The 1968 Star Chief represents the last year of Pontiac's full-size flagship before the Bonneville took over. Built on the B-body platform with robust 389 or 421 V8s, these cars are mechanically simpler than later emissions-era models but suffer from age-related drivetrain wear, cooling system failures, and carburetor issues typical of 50+ year-old vehicles.
Main and Rod Bearing Wear Leading to Engine Rebuild
Common · high severityTypical onset: 80,000-150,000 mi
Symptoms: Deep knocking noise from bottom end, especially when cold or under load, Oil pressure drops below 10 psi at idle when warm, Metallic debris in oil filter or pan during changes, Gradual loss of compression across multiple cylinders
Fix: Complete teardown required. Machine work on crank journals, line boring, new bearings, rings, timing set. Expect 35-45 labor hours for full rebuild with block removal. Many shops recommend going straight to shortblock replacement if crank needs extensive machining.
Estimated cost: $4,500-7,500
TH400 Automatic Transmission Rebuilds
Common · high severityTypical onset: 70,000-120,000 mi
Symptoms: Harsh 1-2 shift or slipping between gears under throttle, Delayed engagement into Drive or Reverse (more than 2 seconds), Transmission fluid dark brown or burnt smell, Whining noise in Park or Neutral that changes with engine RPM
Fix: TH400 is a strong transmission but clutch packs wear and modulator diaphragms fail. Rebuild involves R&R (8-10 hours), complete disassembly, new clutches, seals, bands, filter, and torque converter inspection. Many units have never been rebuilt and still have original internals.
Estimated cost: $2,200-3,800
Carburetor Fuel Delivery and Tuning Issues
Common · medium severitySymptoms: Hard starting when hot, engine floods easily, Rough idle that changes with engine temperature, Hesitation or stumble during acceleration from stop, Fuel leaking from accelerator pump area or gasket seepage
Fix: Rochester Quadrajet carbs need full rebuild kits after sitting or with old ethanol-degraded fuel. Includes all gaskets, needle/seat, accelerator pump, power piston. Figure 4-6 hours for proper disassembly, cleaning, and tuning. Some shops opt for replacement with remanufactured unit.
Estimated cost: $450-950
Cooling System Failures and Overheating
Common · high severitySymptoms: Temperature climbs into red zone in traffic or climbing hills, Coolant leaking from water pump weep hole or lower radiator hose, Green/orange residue around thermostat housing, Steam from under hood after shutdown
Fix: Original radiators are often clogged or have internal corrosion after 55+ years. Water pumps leak at the impeller seal. Complete cooling refresh includes radiator recore or replacement, water pump, thermostat, hoses, and flush. 6-8 hours for full system overhaul.
Estimated cost: $800-1,600
Worn Frame and Transmission Mounts
Occasional · medium severityTypical onset: 60,000-100,000 mi
Symptoms: Clunking from under vehicle during acceleration or braking, Excessive vibration at idle that diminishes at speed, Visible sag or misalignment of transmission crossmember, Driveline shudder during 1-2 upshift
Fix: Rubber deteriorates even on low-mileage garage queens. Transmission mount replacement requires supporting trans with jack, 2-3 hours. Engine mounts need frame access and can be challenging with accessories in the way. 4-5 hours for all mounts.
Estimated cost: $350-700
Power Steering Pump and Gearbox Leaks
Occasional · medium severitySymptoms: Whining noise during parking lot maneuvers, Power steering fluid puddles under left front or center of vehicle, Steering effort increases noticeably, especially when cold, Low fluid level despite no visible external leaks (internal gearbox wear)
Fix: Saginaw power steering pumps leak at shaft seal or rear housing. Gearbox seals weep at sector shaft. Pump rebuild 3-4 hours, gearbox reseal or replacement 5-7 hours with alignment. Many opt for remanufactured units given age.
Estimated cost: $450-1,200
Buy one if you're comfortable with carburetors and have a budget for eventual engine/trans work, but avoid high-mileage examples unless already rebuilt — these are due for major mechanical refreshes at this age.
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.