1969 BUICK GS

Typical onset: 80,000-120,000 mi original, but many have unknown history

Symptoms: Slipping between gears, especially 1-2 shift, Delayed engagement into Drive or Reverse, Burnt transmission fluid smell, dark or metallic fluid, No movement in any gear

Fix: Full rebuild required in most cases due to worn clutch packs, hardened seals, and valve body issues. Plan on 12-16 hours labor for R&R and rebuild. TH400 is more robust but parts cost more. Consider upgrading to modern internals while you're in there.

Estimated cost: $2,200-3,800

Typical onset: Any mileage on original gaskets, especially after overheating

Symptoms: White smoke from exhaust, sweet smell, Coolant in oil (milky dipstick) or oil in coolant, Overheating with no external leaks, Rough idle, misfiring on one or more cylinders

Fix: Requires removal of intake manifold, exhaust manifolds, accessories, and heads. Machine shop work for resurfacing is typical. Budget 18-24 hours labor plus machine work. Original Buick nailhead-era torque specs and sequences are critical—improper retorque causes repeat failures.

Estimated cost: $3,500-5,200

Typical onset: 100,000+ mi, or unknown service history

Symptoms: Deep knocking sound from bottom end, worse under load, Low oil pressure at idle (below 10 psi hot), Metallic debris in oil or on magnetic drain plug, Sudden catastrophic failure if ignored

Fix: Requires crankshaft removal, inspection, possible grinding, and bearing replacement. If crank needs machining, add 3-5 days lead time. Full engine-out job: 24-32 hours labor. Many shops recommend full rebuild at this point given age and unknowns.

Estimated cost: $4,500-7,000

Typical onset: 90,000+ mi original, or abused engines sooner

Symptoms: Blue smoke on startup or acceleration, Excessive oil consumption (1 qt per 500-800 miles), Low compression readings across multiple cylinders, Poor performance, loss of power

Fix: Requires complete teardown, cylinder honing or boring, new pistons and rings. If bores are worn beyond spec, oversize pistons needed. This is a 30-40 hour job with machine work. Most opt for full rebuild rather than rings alone given labor overlap.

Estimated cost: $5,000-8,500

Typical onset: Any—age and torque are the culprits

Symptoms: Clunking on acceleration or deceleration, Excessive drivetrain movement visible from underneath, Vibration at highway speeds, Transmission tail-housing hitting crossmember in extreme cases

Fix: Mount replacement is straightforward—1.5-2 hours with transmission supported. Check crossmember for stress cracks; welding or replacement adds time. High-torque 400ci cars see this more often. Polyurethane mounts reduce future failures but increase NVH.

Estimated cost: $250-600

Symptoms: Hard starting, stalling after warmup, Fuel starvation under load or at speed, Rust particles in fuel filter, Fuel pump clicking or struggling

Fix: Original steel tanks rust from inside out after decades of ethanol fuel and sitting. Requires tank removal, cleaning or replacement, new sending unit, fuel lines, filter, and pump inspection. Plan on 6-10 hours if doing it all. Many find degraded rubber lines and corroded hardlines once they start digging.

Estimated cost: $800-1,800