1973 PONTIAC FIREBIRD FORMULA

Typical onset: 80,000-120,000 mi

Symptoms: Slipping between gears, especially 1-2 shift, Delayed engagement when shifting into Drive or Reverse, Burnt transmission fluid smell, dark/metallic fluid, Harsh or erratic shifts under throttle

Fix: Full rebuild required in most cases due to worn clutch packs, bands, and seals. Includes R&R transmission (6-8 hours), rebuild internals, replace torque converter if contaminated, new mounts and cooler lines recommended. TH400 is more robust but parts cost more.

Estimated cost: $2,200-3,800

Typical onset: 100,000-150,000 mi

Symptoms: Deep knocking sound from crankcase that increases with RPM, Low oil pressure at idle (under 10 psi hot), Metallic debris in oil filter during changes, Knock worsens when engine is under load

Fix: Requires crankshaft removal, inspection, and likely machining plus new bearings. If crank is scored beyond .030 under, need replacement crank. Labor-intensive: engine pull (8-10 hours), machine work, reassembly. Often triggers full rebuild since you're already that deep. 455 cranks harder to source than 400.

Estimated cost: $3,500-6,500

Typical onset: 90,000-130,000 mi

Symptoms: Blue smoke on startup and deceleration, Excessive crankcase pressure, oil pushing past valve covers, High oil consumption (quart every 500-800 miles), Poor compression test results, uneven across cylinders

Fix: Requires engine teardown, cylinder honing or boring if taper exceeds .005, new pistons if cylinders need oversizing, new rings minimum. Often combined with valve job since heads are off anyway. 16-22 hours total labor for proper ring job including reseal. 1973 low-compression pistons actually held up better than earlier high-comp, but 50 years is 50 years.

Estimated cost: $2,800-4,500

Symptoms: Clunking when shifting from Park to Drive, Excessive drivetrain vibration at idle in gear, Visible transmission sag or misalignment, Driveshaft vibration or u-joint binding from angle change

Fix: Rubber transmission mount deteriorates from age, heat, and fluid leaks. Support transmission with jack (2 hours labor), replace mount and inspect crossmember for cracks or rust-through. Crossmember replacement adds 1-2 hours if compromised. Common on all second-gens due to rubber compound breakdown over decades.

Estimated cost: $250-600

Symptoms: Hard starting after sitting, runs fine once going, Fuel starvation under acceleration or at highway speed, Rust particles visible in fuel filter, Fuel smell in trunk area or visible seepage at sender

Fix: Original steel fuel lines rust from inside out after ethanol fuel exposure. Tank develops internal rust if car sat for years. Requires tank drop (3-4 hours), clean or replace tank, new sender seal, replace all rubber hoses and filter. Steel hard lines often need replacement from frame to pump. Not mileage-dependent—purely age and storage conditions.

Estimated cost: $800-1,800

Typical onset: 100,000+ mi

Symptoms: Rattling noise from timing cover at cold startup, Rough idle and poor performance despite fresh tune, Ignition timing drifts, won't stay set, Metal shavings in valley during valve cover removal

Fix: Original nylon-toothed cam gears and single-row chains wear out. Requires front engine disassembly: radiator, harmonic balancer, timing cover (6-8 hours). Replace with double-roller chain and steel gear set. Critical on 455s which have more crank flex. Check for cam wear while you're in there—flat lobes are common on these low-zinc-era engines.

Estimated cost: $900-1,600