GM bulletin 21-NA-138
What it saysThis service bulletin provides a repair procedure to correct a customer concern of a Squeak, Grind or Clunking Noise from Rear Leaf Springs. NHTSA’s full summary ↓
GM filed this with NHTSA as a service bulletin dated Feb 14, 2025, received Nov 3, 2022, about the suspension — 4 documents under this number. It names 45 model years across Chevrolet and GMC (2016–2025). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
One page for every brand it was filed under. Each brand’s bulletins: Chevrolet · GMC.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThis service bulletin provides a repair procedure to correct a customer concern of a Squeak, Grind or Clunking Noise from Rear Leaf Springs.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 21-NA-138 | Service bulletin | Feb 14, 2025 | 11014358 | PDF, 225 KB |
| 21-NA-138 | Service bulletin | Jul 9, 2024 | 11004990 | PDF, 547 KB |
| 21-NA-138 | Service bulletin | Jan 24, 2023 | 10231503 | PDF, 126 KB |
| 21-NA-138 | Service bulletin | Oct 20, 2022 | 10225662 | not found |
What the document itself lists
Parts the bulletin names
| Part number | Description | Qty | Find it |
|---|---|---|---|
| 87838974 | — | — | |
| 87838975 | — | — |
Labour operation and the time the manufacturer allows
| Operation | Description | Time |
|---|---|---|
| 8080628 | Rear Leaf Spring Insert Replacement | 1 hrs |
Read by machine from the document NHTSA serves (4 pages), read Sep 30, 2026. A part number is shown only where it matches GM’s own catalogue shape, an operation only with its code and time, and a description only where the reader got it whole; anything it could not settle is left out, and the PDF is the record. Times are the manufacturer’s warranty allowances, not a quote. Listings and prices on eBay Motors are the seller’s.
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The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themChevrolet 20 model years
GMC 25 model years
and 5 more on this site: 2020 GMC Sierra 3500HD, 2019 GMC Sierra 3500HD, 2018 GMC Sierra 3500HD, 2017 GMC Sierra 3500HD, 2016 GMC Sierra 3500HD.
A vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
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What owners reported
Source: NHTSA complaint databaseOwners of the 45 model years this bulletin names have filed 4,148 complaints with NHTSA since 2015.
The contact owns a 2016 GMC Sierra. The contact stated that while driving approximately 70- 85 mph, the vehicle was shaking. The stability track warning indicator light was illuminated and flashing on and off. The vehicle was taken to the local dealer but they were unable to duplicate the failure.
2016 GMC Sierra · Suspension · filed with NHTSA Aug 11, 2022
Vibration occurs when driving at highway speed. Vibration can be felt in the steering wheel, drivers seat, and passenger seat. I believe this is related to my vechicles front hub bearing extensions. there was a TSB for this issue on presious model trucks and the same part is used on 2024 models
2024 Chevrolet Silverado 3500HD · Suspension · filed with NHTSA Aug 19, 2024
A complaint is one owner’s account, not a defect finding, and a bulletin is not a recall. Nothing here says this bulletin was issued because of these complaints, or that the repair it describes fixed them. Complaint files on this site begin in 2015.
More bulletins about the suspension
Source: same model, same component group20 other manufacturer communications filed against these GM models under the same component group (suspension), newest first. The eight newest are listed; the rest are on the Chevrolet list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| N252527500 | Service campaign | Nov 12, 2025 | Certain vehicles may have a condition in which the Rear Spring U-bolt fasteners are torqued below specification. Dealers are to torque both… |
| 25-NA-152 | Service bulletin | Oct 3, 2025 | this bulletin advises the tech not to replace the shock for possible air leak, but to replace the air valve on the shock. |
| N252507500 | Service campaign | Sep 17, 2025 | Certain vehicles may have a condition in which the rear lower control arm bolts were not fully torqued. Dealers are to perform a rear wheel… |
| N252508800 | Service campaign | Jun 24, 2025 | Customer Satisfaction Program. Certain vehicles listed above may have improper lubrication of the rear axle assembly. Dealers will replace… |
| PI0281L | Service bulletin | Apr 17, 2025 | This preliminary informational (PI) bulletin provides information to dealership personnel that may be helpful when addressing underbody comp… |
| 19-NA-129 | Service bulletin | Feb 20, 2025 | This technical bulletin provides repair information to correct a customer concern of a squeak and/or clunking noise coming from the rear of… |
| PIT6304A | Service bulletin | Jan 29, 2025 | This Preliminary information communicates a diagnostic Aid from root causing DTC: C1197 sym 92 caused by a pinched air inlet hose to the sus… |
| PIT6304 | Service bulletin | Dec 14, 2024 | This Preliminary information communicates a diagnostic Aid from root causing DTC: C1197 caused by a pinched air inlet hose to the suspension… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Chevrolet and GMC, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is GM 21-NA-138 a recall?
No. A service bulletin is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the 21-NA-138 repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way.
Which vehicles does 21-NA-138 cover?
The manufacturer filed it against 45 model years across 2 brands (Chevrolet and GMC): 2025 Chevrolet Silverado 2500HD, 2024 Chevrolet Silverado 2500HD, 2023 Chevrolet Silverado 2500HD, 2022 Chevrolet Silverado 2500HD, 2021 Chevrolet Silverado 2500HD, 2020 Chevrolet Silverado 2500HD and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.