AI Damage2018 Mercedes-Benz GLS 550 reliability: common problems
Owners of the 2018 Mercedes-Benz GLS 550 filed 6 complaints with NHTSA, most often about powertrain and electrical system. The maker issued 78 service bulletins for this year. Details by component below, with sources.
Key figures
- Owner complaints
- 6
- Technical service bulletins (TSB)
- 78
What fails most often
- 1 Powertrain 17% of all complaints
- 2 Electrical system 17% of all complaints
- 3 Suspension 17% of all complaints
- 4 Visibility 17% of all complaints
- 5 Service brakes 17% of all complaints
- 6 Seat belts 17% of all complaints
- Powertrain: 1 complaints (17% of all); manufacturer bulletins for this component: 22.
- Electrical system: 1 complaints (17% of all); manufacturer bulletins for this component: 21.
- Suspension: 1 complaints (17% of all); manufacturer bulletins for this component: 6.
- Visibility: 1 complaints (17% of all); manufacturer bulletins for this component: 3.
- Service brakes: 1 complaints (17% of all); manufacturer bulletins for this component: 1.
Symptoms owners describe
How many of the 6 NHTSA complaints mention each symptom (automatic count from complaint text; one complaint can mention several).
Components owners complain about
| Component | Owner complaints | involving a crash | Technical service bulletins (TSB) |
|---|---|---|---|
| Powertrain | 1 | 0 | 22 |
| Electrical system | 1 | 0 | 21 |
| Suspension | 1 | 0 | 6 |
| Visibility | 1 | 0 | 3 |
| Service brakes | 1 | 0 | 1 |
| Seat belts | 1 | 0 | 0 |
| Exterior lighting | 0 | 0 | 12 |
| Structure | 0 | 0 | 6 |
| Fuel/propulsion system | 0 | 0 | 4 |
| Engine and cooling | 0 | 0 | 3 |
| Backover prevention | 0 | 0 | 1 |
| Engine | 0 | 0 | 1 |
| Equipment | 0 | 0 | 1 |
| Fuel system | 0 | 0 | 1 |
What owners report
Short excerpts of NHTSA complaints in the original wording. These are owner statements not verified by NHTSA; personal data removed.
The contact stated while driving at various speeds, the vehicle made an abnormal clicking sound when making a right turn, and an abnormal ticking sound at startup. There was no warning light illuminated.
Water collects at the front row floor at driver and passenger sides
The brake warning indicator light was illuminated. The contact stated that the brake pad on one side of the disc was completely worn, and the other side of the disc was like new with a full thick pad. The vehicle was taken to the local dealer and the contact was informed that the brake rotor needed to be replaced.
Seatbelt had tightened and not released when my body moves. Brakes are not applied. Typically during driving I'm small enough to maneuver my hand down to release red seat belt button. I've had to stop my vehicle 5-10 times to release belt.
While in motion on a highway in stop and go traffic, car shifted itself from drive to neutral without any driver input. All indicator lights on dash turned on. Driver unable to shift from neutral back to drive to regain control of vehicle. Driver could only shift to park.
When owners complained
NHTSA complaints by filing year. The peak shows at what age the problems show up most.
Comparison
By complaint count this model year ranks 12,234 of 32,257 model years in the NHTSA data (top 38% most complained about).
On average one model year of the GLS 550 has 5 complaints (3 years in the data). This year has 6, above average.
What to check before buying
- Powertrain. Shift quality under load, harsh shifts, transmission codes, CV joints.
- Electrical system. Scan all modules, test the battery and alternator, inspect connectors near the impact zone.
- Suspension. Wheel alignment, control arms, subframe, even tire wear.
- Visibility. Wipers, mirrors, defrosters, cracked glass.
Manufacturer service bulletins
Bulletin titles as filed with NHTSA.
