1974 GMC C2500

Typical onset: 80,000-150,000 mi

Symptoms: rattling noise on cold start that disappears when warm, rough idle or hesitation, check engine light or backfiring if severely worn, difficulty starting

Fix: Replace timing chain, gears, and tensioner with full kit. On small blocks (307, 350) this is a 4-6 hour job requiring timing cover removal, oil pan drop, and harmonic balancer puller. Big blocks (396, 402, 454) add another 1-2 hours due to access issues.

Estimated cost: $600-1,200

Symptoms: visible holes in cab corners or rocker panels, soft or spongy floor under carpet, daylight visible from underneath, rust bubbling around rear window lower edge

Fix: Squarebody GMCs are notorious for cab corner rot, especially driver's side. Floor pan replacement requires cutting out old metal and welding in patch panels or complete floor pans. Cab corners are bolt-on but require paint and bodywork. DIY-friendly if you can weld; otherwise 8-16 hours shop labor depending on extent.

Estimated cost: $1,200-3,500

Symptoms: fuel gauge reads empty or erratic, fuel smell around tank area, visible rust or pinholes in tank, hard starting after sitting

Fix: Steel tanks rust from inside out, especially if truck sat for years. Sending units fail from ethanol fuel degradation. Tank removal requires dropping spare tire carrier and unbolting from frame (2-3 hours). New tank plus sending unit runs $250-400 in parts, total job 3-5 hours.

Estimated cost: $500-900

Typical onset: 100,000+ mi

Symptoms: excessive play at steering wheel (more than 2 inches), wandering on highway requiring constant correction, clunking when turning lock-to-lock, steering feels loose or vague

Fix: Factory manual steering boxes wear out, developing internal slop. Adjustment helps temporarily but worn sector shaft means replacement. Aftermarket boxes (Redhead, AGR) are common upgrades. Replacement is 2-3 hours including alignment check. Pitman arm puller required.

Estimated cost: $400-800

Symptoms: hard starting especially when warm, stalling at idle or when coming to stop, black smoke or flooding, rough idle and poor fuel economy

Fix: Rochester Quadrajet carbs varnish internally from sitting or ethanol fuel. Full rebuild with kit takes 3-4 hours for experienced tech, includes removing, disassembly, cleaning, and adjustment on bench. Many owners switch to Edelbrock or Holley for reliability. Fuel filter and inline filter replacement mandatory.

Estimated cost: $350-700

Symptoms: soft or spongy brake pedal, pedal slowly sinks to floor, fluid leaking at wheels or under master cylinder, brake warning light on

Fix: Single-reservoir master cylinders leak internally from age. Rear drum wheel cylinders seep and contaminate shoes. Master cylinder replacement is 2 hours including bleeding. All four wheel cylinders plus shoes is 3-4 hours. Always upgrade to dual-reservoir master for safety ($80-120 part).

Estimated cost: $400-900

Typical onset: 30,000-50,000 mi

Symptoms: missing or hesitation under load, hard starting in damp weather, rough idle, loss of power at higher RPM

Fix: Points-type ignition requires regular maintenance every 12,000-15,000 miles. Cap and rotor develop carbon tracking. Full tune-up with points, condenser, cap, rotor, plugs, and wires takes 2 hours. Many owners convert to HEI distributor from later models for reliability (direct bolt-in upgrade).

Estimated cost: $150-400