1972 AMC JAVELIN

Typical onset: 90,000-140,000 mi

Symptoms: delayed engagement when shifting into drive, slipping between 2nd and 3rd gear under load, burnt transmission fluid smell, whining or grinding noises in gear

Fix: Full rebuild required in most cases — expect 12-16 hours labor. Clutch packs, bands, and seals are the usual culprits, but these units often have worn pump bushings and valve body issues from sitting. Cooler lines and external cooler replacement recommended during rebuild.

Estimated cost: $2,200-3,800

Typical onset: 80,000-120,000 mi

Symptoms: blue smoke on startup and acceleration, burning through a quart every 500-800 miles, fouled spark plugs, low compression readings on multiple cylinders

Fix: Ring replacement requires full engine teardown — 20-28 hours labor depending on V8 size. Often discover worn cylinder walls requiring a bore and hone. If main bearings show wear, budget for a full rebuild. The 401ci is particularly prone to ring land damage from detonation.

Estimated cost: $3,500-6,500

Symptoms: excessive driveline clunk when shifting from park to drive, vibration at idle that smooths out at speed, visible engine movement when revving, transmission crossmember sagging or cracked

Fix: All mounts use 50-year-old rubber that's usually collapsed or torn. Transmission mount replacement is 1.5-2 hours, engine mounts add another 2-3 hours. Often find the crossmember itself needs reinforcement welding. Do them all at once.

Estimated cost: $400-750

Symptoms: hard starting when hot, stumbling and hesitation during acceleration, fuel smell in cabin, rough idle that doesn't respond to tuning, fuel leaks at rubber line connections

Fix: Carter/Motorcraft carbs gum up badly if the car sat. Full rebuild kit plus ultrasonic cleaning is 4-6 hours. Replace all rubber fuel lines — originals are rock-hard. Add mechanical fuel pump rebuild or replacement (common diaphragm failure). Inline filter on these is often overlooked and plugged solid.

Estimated cost: $600-1,200

Typical onset: 100,000-150,000 mi

Symptoms: heavy knocking from bottom end that worsens under load, excessive crankshaft endplay, metal shavings in oil and filter, oil pressure drops significantly when warm

Fix: Requires complete engine removal and teardown — 24-32 hours labor minimum. Often need crankshaft grinding and oversized bearings. If thrust bearing failed completely, expect crank replacement. The 304 and 360 share bottom-end parts, but 401 cranks are getting scarce and expensive.

Estimated cost: $4,500-7,500

Symptoms: transmission fluid in radiator or coolant in transmission, corroded steel cooler lines leaking at fittings, transmission overheating on highway drives, pink milky substance on dipstick

Fix: Factory cooler inside radiator can leak internally, contaminating both systems. Requires radiator replacement or external cooler bypass (2-3 hours), plus full transmission fluid flush and filter change. Steel lines rust through at frame contact points — replace with pre-bent or custom flare new ones (add 2-4 hours).

Estimated cost: $800-1,600

Symptoms: coolant consumption without external leaks, white smoke from exhaust, overheating under load, misfires on specific cylinders, hydrocarbon contamination in coolant

Fix: The 401 heads crack between valve seats or into water jackets, especially if overheated. Head removal and inspection is 14-18 hours, plus machine work or replacement heads (getting expensive). Often discover warpage requiring milling. Budget for full gasket set and ARP studs while you're in there.

Estimated cost: $3,200-5,500