1979 PONTIAC GRAND PRIX

Typical onset: 80,000-140,000 mi

Symptoms: Slipping on 1-2 or 2-3 shift, especially under throttle, Delayed engagement into Drive or Reverse, Burnt transmission fluid smell, dark/black fluid color, Shuddering or flaring between gears

Fix: Complete rebuild required in most cases, 8-12 hours labor. TH200 (behind 231 V6 and small V8s) is particularly fragile—often needs upgraded clutches and bands. External cooler lines crack and cause fluid loss, accelerating failure. TH350 is stronger but still wears with abuse or poor maintenance.

Estimated cost: $1,800-3,200

Typical onset: 60,000+ mi or sitting for extended periods

Symptoms: Rough idle, stalling at stoplights, Hesitation or stumble on acceleration, Black smoke from exhaust (rich condition), Hard starting when cold, flooding when hot, Leaking fuel from base gasket or accelerator pump

Fix: Rochester Quadrajet needs rebuild kit, secondary air valve adjustment, and often new accelerator pump. If car sat for years, complete disassembly and ultrasonic cleaning required, 3-5 hours. Internal plastic floats can absorb fuel and sink. Choke pull-off diaphragms crack frequently.

Estimated cost: $350-750

Typical onset: 70,000-120,000 mi

Symptoms: Blue smoke on startup or acceleration, Oil level drops 1+ quart between changes, Fouled spark plugs on one or more cylinders, Visible oil pooling in intake manifold

Fix: Pontiac 301 and Chevy 267 small-blocks notorious for worn valve guides and thin piston rings from factory. Valve seals replacement (cylinder heads off, 10-14 hours) helps temporarily, but many need piston rings or full rebuild by 100k. 231 V6 also burns oil through intake manifold gaskets leaking into ports.

Estimated cost: $1,200-2,800

Typical onset: 90,000+ mi

Symptoms: Oil puddle under bellhousing area after sitting overnight, Oil coating transmission bellhousing and starter, Gradual oil loss not traced to valve covers or oil pan

Fix: Two-piece rope-style rear main seal on most engines; transmission must come out for replacement, 6-8 hours labor. Some techs convert to one-piece neoprene seal during repair. Oil pan and transmission mount replacement typically done at same time since access is there.

Estimated cost: $750-1,400

Symptoms: Body sits lower on one side or leans, Doors don't close properly, misalignment after sitting, Clunking over bumps from body shifting on frame, Visible rust perforation at body mount locations or rear frame rails

Fix: G-body notorious for rotted body mounts and rear frame rail corrosion in salt states. Body mounts are 4-6 hours if caught early, but rotted frame rails require welding/replacement (frame-off procedure). Inspect thoroughly before purchase—cosmetic rust hides structural issues.

Estimated cost: $600-1,200 for mounts; $3,000+ for frame work

Typical onset: 100,000-150,000 mi

Symptoms: Rattling noise from front of engine on cold start, Loss of power, poor fuel economy, Engine runs rough, misfires at idle, Check timing and it's retarded despite correct setting

Fix: Original nylon-toothed timing gears and single-row chains wear out. Requires timing cover removal, new double-roller chain set, and cam gear, 5-7 hours. Often find plastic cam gear teeth in oil pan. If caught late, worn cam lobes may also need addressing.

Estimated cost: $650-1,100

Typical onset: 80,000+ mi or from thermal cycles

Symptoms: Loud ticking or exhaust leak sound from engine bay, Smell of exhaust in cabin with heater on, Visible crack in cast-iron manifold, Failed emissions test due to pre-cat leak

Fix: Oldsmobile V8 manifolds crack between ports from heat cycling. Replacement manifolds or aftermarket headers, 3-5 hours per side depending on AC/power steering clearance. Driver side harder due to steering shaft.

Estimated cost: $400-850