Cadillac bulletin 23-NA-137
What it saysThis service bulletin advises the technician to cut off any extra trans case flange if found contacting the prop shaft. NHTSA’s full summary ↓
Cadillac filed this with NHTSA as a service bulletin dated Aug 8, 2023, received Sep 12, 2023, about the power train. It names 5 model years (2016–2020). 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.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThis service bulletin advises the technician to cut off any extra trans case flange if found contacting the prop shaft.
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| 23-NA-137 | Service bulletin | Aug 8, 2023 | 10242201 | PDF, 1,423 KB |
What the document itself lists
The manufacturer titles it “Information on Transmission Case Flange Interference”.
Labour operation and the time the manufacturer allows
| Operation | Description | Time |
|---|---|---|
| 8486328 | Remove Transmission Flange | 0.3 hrs |
Read by machine from the document NHTSA serves (2 pages), read Sep 30, 2026. A part number is shown only where it matches Cadillac’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 themA 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 5 model years this bulletin names have filed 78 complaints with NHTSA since 2015. 47 of them name Power Train — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.
The contact owns a 2020 Cadillac CT6. The contact stated while driving 65 MPH, the transmission seized, and the vehicle was coasted over to the right side of the roadway while waiting for tow service. A dealer as contacted. The vehicle was towed to the dealer where it was diagnosed with transmission failure. The vehicle was not repaired.
2020 Cadillac CT6 · Power Train · filed with NHTSA Jul 15, 2025 · ODI 11673799
The contact owns a 2020 Cadillac CT6. The contact received notification of NHTSA Campaign Number: 25V148000 (Power Train); however, the part to do the recall repair was unavailable. The contact stated that while his wife was driving at an undisclosed speed, the vehicle jerked before slamming into gear. No warning lights were illuminated.
2020 Cadillac CT6 · Power Train · filed with NHTSA Jun 17, 2025 · ODI 11667446
On July 22, 2025, at 20,245 miles, I brought my 2019 Cadillac CT6-V to an authorized dealer while still under factory warranty, reporting hard shifting during both acceleration and deceleration — the exact symptom described in GM Special Coverage Bulletin N242480631, which addresses a defective transmission control valve subject to…
2019 Cadillac CT6 · Power Train · filed with NHTSA Jul 27, 2026 · ODI 11753001
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 power train
Source: same model, same component group28 other manufacturer communications filed against the Cadillac CT6 under the same component group (power train), newest first. The eight newest are listed; the rest are on the Cadillac list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| N242480631-02 | Service campaign | May 27, 2025 | Certain vehicles listed above, may have a condition where the transmission control valve has worn, resulting in a gradual loss of pressure w… |
| N242480631-01 | Service campaign | May 22, 2025 | Certain vehicles listed above, may have a condition where the transmission control valve has worn, resulting in a gradual loss of pressure w… |
| N242480631 | Service campaign | Mar 7, 2025 | Certain vehicles listed above, may have a condition where the transmission control valve has worn, resulting in a gradual loss of pressure w… |
| PIP5966A | Service bulletin | Mar 2, 2025 | This Preliminary information communicates Diagnostic aids for a no start or DTC'S following a transmission replacement |
| 16-NA-019 | Service bulletin | Feb 12, 2025 | This informational buleltin provides information on Transmission Adaptive Functions and Correcting Low Mileage Harsh Shifts, Slips, or Flare… |
| 09-06-04-026Z | Service bulletin | Jan 9, 2025 | This bulletin provides information on identifying Non-GM Engine Calibrations for Gasoline Engines using the Tech 2 or GDS 2. |
| 21-NA-275 | Service bulletin | Nov 27, 2024 | This service bulletin provides repair information to correct customer concerns of Rear Wheel Lock Up, ABS Event, Loud Bang and a Flashing “D… |
| 08-07-30-035I | Service bulletin | Nov 27, 2024 | This service bulletin provides information on the harmful effects of ethylene glycol in transmission fluid. |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Cadillac, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is Cadillac 23-NA-137 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 23-NA-137 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. Every GM warranty extension on file lists the ones GM has filed.
Which vehicles does 23-NA-137 cover?
The manufacturer filed it against 5 model years: 2020 Cadillac CT6, 2019 Cadillac CT6, 2018 Cadillac CT6, 2017 Cadillac CT6, 2016 Cadillac CT6. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.