2015 MERCEDES-BENZ G-CLASS

Typical onset: 40,000-80,000 mi

Symptoms: Loud rattling or knocking noise from front of engine on cold start, Metallic grinding sound that worsens with RPM, Check engine light with misfire codes, Sudden loss of power or complete engine seizure, Metal shavings in oil during changes

Fix: The M273 balance shaft gear is plastic-coated and disintegrates, sending debris through oil system and destroying bearings, crankshaft, pistons, and cylinder walls. Requires complete engine rebuild or replacement. 40-60 hours labor for full rebuild with machine work, or 25-30 hours for used engine swap. Mercedes issued extended warranty for some VINs but 2015s often excluded.

Estimated cost: $15,000-25,000

Typical onset: 60,000-100,000 mi

Symptoms: Transmission fluid spots under vehicle, Low transmission fluid warning light, Burnt transmission fluid smell, Harsh shifting or delayed engagement when fluid gets low

Fix: The 722.9 seven-speed's oil cooler lines corrode where they connect to the radiator and transmission. Lines themselves rot at crimped fittings. Replace both cooler lines and often the external filter housing while you're there. 3-4 hours labor, straightforward access.

Estimated cost: $800-1,400

Typical onset: 70,000-120,000 mi

Symptoms: Gear oil puddles under front center of vehicle, Whining noise from front diff during turns, Clunking when engaging 4WD, Low fluid causes grinding in extreme cases

Fix: Front output shaft seals on transfer case and front diff input seal fail from age and heat cycling. Often both leak simultaneously. If caught early, just seals—2-3 hours each. If fluid runs low, bearings get damaged and you're looking at full rebuild. Replace both while doing one.

Estimated cost: $600-1,200

Typical onset: 50,000-90,000 mi

Symptoms: Clunking when shifting from Park to Drive or Reverse, Vibration at idle in gear that goes away in neutral, Excessive driveline movement over bumps, Visible separation or cracking of rubber mount

Fix: The rear transmission mount's rubber deteriorates from heat and age, allowing excessive drivetrain movement. Causes uncomfortable shifting feel and can accelerate wear on driveshaft components. Simple replacement, 1.5 hours labor, but requires supporting transmission properly.

Estimated cost: $400-700

Typical onset: null

Symptoms: Fuel smell in cabin or near fuel tank, Raw fuel visible on top of fuel tank, Rough idle or hesitation under acceleration, Check engine light with fuel trim codes

Fix: The fuel filter housing on top of the tank develops cracks at the plastic seams or the o-rings fail. Also sees internal filter element deterioration that sends debris to injectors. Replace entire housing assembly with filter—it's one unit. Tank doesn't need dropping but access is tight. 2-3 hours labor.

Estimated cost: $600-1,000

Typical onset: 80,000-130,000 mi

Symptoms: Vehicle sits low after sitting overnight, Compressor runs constantly or won't shut off, Suspension warning light illuminated, Hissing sound from air struts or compressor, Uneven ride height side-to-side

Fix: Air struts develop leaks at the rubber bellows or internal seals. Compressor wears out from overwork due to leaks or just age. Struts are 2-3 hours each, compressor is 3-4 hours plus system relearn. Often need multiple struts when one fails—they age together. Compressor relay also fails, causing no-start of compressor ($150 part, 0.5 hour).

Estimated cost: $2,000-4,500