2004 MERCEDES-BENZ G-CLASS

Typical onset: 80,000-150,000 mi

Symptoms: sudden metallic knocking or rattling from engine, metal shavings in oil, check engine light with camshaft position codes, complete loss of oil pressure, engine seizure in worst cases

Fix: The M113 engine has a factory defect where balance shaft bolts back out, shearing off and destroying internal components. By the time you hear noise, it's often too late—cam damage, piston damage, crankshaft scoring. Requires full engine teardown at minimum, often complete rebuild or replacement short block. Preventive fix is extracting and installing upgraded aftermarket balance shaft bolts with proper threadlocker before failure (8-12 hours labor). Post-failure rebuild is 30-50 hours depending on damage extent.

Estimated cost: $8,000-18,000

Typical onset: 70,000-120,000 mi

Symptoms: transmission slipping or delayed engagement, harsh shifting between gears, transmission overheating warnings, pink fluid leaking near radiator or frame rails, burnt transmission fluid smell

Fix: The 722.6 transmission relies on external oil cooler lines that crack and leak, or the cooler itself clogs with debris. Loss of cooling destroys clutch packs and valve body. Repair involves replacing cooler lines, external cooler, flushing system, and often replacing conductor plate and valve body if damage occurred. If caught early, just lines and cooler (6-8 hours). If transmission damaged, add rebuild (18-25 hours).

Estimated cost: $1,200-6,500

Typical onset: 60,000-100,000 mi

Symptoms: clunking when shifting from Park to Drive, excessive vibration at idle, harsh engagement into gear, visible transmission sag when inspected from below

Fix: The rubber transmission mount deteriorates and collapses, allowing excessive drivetrain movement. This stresses shift linkage and makes driving unpleasant. Replacement requires supporting transmission and unbolting old mount—straightforward but labor-intensive on the G-Class due to ground clearance and crossmember access (3-4 hours with proper lift).

Estimated cost: $500-900

Typical onset: varies widely

Symptoms: hard starting after sitting, rough idle and hesitation, stalling under load, reduced power and fuel economy, check engine light with lean codes

Fix: The in-tank fuel pump strainer and external fuel filter on these trucks clog from sediment and varnish, especially if vehicle sits. The external filter is accessible but requires working under vehicle and relieving fuel pressure (1.5 hours). In-tank pump replacement requires dropping tank or removing rear interior and cutting access panel (4-6 hours). Often both filter and pump assembly need replacement together.

Estimated cost: $600-1,400

Typical onset: 80,000-130,000 mi

Symptoms: oil spots under front of vehicle, gear oil smell, low fluid levels on dipstick check, whining noise from front end during turns

Fix: Seals on the front differential and transfer case output shafts age and leak. Small seeps are livable but major leaks risk bearing damage from low fluid. Front diff seal replacement requires disconnecting CV axles and pressing new seals (4-5 hours). Transfer case output seal is similar labor. Often done together with fluid service.

Estimated cost: $800-1,600

Typical onset: any mileage

Symptoms: windows moving slowly or not at all, window dropping into door, intermittent window operation, clicking noise from door panel, switch not responding or melted contacts

Fix: Window regulators break plastic sliders and cables fail, causing windows to drop or jam. Switchpacks also fail internally from corrosion. Each window regulator replacement requires door panel removal and riveting or bolting new unit (2-3 hours per door). Switchpack replacement is 1 hour. Not safety-critical but annoying and expensive to fix all four doors.

Estimated cost: $400-800 per window