Mercedes-Benz · Known Issues
2018 Mercedes-Benz G-Class Problems: 8 Known Issues
2018 model year · 2,300+ owner reports · Updated September 2026
2018 · All trims · All engines
Choose the year and equipment for your written issues and visual request.
2018 model year · 2,300+ owner reports · Updated September 2026
2018 · All trims · All engines
Choose the year and equipment for your written issues and visual request.
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According to Au7o's analysis of 2,300+ owner reports, the 2018 Mercedes-Benz G-Class has 8 documented known issues, with 2 rated critical. The most serious are Front Axle Seal Leak ($600-$1,500 repair) and M157 5.5L Biturbo V8 Cylinder Scoring and Camshaft Adjuster Wear (Pre-Facelift G 63) ($800-$20,000 repair). The most commonly reported issue is Steering Damper Wear Causing Wander and Vibration with 890 owner reports. Across all issues with published estimates, repair costs range from $200 to $20,000. DIY maintenance guides at au7o.io.
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According to Au7o's analysis of 2,300+ owner reports, the 2018 Mercedes-Benz G-Class has 8 documented issues. The most frequently reported are: Front Axle Seal Leak, M157 5.5L Biturbo V8 Cylinder Scoring and Camshaft Adjuster Wear (Pre-Facelift G 63), Steering Damper Wear Causing Wander and Vibration. Of these, 2 are rated critical and should be addressed promptly.
The 2018 Mercedes-Benz G-Class has 8 known issues documented across 2,300+ owner reports. 2 issues are rated critical: Front Axle Seal Leak and M157 5.5L Biturbo V8 Cylinder Scoring and Camshaft Adjuster Wear (Pre-Facelift G 63). Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.
Repair costs for known Mercedes-Benz G-Class issues range from $200 to $20,000, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, Front Axle Seal Leak, typically costs $600-$1,500 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.
The front differential axle seals on the W463 G-Class are prone to leaking gear oil, particularly on higher-mileage vehicles. Oil seeps past the worn seals onto the brake components, potentially contaminating brake pads and reducing braking effectiveness. The solid axle design ma… Repairs typically run $600-$1,500. Severity: high.
The 5.5L M157 biturbo V8 used in the W463 AMG G 63 before the 2019 redesign is documented for cylinder wall scoring/scuffing at higher mileage plus weaknesses in timing-chain components and camshaft (VVT) adjusters. The camshaft adjuster magnets/solenoids meter oil to the VVT and… Repairs typically run $800-$20,000. Severity: high.
Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.
The recirculating ball steering system on W463 G-Class models relies on a steering damper that wears out over time, causing excessive highway wander, steering wheel vibration at speed, and a vague on-center feel. The solid front axle design amplifies these symptoms compared to in… Repairs typically run $300-$800. Severity: medium.
The transfer case on newer G-Class models develops fluid leaks at the output shaft seals, particularly where the driveshafts connect. The leak typically starts as a slow seep and worsens over time, eventually leading to low fluid levels and potential transfer case damage if not a… Repairs typically run $500-$1,200. Severity: medium.
The hand-built W463 body (Magna Steyr, Graz) is widely documented for rust because the panel metallurgy and rust-proofing are little changed from the late-1970s design. Common corrosion sites are the rear tailgate (especially the lower section around the spare-tire mount), door b… Repairs typically run $400-$8,000. Severity: medium.
European-market diesel G-Class models with the OM642 3.0L V6 (G 320 CDI / G 350 CDI / G 350 d) commonly develop oil leaks from the engine oil cooler seals seated in the valley of the engine block. The original orange seals harden from heat and shrink, allowing oil to weep down th… Repairs typically run $600-$1,800. Severity: medium.
On diesel G-Class models with the OM642 V6, the plastic intake-manifold swirl flap linkage becomes brittle and snaps, and the swirl-flap actuator motor can fail (often after being contaminated by oil weeping from the turbo inlet seal). The broken plastic rods can also be drawn in… Repairs typically run $200-$900. Severity: medium.
Both the older COMAND NTG5 system and the newer MBUX system in the G-Class experience random freezes, black screens, and spontaneous reboots. The harsh vibration environment of the G-Class body-on-frame chassis may contribute to connection issues at the head unit. Navigation, aud… Severity: low.