1970 AMC AMX

Symptoms: Pink or milky transmission fluid indicating coolant contamination, Transmission slipping or refusing to shift after overheating, Sudden loss of forward gears following cooling system work

Fix: The factory transmission cooler inside the radiator corrodes through after decades, mixing coolant and ATF. Once contaminated, the automatic requires complete rebuild or replacement. Fix requires new radiator or external cooler, flush all lines, rebuild trans (8-12 hours labor). Prevent by installing external cooler and bypassing factory unit.

Estimated cost: $2,200-3,800

Typical onset: 80,000-120,000 mi

Symptoms: Deep knocking noise on startup that may quiet when warm, Low oil pressure at idle (under 10 psi hot), Metallic rattling under acceleration, Metal flakes or glitter in oil during changes

Fix: AMC V8s are durable but suffer when oil changes were skipped or wrong viscosity used. Bearing wear progresses to spun bearings and crank damage. Requires engine removal, complete disassembly, crank machining or replacement, new bearings, cam inspection, and reassembly (24-32 hours). Many opt for short block replacement instead of rebuild due to parts availability.

Estimated cost: $4,500-7,500

Symptoms: Hard starting when hot, fine when cold, Fuel smell in cabin or garage, Rough idle or stumbling after sitting, Visible fuel weeping at tank seams or sender

Fix: After 50+ years, fuel tanks develop internal rust and external leaks, rubber hoses crack, mechanical fuel pumps weaken, and sediment clogs filters and carbs. Typical fix involves tank removal and cleaning or replacement, all new hoses and filter, fuel pump replacement, and carburetor rebuild (8-14 hours total). Many upgrade to inline electric pump.

Estimated cost: $800-1,600

Typical onset: 70,000-100,000 mi

Symptoms: Clunking when shifting from park to drive or reverse, Excessive driveline vibration at highway speeds, Visible transmission sag when inspected on lift, Shifter feels loose or imprecise

Fix: The rubber transmission mount deteriorates and the crossmember can crack from age and stress, especially with V8 torque. Requires transmission support, mount replacement, and crossmember inspection or welding repair (2-4 hours). OEM-style mounts still available but some aftermarket units fail prematurely.

Estimated cost: $300-650

Typical onset: 90,000-130,000 mi

Symptoms: Blue smoke on startup that clears after warmup, Oil consumption exceeding 1 quart per 500 miles, Low compression on multiple cylinders (under 120 psi), Fouled spark plugs with oil deposits

Fix: AMC V8s develop ring wear from extended oil change intervals or improper break-in after rebuilds. Cylinders glaze over time, preventing rings from sealing. Proper fix requires full teardown, bore and hone, new pistons and rings (20-28 hours). Band-aid approach is ring replacement without boring but rarely lasts (12-16 hours).

Estimated cost: $3,200-5,800

Symptoms: Sudden catastrophic knocking and loss of power, Metal debris throughout engine oil, Visible crack in crankshaft during teardown, Typically occurs without warning after hard acceleration

Fix: The 390 crankshafts had occasional casting porosity issues leading to stress cracks and failure, though rare. Requires complete engine disassembly, crankshaft replacement (often requires machine shop sourcing), and full rebuild (28-36 hours). This is engine-out, full rebuild territory. 290 and 343 cranks are more reliable.

Estimated cost: $5,500-8,500