1981 PONTIAC SUNBIRD

Typical onset: 120,000-180,000 mi

Symptoms: Heavy knocking from lower engine block, Metal shavings in oil, Sudden loss of oil pressure, Catastrophic seizure if ignored

Fix: The Iron Duke's Achilles heel is crankshaft and main bearing failure, often from oil starvation or wear. Requires full engine teardown, machine work on the crank, new bearings, and typically new rings while you're in there. 18-24 labor hours for in-chassis rebuild, or 12-16 for engine pull and short block swap if machine work isn't viable.

Estimated cost: $2,800-5,200

Typical onset: 60,000-100,000 mi

Symptoms: Excessive driveline clunk on acceleration or deceleration, Vibration through shifter or floor, Transmission appears to 'sag' visually, Difficulty engaging gears (manual)

Fix: The rubber transmission mounts deteriorate badly over time, especially on cars that sat. Simple replacement job but requires supporting the transmission from below. 1.5-2.5 labor hours depending on manual or automatic configuration.

Estimated cost: $180-350

Symptoms: Hard starting when cold or hot, Rough idle and stalling at stops, Black smoke from exhaust (rich running), Poor fuel economy below 20 mpg

Fix: The Rochester 2SE two-barrel carb uses a troublesome electric choke and computer-controlled mixture control solenoid that fail or stick. Ethanol fuel degrades internal gaskets and circuits. Professional rebuild with kit runs 3-4 hours; many techs now swap to Weber or Holley aftermarket carbs (2-3 hours).

Estimated cost: $320-650

Typical onset: 90,000-140,000 mi

Symptoms: Slipping between gears, especially 1-2 shift, No reverse or delayed engagement, Burnt transmission fluid smell, Whining or grinding noises

Fix: The three-speed TH-125C transaxle tends to fail from worn clutch packs and valve body issues. Full rebuild with torque converter runs 12-16 labor hours. These transaxles are getting harder to source; some shops won't touch them due to parts availability.

Estimated cost: $1,800-3,200

Symptoms: Fuel leaks underneath vehicle, Fuel smell in cabin or garage, Difficulty filling tank (vent issues), Engine stumbling from fuel starvation

Fix: After 40+ years, steel fuel tanks rust through and hard fuel lines corrode at connections. Tank replacement requires dropping the rear suspension crossmember (6-8 hours), lines add another 2-4 hours. Many shops recommend doing both simultaneously on high-mileage examples.

Estimated cost: $800-1,600

Typical onset: 100,000-150,000 mi

Symptoms: Blue smoke on startup or acceleration, Consuming one quart of oil per 500-800 miles, Fouled spark plugs, Loss of compression

Fix: The Iron Duke burns oil as rings wear and cylinder walls glaze. Ring replacement requires engine disassembly, honing cylinders, and new rings on all four pistons. Often done during a refresh when crank work isn't needed yet. 14-18 labor hours in-chassis.

Estimated cost: $1,800-3,000