The 1973 Centurion is Buick's full-size luxury flagship riding the big B-body platform with either the 350 or 455 V8. These are solid cruisers when maintained, but transmission longevity and engine oil consumption become significant issues past 80,000 miles, especially with the 455.
TH400 Transmission Overheating and Cooler Failure
Common · high severityTypical onset: 70,000-120,000 mi
Symptoms: Burnt transmission fluid smell, Delayed or harsh shifts when hot, Slipping in 2nd or 3rd gear after highway driving, Pink milky fluid if cooler leaks into radiator
Fix: The factory transmission oil cooler in the radiator tank fails or the external lines corrode through. If coolant mixes with ATF, you're looking at a full rebuild. Prevention means adding an external cooler and replacing the in-radiator unit. Rebuild takes 8-12 hours including R&R and valve body work.
Estimated cost: $1,800-3,200
455 V8 Excessive Oil Consumption and Ring Failure
Common · medium severityTypical onset: 80,000-150,000 mi
Symptoms: Blue smoke on acceleration or deceleration, Burning through a quart every 500-800 miles, Fouled spark plugs on cylinders 2, 4, 6, 8, Low compression readings below 120 psi
Fix: The 455's soft piston rings wear quickly, especially if overheated even once. Proper fix is a ring job (12-16 hours) or full rebuild if cylinder walls are scored. Many shade-tree guys try high-mileage oil and keep topping off, but that's just delaying the inevitable.
Estimated cost: $2,200-4,800
Crankshaft Main Bearing Wear and Knock
Occasional · high severityTypical onset: 100,000-180,000 mi
Symptoms: Deep knocking sound at idle that quiets with RPM, Low oil pressure below 10 psi hot at idle, Metallic debris in oil filter, Vibration through whole chassis
Fix: Both the 350 and 455 can develop main bearing wear if oil changes were neglected or if the engine ran hot. Requires pulling the crank, checking journals for out-of-round, and installing oversize bearings. Full job is 16-20 hours because you're essentially doing a short block rebuild.
Estimated cost: $3,500-5,500
Transmission Mount Collapse
Common · low severityTypical onset: 60,000-100,000 mi
Symptoms: Clunk when shifting from Park to Drive or Reverse, Excessive vibration at idle in gear, Visible sagging of transmission tailshaft, Driveline shudder on acceleration
Fix: The rubber crossmember mount deteriorates from heat and age. It's a 1.5-2 hour job with the car on a lift—drop the crossmember, swap the mount, reinstall. Dead simple but often ignored until it tears completely.
Estimated cost: $180-350
Fuel System Varnish and Filter Clogging
Occasional · medium severitySymptoms: Hard starting when hot, Sputtering or stalling under load after sitting, Fuel pump working but weak delivery, Engine dies after 15-20 minutes of driving
Fix: Old gas turns to varnish in the tank and lines, especially if the car sat for years. Filter clogs quickly even after tank cleaning. You'll need to drop and clean or replace the tank, blow out all lines, replace filter and pump sock. Budget 4-6 hours if the tank comes out.
Estimated cost: $400-900
Carburetor Rochester 4-Barrel Flooding and Leaking
Occasional · medium severitySymptoms: Raw gas smell in engine bay, Black smoke and rough idle, Gas dripping from carb base or accelerator pump, Hard starting with repeated cranking needed
Fix: The Rochester Quadrajet carbs use rubber-tipped needle valves that harden with age and no longer seal. Float levels go out of spec. A proper rebuild with new kit and float adjustment takes 3-4 hours if you know these carbs; double that if you don't. Many shops now just swap in a reman unit.
Estimated cost: $350-750
Buy a clean 350-powered example with service records and budget $2,000 for deferred maintenance—avoid high-mileage 455s unless the engine's already rebuilt.
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.