1977 BUICK CENTURY

Typical onset: 80,000-120,000 mi

Symptoms: slipping between gears, especially 1st-2nd, delayed engagement when shifting to Drive, transmission fluid burned smell or dark color, whining noise in gear

Fix: The TH200 (M-29) was GM's weakest automatic and fails predictably. Rebuild runs 8-12 hours labor, but most shops recommend replacement with a junkyard TH350 swap (stronger) which adds 4-6 hours for crossmember and linkage mods. Cooler lines often corroded and need replacement simultaneously.

Estimated cost: $1,800-3,200

Typical onset: 90,000-140,000 mi

Symptoms: excessive oil consumption, 1+ quart per 500 miles, blue smoke on startup and acceleration, low oil pressure at idle when hot, knocking or ticking from crankcase

Fix: The even-fire 231 in '77 still had soft camshaft lobes and undersized main bearings that wore prematurely. Machine work, piston rings, bearings, cam, and gaskets run 18-24 hours. Many owners opt for short block replacement (12-16 hours) or salvage long blocks to avoid core machining costs.

Estimated cost: $2,400-4,500

Symptoms: clunk when shifting from Park to Drive or Reverse, excessive drivetrain movement felt through floorboards, vibration at idle in gear, visible transmission sag when inspected on lift

Fix: Rubber mounts deteriorate badly after 40+ years regardless of mileage. Replacement is straightforward: 1.5-2 hours labor with transmission support. Often done alongside transmission cooler line work since you're already under there.

Estimated cost: $150-300

Symptoms: fuel odor after sitting, especially in hot weather, hard starting when hot, flooding and black smoke, fuel dripping from air cleaner base

Fix: Rochester 2-barrel carbs (V6) and Quadrajet (V8) develop stuck float needles and hardened float materials from ethanol fuel exposure. Rebuild kits run 2-3 hours labor but originals often had pot metal castings that don't respond well to modern fuel. Many techs suggest aftermarket Edelbrock conversions (4-5 hours with tuning).

Estimated cost: $300-800

Symptoms: transmission fluid puddles under front of vehicle, pink or red fluid on radiator or frame rails, low transmission fluid level, overheating transmission

Fix: Steel cooler lines rust through at bends and mounting points, especially in rust-belt cars. Replacement with pre-bent or custom brake line runs 2-3 hours including radiator cooler inspection. Always replace both lines and flush the system to clear debris.

Estimated cost: $250-500

Typical onset: 100,000+ mi

Symptoms: metallic knock that changes with clutch pedal (manual) or hard acceleration, excessive crankshaft endplay measurable with dial indicator, oil pressure fluctuation, eventually progresses to catastrophic failure

Fix: Thrust bearing surface on #3 main wears from clutch abuse or defective bearing design. Requires full teardown, crank measurement, and possibly crank grinding or replacement. If caught early, bearing replacement runs 16-20 hours; if crank is damaged, add machine work or replacement crank costs.

Estimated cost: $2,000-3,800