The 1973 Fleetwood with the 472 V8 is a massive, luxurious beast that suffers primarily from age-related deterioration rather than inherent design flaws. The biggest concerns center around the aging THM 400 transmission, worn engine internals from decades of use, and fuel system degradation from ethanol fuels.
THM 400 Transmission Failure
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Slipping between gears, especially 2nd to 3rd, Delayed engagement when shifting to Drive or Reverse, Transmission fluid dark brown or burnt smelling, Harsh downshifts or no downshift at all
Fix: Full rebuild required in most cases — 12-16 hours labor. These transmissions are robust but 50+ years old now. Hardened seals, worn clutch packs, and valve body issues are typical. Cooler lines often corroded and should be replaced during rebuild.
Estimated cost: $2,200-3,800
472 V8 Low Compression / Ring Wear
Common · medium severityTypical onset: 100,000-180,000 mi
Symptoms: Excessive oil consumption (1 qt per 500-800 miles), Blue smoke on startup or acceleration, Hard starting when hot, Loss of power, sluggish acceleration
Fix: Piston ring replacement requires full engine disassembly — 24-32 hours labor. Often discovers worn cylinder walls requiring bore and oversize pistons. Many owners opt for full rebuild at this point given labor overlap. Head gaskets typically replaced simultaneously.
Estimated cost: $4,500-7,500
Fuel System Deterioration
Common · medium severitySymptoms: Hard starting after sitting, Rough idle and stumbling, Fuel smell in garage, Stalling when warm, Visible fuel weeping at carburetor base or lines
Fix: Ethanol fuel destroys original rubber components. Typical fix involves fuel tank cleaning or replacement, all rubber fuel lines replaced with ethanol-compatible hose (4-6 hours), carburetor rebuild (3-4 hours), and new fuel pump. Filter clogs frequently if tank has sediment.
Estimated cost: $800-1,800
Crankshaft Main Bearing Wear
Occasional · high severityTypical onset: 120,000-200,000 mi
Symptoms: Deep knocking sound from bottom of engine, Low oil pressure at idle (under 10 psi), Metal shavings in oil filter, Knock worsens with load
Fix: Requires engine removal and complete teardown — 28-36 hours labor. Crankshaft must be removed, inspected, and often requires machine shop work (turning or welding). Usually discovered during compression-related repairs. Not a DIY job without significant experience.
Estimated cost: $5,000-8,500
Transmission Mount Collapse
Common · low severityTypical onset: original mounts typically failed by now
Symptoms: Clunk when shifting into gear, Excessive vibration at idle in Drive, Transmission tailshaft appears sagging, Driveline vibration at highway speed
Fix: Simple replacement but requires transmission support — 2-3 hours labor. Rubber deteriorates completely after 50 years. Often ignored until transmission work forces the issue. Inspect crossmember for rust damage simultaneously.
Estimated cost: $250-450
Head Gasket Failure (Both Sides)
Occasional · medium severityTypical onset: varies, often heat-cycle related
Symptoms: External coolant leaks at head/block junction, White smoke from exhaust, Coolant in oil (milky dipstick), Overheating with no visible leaks, Rough idle from coolant entering cylinder
Fix: Both sides typically done together — 14-18 hours labor. Heads should be pressure tested and surfaced. Exhaust manifold studs often break during removal on these engines, adding time. Cooling system completely flushed and thermostat replaced during job.
Estimated cost: $2,800-4,200
Buy only if you're committed to a restoration project or have deep maintenance reserves — plan $3,000-5,000 in deferred maintenance on any runner, double that for a neglected example.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.