The 2024 Express carries over the proven but aging full-size van platform. The 6.6L Duramax is solid, but the 6.0L gas V8 and older transmission designs show wear patterns typical of heavy-duty use—expect transmission cooling issues and gasket failures on high-mileage units.
Transmission Oil Cooler Failure (6L80/6L90 Transmissions)
Common · high severityTypical onset: 80,000-140,000 mi
Symptoms: Transmission fluid mixing with engine coolant (strawberry milkshake in overflow tank), Transmission slipping or delayed engagement after cooler breach, Overheating transmission, especially under load or towing
Fix: Replace transmission oil cooler (often integrated into radiator), flush both cooling system and transmission completely, sometimes requires transmission rebuild if contamination went unnoticed. 6-10 hours labor depending on coolant-to-trans damage extent.
Estimated cost: $1,200-$4,500
6.0L Vortec Head Gasket Failure (AFM/DoD Engines)
Occasional · high severityTypical onset: 120,000-180,000 mi
Symptoms: White smoke from exhaust, especially on cold start, Coolant loss with no visible leaks, Rough idle, misfires on one bank, Overheating under load
Fix: Both head gaskets, head resurfacing if warped, new head bolts (TTY), often find cracked heads on high-mileage 6.0L AFM motors. 14-18 hours labor, more if heads need machine work or replacement.
Estimated cost: $2,800-$5,500
AFM/DoD Lifter and Camshaft Failure (6.0L V8)
Common · high severityTypical onset: 100,000-150,000 mi
Symptoms: Loud ticking or tapping noise from engine, especially on startup, Check engine light with P0300-series misfire codes or P0521 (oil pressure), Loss of power, rough running, Metal shavings in oil
Fix: Failed lifters from AFM system collapse; often takes out camshaft lobes. Requires camshaft replacement, all lifters, sometimes pushrod and rocker damage. Many techs delete AFM system during repair. 16-22 hours labor for cam/lifter job.
Estimated cost: $3,500-$6,000
Transmission Mount Deterioration
Common · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Clunking when shifting from Park to Drive or Reverse, Excessive vibration at idle in gear, Visible sagging or cracking of rubber mount
Fix: Replace transmission mount and often engine mounts at same time due to weight and duty cycle. 2-3 hours labor for trans mount, add 1-2 hours if doing engine mounts simultaneously.
Estimated cost: $350-$800
Diesel Exhaust Fluid (DEF) System Issues (6.6L Duramax)
Occasional · medium severityTypical onset: 70,000-120,000 mi
Symptoms: DEF quality warning lights, Speed limitation warning (vehicle will limit to 55 mph), DEF consumption higher or lower than normal, Check engine light with NOx sensor or DEF heater codes
Fix: DEF pump, injector, heater, or quality sensor replacement. Tank contamination requires full system flush. 3-6 hours labor depending on component.
Estimated cost: $800-$2,200
Fuel Pump Failure (6.0L Gas Models)
Occasional · high severityTypical onset: 90,000-140,000 mi
Symptoms: No-start condition, especially when tank is below 1/4, Sputtering or loss of power under acceleration, Whining noise from fuel tank area, Intermittent stalling
Fix: In-tank fuel pump assembly replacement requires dropping 31-gallon midship or rear tank. 3-5 hours labor depending on tank location and rust/corrosion in lines.
Estimated cost: $900-$1,600
Buy the 6.6L Duramax if you need a workhorse; avoid high-mileage 6.0L AFM gas engines unless AFM has been deleted and cooling system is documented clean—transmission cooler contamination is a ticking time bomb.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.