1979 CHEVROLET C20

Typical onset: 120,000-180,000 mi

Symptoms: Harsh or delayed 1-2 shift, especially when cold, Slipping under load in 2nd or 3rd gear, Burnt transmission fluid smell or dark/gritty fluid, Whining or grinding noise from bellhousing area

Fix: Full TH400 rebuild with hard parts inspection, new clutches, bands, seals, and filter. Expect 12-16 hours labor for removal, rebuild, and reinstallation. Transmission cooler lines and radiator cooler should be flushed or replaced simultaneously.

Estimated cost: $1,800-3,200

Typical onset: 150,000-200,000 mi

Symptoms: Oil pressure drops below 10 psi at hot idle, Knocking or ticking from lower engine block under load, Metal shavings in oil filter or on magnetic drain plug, Pressure warning light flickering at stoplights

Fix: Requires crankshaft removal, bearing inspection, possible crank turning or replacement, and full lower-end rebuild. Small-block 350 takes 18-24 hours, big-block 454 adds 4-6 hours. Often cheaper to swap in rebuilt short block if cylinder walls are also worn.

Estimated cost: $2,500-5,000

Symptoms: Hard starting when hot, floods easily, Rough idle or stalling at stop signs, Black smoke from exhaust, fuel smell in cab, Poor fuel economy, worse than the already-bad 8-10 mpg baseline

Fix: Quadrajet rebuild kit with new needle/seat, float adjustment, accelerator pump, and choke calibration. Carburetor removal and bench rebuild takes 3-5 hours for a technician familiar with Quadrajets. Many shops now recommend Edelbrock or Holley swap instead for reliability.

Estimated cost: $350-700

Typical onset: 140,000-200,000 mi

Symptoms: Blue smoke on startup or deceleration, Consuming 1+ quart of oil per 500-800 miles, Loss of compression across multiple cylinders, Fouled spark plugs, especially on I6 292

Fix: Full ring job requires head removal, cylinder honing, new rings and gaskets. If cylinders are out-of-round beyond spec, requires overbore and oversized pistons. Labor is 16-22 hours for V8s, 12-16 for inline-six. If cylinder walls are scored, short block replacement is more cost-effective.

Estimated cost: $1,600-3,500

Symptoms: Visible rust perforation on frame rails behind cab, Transmission crossmember cracking or sagging, Body mounts disintegrating, causing cab misalignment, Fuel or brake line mounting points corroded away

Fix: Frame repair involves cutting out bad sections and welding in new steel plate or boxed tubing — 8-16 hours depending on extent. Crossmember replacement is 4-6 hours including transmission support. Severe cases may require full frame-off restoration or chassis swap, which is rarely economical unless truck has sentimental value.

Estimated cost: $1,200-4,000

Symptoms: Fuel gauge stuck on empty or full, erratic reading, Fuel smell under truck bed, visible rust stains on tank, Running out of fuel despite gauge showing 1/4 tank, Rust flakes in fuel filter, clogging consistently

Fix: Replace fuel tank, sending unit, straps, and all rubber hoses. Tank removal is 3-4 hours, new tank plus sender runs $250-450. If in-tank sock filter disintegrated, also flush fuel lines and replace inline filter. Surface rust on exterior tank isn't critical, but internal rust contamination requires replacement.

Estimated cost: $400-800