The 1978 AMC Concord is a rebadged Hornet built on AMC's aging but durable platform. The inline-six engines are nearly bulletproof, but transmission cooling issues and rear main seal leaks plague higher-mileage examples, plus typical 1970s carburetor and electrical gremlins.
Torque-Command (TorqueFlite) Transmission Overheating and Failure
Common · high severityTypical onset: 80,000-120,000 mi
Symptoms: Burnt transmission fluid smell and darkened fluid, Slipping between gears, especially 2nd to 3rd, Delayed engagement when shifting into drive, Complete loss of forward gears if cooler lines fail
Fix: Factory transmission oil cooler (inside radiator) is undersized and prone to clogging or internal leaks that cross-contaminate coolant and ATF. Best fix is external aftermarket cooler plus fresh fluid and filter. If already damaged, expect transmission rebuild. Labor: 8-12 hours for cooler install plus rebuild if needed.
Estimated cost: $800-2,800
Rear Main Seal and Oil Pan Gasket Leaks
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: Oil dripping from bellhousing area onto ground, Oil accumulation on transmission case, Low oil level requiring frequent top-offs (quart per 500-800 miles)
Fix: The rope-style rear main seal hardens with age and the one-piece oil pan gasket fails. Rear main requires transmission removal; oil pan needs engine lifted slightly. Smart shops do both simultaneously. Labor: 6-9 hours combined.
Estimated cost: $650-1,200
Carter BBD Carburetor Float and Accelerator Pump Failures
Common · low severitySymptoms: Hard starting when hot (heat soak boils fuel), Hesitation or flat spot on acceleration, Flooding and raw fuel smell in engine bay, Black smoke from tailpipe during warmup
Fix: Ethanol fuel destroys original cork/rubber float and pump diaphragm. Rebuild kit with ethanol-compatible parts runs $40-60. Many owners swap to Weber 32/36 carb for reliability. Rebuild labor: 2-3 hours including adjustment.
Estimated cost: $180-400
Transmission Mount Collapse
Occasional · medium severityTypical onset: 60,000-90,000 mi
Symptoms: Clunk when shifting from park to drive or reverse, Vibration at idle in gear, Visible sag of transmission tailshaft
Fix: Rubber mount deteriorates and transmission drops, stressing driveshaft and shifter linkage. Straightforward replacement but requires supporting transmission. Labor: 1.5-2 hours.
Estimated cost: $120-220
Fusible Link Failures and Charging System Issues
Occasional · high severitySymptoms: Complete electrical failure (no lights, no crank), Ammeter pegged to discharge, Smoke from under-hood wiring near starter relay, Intermittent starting or accessories dying while driving
Fix: AMC used fusible links instead of maxi-fuses; these corrode at connections or fail outright. Alternator diode failures can also overload the system. Requires tracing circuits and replacing links (or upgrading to blade fuses). Labor: 2-4 hours depending on extent.
Estimated cost: $150-450
Valve Cover and Intake Manifold Gasket Oil Leaks
Common · low severityTypical onset: 50,000+ mi
Symptoms: Oil weeping down sides of engine block, Burning oil smell after highway driving, Crusty oil residue on valve cover perimeter
Fix: Cork valve cover gaskets shrink and intake manifold end seals leak over time on the I6 engines. Not hard to fix but requires careful torque sequence on intake (overtightening cracks manifold). Labor: 2-3 hours for both gaskets.
Estimated cost: $200-380
Buy one if you're handy and patient—the drivetrain is stout, but expect to wrench on seals, carbs, and cooling systems regularly at this age.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.