- Complaint Clanking noise from the area of the speakers in the doors
Cause Under analysis. Remedy To narrow down the cause, first of all remove the door trim. • If the noise continues to occur even with the door trim removed, then continue the diagnosis working towards the speaker and…
- Complaint Customer complaints relating to automatic transmission 725.0 (NAG3 Classic /9G‑TRONIC automatic…
Complaint Customer complaints relating to automatic transmission 725.0 (NAG3 Classic /9G‑TRONIC automatic transmission) and 725.1 (NAG3 facelift/9G‑TRONIC automatic transmission facelift) For faster, more effective and…
- Complaint Repeat workshop visit for vehicle vibration while braking from 60MPH. NOTE
Although the symptom is similar to a tire or wheel vibration, it is usually readily noticeable that it is distinctly different if it happens at all times or only while braking. Cause Although the cause of the vibration…
- Complaint Only vehicles with a variable transfer case are affected
This can be identified through control unit N45 or N15/7 in the quick test. When accelerating with light load, vibrations or jolting sensation may come from the drivetrain. It may be mistaken for a harsh shift. Cause…
- Complaint Customer complaints relating to automatic transmission 725.0 (NAG3 Classic / 9G‑TRONIC automatic…
Complaint Customer complaints relating to automatic transmission 725.0 (NAG3 Classic / 9G‑TRONIC automatic transmission) and 725.1 (NAG3 facelift/9G‑TRONIC automatic transmission facelift) For faster, more effective…
- Complaint During part of the steering movement, it feels heavier or more difficult to steer in the same…
Complaint During part of the steering movement, it feels heavier or more difficult to steer in the same spot every time. OR Rattling, humming, dry sliding/gravel noise from the electric steering system when steering…
- Dear Mercedes-Benz Owner
In our continuing efforts to ensure the proper performance of Mercedes-Benz products and to enhance the satisfaction of our customers, Mercedes-Benz USA is extending the warranty coverage for the Diagnostic Module for…
- Complaint A popup is seen on the HU with the message "data connection temporarily not available"
Potentially affected functionalities in NTG4.5, NTG5 1.Weather 2.Local Search 3.IP Radio 4.Send2Car 5.Speech Detection Service 6.Navigation 7.iHeartRadio 8.Traffic Cams Cause MB Apps is sundowned for all vehicles with…
- Complaint This document is intended as a pre-case diagnostic reference for transmission related concerns
It will also ensure that if a case is necessary, all supporting documentation is available. This should not be used on its own as justification for creating a TIPS case. Cause The root cause will vary depending on the…
- Complaint Mercedes-Benz USA is currently experiencing limited availability of transmission fluid…
Complaint Mercedes-Benz USA is currently experiencing limited availability of transmission fluid specification ATF 236.17 due to a global supply constraint. 236.17 ATF 1L and 5L (PNs: A002989060312 and A002989060313)…
- This NCU replaces the prior NCU issued on May 15, 2025, and contains additional MY 2023 and MY 2024…
This NCU replaces the prior NCU issued on May 15, 2025, and contains additional MY 2023 and MY 2024 vehicles which are highlighted below. In our continuing efforts to ensure the proper performance of Mercedes-Benz…
- Single throttle lift-off clunking noise from the side shaft when moving off (audible at the outboard end)
The noise is heard once in each instance when changing direction of travel. Note: Sound file in attachment Cause If the complaint is eliminated by experimentally loosening the outboard collar nut (by 1 turn), the…
NHTSA lists 78 bulletins for this year; the 12 newest are shown here.
Other years of this model
Questions and answers
What are the most common problems with the 2018 Mercedes-Benz GLS 550?
Owner complaints to NHTSA most often mention: powertrain, electrical system, suspension. Total complaints: 6. The most frequent symptoms in complaint texts: warning lights, check engine (33%), knocking, grinding or other noise (17%), seat belts (17%).
How many service bulletins (TSB) were issued for the 2018 Mercedes-Benz GLS 550?
NHTSA lists 78 manufacturer service bulletins for this year. A bulletin tells dealers how to diagnose or fix a known issue; it is not a recall.
Should I buy a 2018 Mercedes-Benz GLS 550 from a US auction?
Owner complaints describe defects, not crash damage. Before bidding, check the components listed above and review the lot photos: VinWind builds a report of visible and hidden damage by VIN.
Other 2018 models
Read also
Sources: public NHTSA data (USA): service bulletins and owner complaints; YouTube: links to videos credited to their authors. Complaints are owner statements not verified by NHTSA, and describe defects rather than crash damage. Data updated 2026-11-06.