1973 BUICK APOLLO

Typical onset: 80,000-150,000 mi or 40+ years of age

Symptoms: Clunking on acceleration or deceleration, Excessive drivetrain movement visible when revving, Vibration at idle that wasn't there before, Transmission feels like it's shifting hard or banging into gear

Fix: Rubber deteriorates with age regardless of mileage. Transmission mount is most common failure point on these X-bodies. Engine mounts crack and separate. Replace all mounts as a set while you're in there. 2-3 hours labor for both transmission and engine mounts.

Estimated cost: $300-600

Typical onset: 100,000-140,000 mi

Symptoms: Slipping between gears, especially 1-2 shift, Delayed engagement when shifting into Drive or Reverse, Burning transmission fluid smell, Harsh or erratic shifts, Fluid dark brown or black despite regular changes

Fix: The TH350 behind the 350 V8 is generally bulletproof but at 50 years old, seals harden and clutches wear. Full rebuild with torque converter runs 12-16 hours labor. Most survivors need this by now if not already done. The 250 I6 uses a lighter-duty transmission that fails earlier.

Estimated cost: $1,800-3,200

Symptoms: Hard starting when engine is hot, Stalling in traffic or after short stops on hot days, Stumbling or hesitation under acceleration, Engine dies and won't restart until it cools 20-30 minutes

Fix: Original metal fuel lines rust from inside out; rubber hoses turn to spaghetti after 50 years. Combination of degraded fuel filter, corroded pickup sock in tank, and heat-soaked fuel causes vapor lock. Replace all fuel lines, filter, and consider electric pusher pump. Routing fuel lines away from exhaust helps. 4-6 hours for comprehensive fuel system refresh.

Estimated cost: $400-800

Typical onset: 120,000-180,000 mi

Symptoms: Blue smoke on startup that clears after warmup, Blue smoke during deceleration, Oil consumption 1 quart per 500-800 miles, Fouled spark plugs, Loss of compression and power

Fix: The 250 I6 and 350 V8 are long-lived but ring wear is inevitable. Compression test reveals the truth. Ring job requires head removal, cylinder honing, new rings and bearings—count on 16-20 hours. If cylinders are scored or tapered beyond spec, you're into a full rebuild or replacement. Many survivors at this age need this work.

Estimated cost: $2,200-3,800

Typical onset: 150,000+ mi or history of low-oil operation

Symptoms: Deep knocking sound from bottom end of engine, Knock increases with RPM and load, Low oil pressure at idle when warm, Metallic debris in oil or filter, Knock that doesn't go away when warm

Fix: Main bearing failure means engine-out, complete teardown. If crank journals are scored beyond turning, you need a crankshaft—rare and expensive for the 250 I6. Complete bottom-end rebuild runs 20-28 hours labor. At this point, sourcing a good used engine or remanufactured long block often makes more financial sense than rebuilding.

Estimated cost: $3,500-6,000

Symptoms: Transmission fluid spots under front of vehicle, Low transmission fluid level, Visible fluid weeping at radiator connections or along steel lines, Transmission overheating if cooler fails internally

Fix: Steel cooler lines rust through where they pass near frame or attach to radiator. Rubber sections at connections crack. Occasionally the cooler inside the radiator fails, mixing coolant and ATF—that requires radiator replacement too. External line replacement is 1-2 hours. Internal cooler failure adds radiator cost and complete fluid flush of both systems.

Estimated cost: $250-900