1970 GMC K2500

Typical onset: 80,000-150,000 mi or after 50+ years regardless of miles

Symptoms: rattling noise from front of engine on cold start that quiets after warmup, erratic ignition timing that won't stay adjusted, rough idle and hesitation, metal shavings in oil, check timing marks—they'll be off several degrees

Fix: Replace timing chain, gears, and tensioner. On small-blocks (307/350) this is a front cover-off job requiring radiator removal, harmonic balancer puller, and new cover gasket. Figure 6-8 hours labor. Big-blocks (396/402/454) similar but more cramped. The 292 I6 is easiest at 4-5 hours. Use double-roller chain kit, not single-row. Often find worn cam gear teeth or cracked nylon teeth on OEM composite gears.

Estimated cost: $600-1,200

Symptoms: hard starting when cold or hot, black smoke and fuel smell—running extremely rich, flooding and gas puddling in intake, high idle that won't come down, flat spots on acceleration, fuel leaking from accelerator pump or bowl gaskets

Fix: These 1970 Rochesters (Quadrajet on V8s, 2-barrel on I6) have 50-year-old gaskets, deteriorated floats, and gummed passages. Professional rebuild with proper kit runs 3-4 hours labor including removal, disassembly, ultrasonic cleaning, and tuning. Alternatively, replace with remanufactured unit (1-2 hours swap time). Ethanol fuel accelerates rubber and cork deterioration.

Estimated cost: $350-750

Symptoms: pedal slowly sinks to floor when holding at stop, fluid leaking from master cylinder pushrod boot, uneven braking side-to-side, rusty brake fluid in reservoir, soft pedal that requires pumping

Fix: Single-chamber master cylinders were still common in 1970—catastrophic failure means total brake loss. Replace with dual-chamber upgrade (strongly recommended). Also inspect all steel brake lines for rust-through, especially along frame rails and rear axle. Budget 2-3 hours for master cylinder alone, add 4-8 hours if replacing rusted hard lines. This is 50-year-old steel—plan on some line replacement.

Estimated cost: $400-1,500

Typical onset: 60,000-100,000 mi

Symptoms: clunking over bumps from front end, steering wander and vague on-center feel, excessive play when grabbing tire at 12 and 6 o'clock, uneven tire wear on inside edges, grease seeping from knuckle caps

Fix: Dana 44 front axles use kingpins instead of ball joints. These wear out bushings and develop slop. Proper job requires knuckle removal, bushing press-out/in, kingpin replacement, and careful reaming for fit. Plan 8-10 hours for both sides with alignment. Many shops won't touch this—it's old-school work. Parts are available but labor-intensive.

Estimated cost: $1,200-2,000

Symptoms: fuel gauge reads empty or erratic regardless of fuel level, fuel smell under truck or in cab, rust flakes in fuel filter, hard starting after sitting—fuel draining back, visible external rust or seepage on tank

Fix: Steel tanks from 1970 rust from inside-out, especially if truck sat with stale fuel. Sending unit gets corroded and binds. Tank replacement requires bed removal or siphoning and dropping—3-4 hours labor. Many shops recommend new tank, sending unit, and pickup screen as a package. Consider adding inline filter before fuel pump.

Estimated cost: $500-900

Symptoms: visible rust perforation on frame rails, sagging or cracked crossmembers, body mount bushings pulling through rusted frame, cracks near spring hangers or shock mounts, visible scaling rust on inner frame channels

Fix: Northern and coastal trucks suffer badly. Critical areas: rear spring hangers, body mounts, and transmission crossmember. Surface rust is cosmetic, but perforation or scaling that flakes off means structural compromise. Repair involves cutting out bad sections and welding in patch panels or replacement sections—highly variable labor from 10-40 hours depending on extent. This is a deal-breaker inspection point.

Estimated cost: $1,500-8,000

Typical onset: Every 10,000-15,000 mi or annually

Symptoms: engine missing and running rough, difficult starting, loss of power under load, visible pitting or burning on point contacts, erratic dwell readings

Fix: These trucks came with points-type ignition—requires regular maintenance. Points wear, gap closes, timing drifts. Replace points, condenser, rotor, and cap as a set every 12-15k miles. Takes 1 hour with dwell meter and timing light. Many owners convert to Pertronix or HEI distributor swap for reliability—one-time 2-3 hour job that eliminates this maintenance.

Estimated cost: $80-150 for points service, $300-500 for electronic conversion