin (2) shim
washers to each body mount location, following the
suggested stack-ups below. The rear most location
will have the thickest washer stack-up, and the
stack-ups will gradually reduce, going forward.
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5.1. Install 1 thick, and 2 thin washers, to the
rearward most body mount location, and
partially thread the bolt.
5.2. Install 2 thin washers, to the middle body
mount location, and partially thread the bolt.
5.3. Install 1 thin washer, to the forward most body
mount location, and partially thread the bolt.
6. Remove the jack stand from the cab.
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7. Perform the following procedure before installing
the body mount bolts (1).
7.1. Remove all traces of any of the original
adhesive patch from the bolt threads.
7.2. Clean the threads of the bolts with denatured
alcohol, or equivalent, and allow to dry.
7.3. Apply Threadlocker to the body mount bolts.
Page 4 December, 2020 Bulletin No.: 20-NA-175
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8. Re-torque the 3 left side body mount bolts.
Tighten.
Tighten the bolts to 165 Nm (122 lb ft).
9. Remove the support and lower the vehicle.
10. Verify that the cab alignment condition has been
eliminated.
Parts Information
Contact Fastenal at Phone: (877) 507-7555 or Email:
webhelp@fastenal.com
For sales support outside North America, Email:
intldirectship@fastenal.com
Causal
Part
Description Part
Number
Qty
N/A
Fastenal Low
Carbon Zinc
Finish Steel Extra
Thick Fender
Washer (5/8 ID x
2 1/2 OD x 1/4”)
11103756 Package
of 3*
Fastenal Low
Carbon Zinc
Finish Steel Thick
Fender Washer
(3/4 ID x 2 1/2 OD
x 1/8”)
11103749 Package
of 5*
Threadlocker
12345382
(U.S.)
10953489
(Canada)
As needed
* Most commonly, this repair requires 1 thick, and 5 thin
washers, however different combinations may be found to
be just as effective. Retain any extra washers for future
repairs.
Warranty Information
For vehicles repaired under the Bumper-to-Bumper
coverage (Canada Base Warranty coverage), use the
following labor operation. Reference the Applicable
Warranties section of Investigate Vehicle History (IVH)
for coverage information. Submit the cost of the
required washers as “Net Item Miscellaneous”.
Labor Operation Description Labor Time
1481418* Realign Left Side of Cab to Pickup Box, Install Shim Washers 0.6 hr.
*This is a unique Labor Operation for Bulletin use only.
Version 3
Modified Released – September 02, 2020
Revised October 27, 2020 – Removed Date Breakpoint
Revised December 21, 2020 – Added 2021 Model Year to Silverado/Sierra 1500.

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