1973 GMC K2500

Typical onset: 80,000-150,000 mi

Symptoms: Rattling noise from front of engine at cold start that fades as oil pressure builds, Rough idle and difficulty starting when hot, Check timing and find it retarded 8-12 degrees despite static timing being set correctly

Fix: Replace timing chain, gears, and oil pump drive gear. Requires removing radiator, water pump, harmonic balancer, and timing cover. 5-7 hours labor for experienced tech. High-mileage 350/400 SBCs commonly stretch the nylon-toothed cam gear.

Estimated cost: $600-1,200

Typical onset: 60,000-100,000 mi

Symptoms: Clunking or binding when turning in 4WD, Grease leaking from steering knuckles or CV boots, Front differential gear oil dripping from inner axle seals behind knuckle

Fix: Dana 44 front requires disassembly of wheel bearings, spindles, and knuckles to replace inner axle seals and u-joints. Both sides typically need service at once. 6-9 hours labor for full axle rebuild with seal/bearing/u-joint kit. Neglect leads to axle shaft failure and loss of steering control.

Estimated cost: $800-1,600

Symptoms: Gear oil dripping from rear of transfer case onto crossmember, Low transfer case fluid level causing whining in 4WD, Oil spray visible on rear driveshaft yoke

Fix: Remove rear driveshaft, pull output yoke, replace seal and bushing if worn. 1.5-2.5 hours labor. The cast-iron NP205 is bulletproof but seals harden with age. Often accompanied by leaking shift tower gasket.

Estimated cost: $200-400

Symptoms: Black smoke on acceleration, fuel smell in cab, Stumbling or dying when coming off idle, Hard starting after sitting, flooded condition, Fuel dripping from base gasket or air horn

Fix: Rochester Quadrajet needs rebuild kit, float level adjustment, and often new accelerator pump. Ethanol fuel deteriorates internal rubber parts. 3-4 hours for proper rebuild and tuning. Many techs replace with Edelbrock rather than rebuild.

Estimated cost: $350-700

Symptoms: Visible rust perforation on frame rails behind cab, Sagging or cracked body mounts, Rear spring hangers rusted through or separating from frame, Transfer case or transmission crossmember structurally compromised

Fix: Inspect with wire brush before buying. Surface rust is normal; perforation and flaking means frame plating. Crossmember replacement requires drivetrain support, 4-6 hours labor plus welding. Full frame replacement is 20+ hours and rarely economical unless sentimental value.

Estimated cost: $500-3,000

Symptoms: Intermittent stalling or no-start after engine heat soak, Misfiring under load, especially above 3,000 RPM, Difficult cold starting requiring multiple cranking attempts

Fix: Points-type ignition requires adjustment every 10,000 mi. Distributor shaft bushings wear causing timing scatter. Most owners convert to HEI distributor (1-2 hours labor) for reliability. If keeping points, carry spare condenser and coil.

Estimated cost: $150-400

Typical onset: 100,000+ mi

Symptoms: Excessive steering wheel play (more than 2 inches before wheels respond), Wandering at highway speeds requiring constant correction, Clunking through steering wheel on bumps, Gear oil leaking from sector shaft or input shaft seals

Fix: Saginaw manual steering box can be adjusted via sector shaft screw, but worn boxes need rebuild or replacement. 2-3 hours labor to remove, install rebuilt unit. Also inspect pitman arm and tie rod ends simultaneously.

Estimated cost: $400-800