The 1991 Dodge W250 is a workhorse 3/4-ton truck available with either the legendary 5.9L Cummins 12-valve diesel or the 5.9L gas V8. The Cummins is virtually bulletproof but lives behind weak transmissions; the gas V8 has significant bottom-end durability issues.
Automatic Transmission Failure (A727/A518)
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Slipping between gears, especially 2nd to 3rd, Delayed engagement when shifting into Drive or Reverse, Burnt transmission fluid smell, Overheating indicated by fluid discoloration
Fix: The 727/518 automatics weren't built for Cummins torque. Expect full rebuild or replacement. Rebuild takes 12-16 hours including R&R. Upgrade to billet components and add aftermarket trans cooler during rebuild to prevent repeat failure.
Estimated cost: $2,200-3,800
5.9L V8 Bottom End Failure (Rod/Main Bearings)
Common · high severityTypical onset: 120,000-180,000 mi
Symptoms: Low-frequency knocking at idle that increases with RPM, Metallic rattling on cold starts, Sudden loss of oil pressure, Metal flakes/shavings in oil
Fix: The 360 V8 has soft bearing material and marginal oiling under load. Rod knock means full teardown. Most shops recommend short block replacement or complete rebuild with hardened bearings. Plan 24-30 hours labor for engine removal, disassembly, machine work coordination, and reassembly.
Estimated cost: $3,500-5,500
Cummins Fuel System Contamination (Lift Pump Failure)
Occasional · medium severityTypical onset: 60,000-120,000 mi
Symptoms: Hard starting especially when warm, Loss of power under load or at highway speeds, Excessive white smoke on startup, Engine stalling after running fine for 15-20 minutes
Fix: The mechanical lift pump on the Cummins fails and sends debris into the injection pump. Replace lift pump, fuel filter, and drain tank. If caught early, 2-3 hours. If injection pump is damaged, add 6-8 hours and $800-1,200 for a rebuilt P-pump.
Estimated cost: $350-2,000
Transfer Case Linkage Wear (NP241/NP205)
Common · medium severitySymptoms: Inability to shift into or out of 4WD, Grinding when attempting to engage 4WD, Shifter feels loose or won't stay in position, Pops out of 4-Low under load
Fix: Worn shift fork, detent springs, or linkage bushings. External linkage adjustment sometimes helps temporarily but typically needs internal work. Transfer case R&R and rebuild takes 6-8 hours. NP205 is cast iron and more durable but heavier.
Estimated cost: $800-1,400
Transmission Mount and Crossmember Failure
Common · medium severityTypical onset: 100,000-160,000 mi
Symptoms: Clunking when shifting from Park to Drive/Reverse, Excessive driveline vibration at highway speeds, Visible sagging of transmission tailhousing, Transmission hits crossmember on hard acceleration
Fix: The rubber mount deteriorates and the crossmember cracks from heavy towing. Diesel models especially. Replace mount and inspect crossmember for cracks; welding reinforcement is common. 2-3 hours with proper jack support.
Estimated cost: $250-500
Cab and Bed Floor Rust-Through
Occasional · low severitySymptoms: Visible rust holes in cab corners behind doors, Soft spots in floor under carpet/mat, Rust perforation in bed floor and fenders, Water leaking into cab during rain
Fix: More prevalent in salt states. Surface rust becomes structural failure. Cab corner replacement panels available but labor-intensive (8-12 hours per side with bodywork). Bed floor patch panels need welding and undercoating. Not a breakdown issue but kills resale value.
Estimated cost: $1,200-3,500
Buy the Cummins version if you can wrench or have transmission budget; avoid the 5.9L gas unless it's been rebuilt and you see oil pressure gauge pegged above 40 psi hot.
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.