1965 BUICK GS

Typical onset: 60,000-90,000 mi or after spirited driving

Symptoms: Slipping between gears, especially 1st to 2nd, Delayed engagement when shifting into Drive, Transmission overheating, burnt fluid smell, Hard shifting or complete loss of forward gears

Fix: The ST300 (Super Turbine 300) two-speed wasn't built for the 401's torque in performance use. Requires rebuild or replacement with upgraded clutches and bands. Expect 12-16 hours labor for removal, rebuild, and reinstall. Many owners upgrade to TH400 from later years.

Estimated cost: $2,200-3,800

Typical onset: 80,000-120,000 mi or with neglected oil changes

Symptoms: Heavy knocking from lower engine, especially on cold starts, Rapidly dropping oil pressure at idle, Metallic debris in oil during changes, Sudden catastrophic failure if ignored

Fix: Nailhead bearings suffer from inadequate oiling if maintenance was deferred or wrong oil used. Full teardown required, crank inspection/machining, new bearings, rod bolts, and gaskets. Budget 24-30 hours for proper engine-out rebuild. Many shops recommend full refresh at this point including rings.

Estimated cost: $3,500-5,500

Symptoms: Hard starting when hot, easy when cold, Raw fuel smell, black smoke from exhaust, Poor idle quality, surging at cruise, Gas dripping from carb throat or air cleaner

Fix: The Carter AFB 4-barrel on these cars has aged needle/seat assemblies, cracked floats, and dried-out accelerator pump diaphragms. Most need complete rebuild kits, float adjustment, and proper tuning. Ethanol fuel accelerates deterioration. 3-5 hours for rebuild and tuning on the car.

Estimated cost: $400-750

Typical onset: 70,000-110,000 mi or after overheating

Symptoms: White smoke from exhaust, sweet smell, Coolant loss with no visible leaks, Overheating under load, Milky oil on dipstick or oil cap, Bubbles in radiator when running

Fix: Nailhead heads can warp if overheated even once. Both gaskets typically done together; heads must be checked for flatness and resurfaced. Includes new intake gaskets. 14-18 hours labor assuming no cracked heads.

Estimated cost: $1,800-2,800

Typical onset: all ages, age-related deterioration

Symptoms: Transmission fluid leaking from radiator area or frame rails, Pink fluid puddles under car, Excessive transmission noise or vibration, Clunking when shifting into gear

Fix: Steel cooler lines rust through after 50+ years; rubber mounts collapse from age and heat. Lines need replacement with pre-bent or custom-fabricated units (2-3 hours). Transmission mount replacement adds 1.5-2 hours. Often done together during transmission service.

Estimated cost: $350-650

Symptoms: Sputtering and loss of power under acceleration, Stalling after 15-20 minutes of driving, Engine starving for fuel at highway speeds, Hard starting, long cranking periods

Fix: Original tanks have decades of varnish and rust. Mechanical fuel pump diaphragms harden, inline filters clog rapidly. Replace fuel pump (1.5 hours), install inline filter if missing, and clean or replace tank sending unit. Many need full tank restoration.

Estimated cost: $250-600