1985 CHEVROLET C30

Typical onset: 80,000-150,000 mi

Symptoms: Clunking when shifting into gear, Excessive driveline vibration, Visible sagging of transmission tailshaft, Hard shifting or grinding

Fix: Transmission mounts rot out from road salt and oil contamination. Crossmember often cracks at mounting points. Requires transmission support, removal of driveshaft, and replacement of mounts and sometimes the crossmember itself. 2-3 hours labor if straightforward, but rusted hardware can double that.

Estimated cost: $300-700

Typical onset: 150,000-200,000 mi

Symptoms: Severe rod knock at idle, Metal shavings in oil, Loss of oil pressure, Visible oil smoke from breather, Knocking that worsens under load

Fix: These engines were often overloaded and under-maintained in commercial service. Rod bearings wear out first, followed by mains. Requires full short block rebuild or replacement—engine removal, machine work, new pistons/rings/bearings. Figure 20-30 hours for removal, rebuild, and reinstall depending on shop efficiency and parts availability.

Estimated cost: $3,500-6,500

Typical onset: 120,000-180,000 mi

Symptoms: Hard starting when cold, Loss of power under load, Black smoke at acceleration, Fuel in crankcase oil, Engine runs but won't rev past 2000 RPM

Fix: The Stanadyne DB2 injection pump is the Achilles heel of the 6.2L. Fuel contamination, wear, and age kill these pumps. Replacement requires timing adjustment and possibly injector servicing. Pump itself is expensive. 4-6 hours labor for experienced diesel tech.

Estimated cost: $1,800-3,200

Typical onset: 100,000-160,000 mi

Symptoms: Growling or whining from front axle under load, Gear oil leaking from pinion seal or axle tubes, Play in front driveshaft at pinion yoke, Hot differential after driving

Fix: The Dana 60 front diff in 4WD models takes abuse from towing and plowing. Pinion bearings wear and seals leak. Full rebuild includes new bearings, seals, sometimes gears if damaged. Requires axle removal, disassembly, setup with dial indicator for proper backlash. 8-12 hours labor depending on parts needed.

Estimated cost: $1,200-2,800

Symptoms: Engine stumbles or dies after sitting, Rust particles in fuel filter, Fuel smell in cab or under truck, Rough idle that clears after running, Visible corrosion on steel fuel lines

Fix: 40-year-old steel fuel tanks rust from inside out, especially if stored outside or if water got in. Steel lines along frame rails rust through. Requires tank removal, cleaning or replacement, and often replacement of hardlines from tank to pump. Carbureted engines more forgiving than TBI systems. 6-10 hours depending on how much line needs replacing.

Estimated cost: $800-1,800

Typical onset: 60,000+ mi

Symptoms: Gear oil pooling under transfer case, Wet spots on rear output seal area, Shift lever boot contaminated with oil, Low transfer case fluid level

Fix: The NP205 is bulletproof internally but seals leak with age. Output seals, input seal, and shift shaft seals all weep. Rear output seal can be done with transfer case in truck (2 hours), but front seal and shift seals require case removal (6-8 hours). Most owners just top off fluid until it becomes excessive.

Estimated cost: $300-900