The 1991 Dodge Ram W350 is a heavy-duty 1-ton 4x4 built on Dodge's last pre-redesign platform. The Cummins diesel is legendary for longevity but demands attention to cooling and injection systems, while the 5.9L gas V8 is simpler but prone to wear issues in high-mileage or overloaded trucks.
Automatic Transmission Overheating and Cooler Failure (A727/A518)
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Burnt transmission fluid smell or dark brown/black fluid, Slipping or delayed engagement, especially when hot, External transmission cooler leaking at radiator or lines, Overheating during towing or heavy loads
Fix: Replace external transmission oil cooler, flush system, and install auxiliary cooler if towing regularly. Often requires transmission service or rebuild if damage already occurred. 4-6 hours labor for cooler replacement alone, 12-20 hours if transmission needs rebuild.
Estimated cost: $600-1,200 for cooler and service, $2,500-4,000 if transmission rebuild required
Cummins 12-Valve Injection Pump Failure (Diesel Models)
Occasional · high severityTypical onset: 150,000-250,000 mi
Symptoms: Hard starting or extended cranking, especially cold, Loss of power under load or at highway speeds, Black smoke from exhaust, rough idle, Fuel in oil (dilution) from internal pump seal failure
Fix: Replace or rebuild Bosch VE injection pump. Requires removal, timing reset, and fuel system bleeding. Common to upgrade to P7100 pump. 8-12 hours labor for R&R and timing.
Estimated cost: $1,800-3,500 depending on rebuild vs replacement
Front Dana 60 Kingpin and Knuckle Wear
Common · medium severityTypical onset: 100,000-180,000 mi
Symptoms: Clunking or popping from front end over bumps, Excessive play in front wheels when jacked up, Wandering steering or vague on-center feel, Grease leaking from knuckle seals
Fix: Rebuild front axle kingpins, replace bushings, bearings, and seals on both knuckles. Requires specialized tools and press work. 10-14 hours labor per side if doing both.
Estimated cost: $1,200-2,200 for both sides with quality parts
5.9L Gas V8 Piston Ring and Bearing Wear
Common · high severityTypical onset: 120,000-180,000 mi
Symptoms: Excessive oil consumption (1 quart per 500-1,000 miles), Blue smoke on startup or acceleration, Low compression on multiple cylinders, Knocking noise from bottom end, especially when cold or under load
Fix: Full engine rebuild with new pistons, rings, bearings, and gaskets. Often combined with head work if heads are off. 20-30 hours labor for complete rebuild. Some opt for reman short block to save time.
Estimated cost: $3,500-6,000 for full rebuild, $4,000-5,500 for short block swap
Transfer Case (NP241/NP205) Leaks and Chain Wear
Occasional · medium severityTypical onset: 120,000-200,000 mi
Symptoms: Gear oil leaking from front or rear seals, Grinding or rattling noise in 4WD, especially during turns, Difficulty shifting into or out of 4WD, Vibration in 4WD at highway speeds
Fix: Reseal transfer case or replace chain and bearings if worn. NP205 is gear-driven and more durable. NP241 chain-drive needs attention sooner. 6-10 hours labor for removal, rebuild, and reinstall.
Estimated cost: $800-1,600 depending on internal damage
Leaf Spring and Shackle Failure
Common · medium severityTypical onset: 100,000+ mi or sooner if overloaded
Symptoms: Sagging rear end or uneven ride height, Clunking from rear suspension over bumps, Broken or cracked leaf springs visible on inspection, Rusted or seized shackles and bushings
Fix: Replace rear leaf spring pack and shackles. Front springs less common but check if truck was regularly overloaded. 4-6 hours labor for rear springs both sides.
Estimated cost: $600-1,200 for rear spring pack replacement
Steering Box Wear and Leaks
Occasional · medium severityTypical onset: 100,000-160,000 mi
Symptoms: Excessive play in steering wheel (more than 2 inches), Power steering fluid leaking from sector shaft seal, Wandering on highway, requires constant correction, Groaning noise when turning at low speeds
Fix: Rebuild or replace steering box (Saginaw unit). Adjustment may buy time but seal leaks require rebuild. 3-5 hours labor for R&R.
Estimated cost: $400-900 for rebuild or reman box
Buy the Cummins diesel if you can find one with maintenance records—it'll outlast the truck around it. Avoid high-mileage gas V8s unless you're prepared for an engine rebuild, and budget for front-end and transmission work on any W350.
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.