The 2020 Ram 2500 is a workhorse with two very different personalities: the 6.4L Hemi is generally reliable but thirsty, while the 6.7L Cummins has specific weaknesses in emissions systems and lift pump longevity. The Aisin transmission behind the diesel is stout, but the 68RFE behind the Hemi sees cooler and mount failures.
Transmission Oil Cooler Failure (68RFE - Hemi trucks)
Common · high severityTypical onset: 60,000-110,000 mi
Symptoms: Transmission fluid mixing with coolant, pink or milky coolant in overflow tank, Transmission overheating warnings on dash, Hard shifts or loss of gears after coolant contamination
Fix: Replace cooler, flush both cooling system and transmission completely. If contamination went unnoticed, expect internal trans damage requiring rebuild. 4-6 hours labor for cooler only, 12-18 hours if transmission needs rebuild.
Estimated cost: $800-1,200 cooler only; $3,500-5,500 with rebuild
Cummins CP4 Lift Pump Failure (Diesel)
Occasional · high severitySymptoms: Hard starting or extended crank time, Loss of power under load, limp mode, Metal shavings in fuel filter, fuel system contamination when pump grenades
Fix: CP4 pump itself is the weak link—when it fails catastrophically, metal debris circulates through entire fuel system. Requires pump, injectors, fuel lines, tank cleaning. Preventive upgrade to aftermarket lift pump recommended. 8-12 hours labor for pump only, 20-30 hours for full contamination cleanup.
Estimated cost: $1,500-2,500 pump replacement; $8,000-12,000 full system contamination
DEF System Faults and NOx Sensor Failures (Diesel)
Common · medium severityTypical onset: 50,000-90,000 mi
Symptoms: Check engine light with P20EE or P2201 codes, DEF quality warnings on dash, Derate warnings, eventual speed limitation if ignored
Fix: Upstream or downstream NOx sensors fail, DEF injector clogs, or DEF pump quits. Diagnosis takes 1 hour, sensor replacement 2-3 hours, DEF injector or pump 3-4 hours. Use only quality DEF and don't let it sit in tank for months.
Estimated cost: $600-1,200 sensors; $1,200-2,000 injector/pump
EGR Cooler Clogging (6.7L Cummins)
Occasional · medium severityTypical onset: 80,000-140,000 mi
Symptoms: Loss of power, black smoke under load, Check engine light with EGR flow codes, Excessive soot buildup visible in intake
Fix: EGR cooler plugs with soot, especially on trucks doing short trips or excessive idling. Delete kits are illegal for street use; proper fix is cooler replacement and cleaning intake. 6-8 hours labor. Some owners opt for more frequent EGR cleaning intervals.
Estimated cost: $1,800-2,800
Transmission Mount Failure (All)
Common · low severityTypical onset: 40,000-80,000 mi
Symptoms: Clunk when shifting from Park to Drive or Reverse, Vibration at idle in gear, Visible sagging or torn rubber on mount inspection
Fix: Rubber transmission mount deteriorates, especially on trucks used for towing. Simple replacement, 1.5-2 hours labor. Aftermarket polyurethane mounts last longer but transmit more vibration.
Estimated cost: $250-450
Backup Camera Failures and Mirror Defects
Occasional · low severitySymptoms: Backup camera image freezing, going black, or distorted lines, Mirror glass detaching from power-fold assemblies, Camera lens fogging internally
Fix: Recall issued for camera harness issues; dealers reflash module or replace camera. Mirror glass separates from heating element on power-fold mirrors, requires mirror cap replacement. 1-2 hours labor.
Estimated cost: $150-400 camera; $300-600 mirror assembly
Front Axle Disconnect Actuator Failure (4WD)
Occasional · medium severityTypical onset: 50,000-100,000 mi
Symptoms: 4WD will not engage, dash indicator blinks, Grinding noise from front end when attempting 4WD engagement, Service 4WD system message on display
Fix: Electric actuator on front axle seizes or motor burns out. Requires actuator replacement, sometimes with updated revision. 2-3 hours labor, but access is tight.
Estimated cost: $500-900
Buy the diesel if you tow heavy and can handle emissions-system maintenance costs; buy the Hemi if you want simpler ownership and don't need maximum torque—but budget for the trans cooler eventually on either.
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.