The 1999 LHS pairs Chrysler's refined 3.5L V6 with the 42LE/A604 automatic transmission—a platform known for luxurious highway cruising but plagued by transmission fragility and catastrophic engine failures due to porous cylinder walls, particularly in early 3.5L castings.
42LE/A604 Transmission Failure
Common · high severityTypical onset: 80,000-140,000 mi
Symptoms: Harsh 2-3 or 3-4 shifts, slipping under load, Delayed engagement into drive or reverse, Complete loss of forward gears, limp mode activation, Transmission fluid appears dark or burnt
Fix: Rebuild requires 8-12 hours labor; solenoid pack, clutch packs, and torque converter typical culprits. Many shops recommend replacement over rebuild due to repeat failures. External cooler lines and radiator-mounted cooler both prone to leaks causing cross-contamination.
Estimated cost: $2,200-3,800
Porous Cylinder Wall Engine Failure
Occasional · high severityTypical onset: 100,000-150,000 mi
Symptoms: Excessive oil consumption—quart every 500-800 miles, Blue smoke on cold start or acceleration, Coolant loss with no visible leaks, white exhaust smoke, Overheating, coolant in oil or oil in coolant
Fix: Early 3.5L blocks suffer from casting porosity allowing coolant intrusion into cylinders. Repair requires engine rebuild or replacement—22-30 hours labor. Short block swap is most common route; machine work on original block rarely cost-effective.
Estimated cost: $3,500-5,500
Transmission Oil Cooler Line/Radiator Failure
Common · medium severityTypical onset: 70,000-120,000 mi
Symptoms: Pink or strawberry milkshake appearance in transmission fluid, Transmission fluid visible in coolant reservoir, Sudden transmission slipping after radiator leak, Visible fluid leaks at radiator-mounted cooler connections
Fix: Steel cooler lines rust through; radiator internal cooler can rupture allowing coolant-ATF mixing. Replace radiator, flush transmission (4-6 hours), and install external cooler. If mixing occurred, transmission damage likely requires rebuild within 5,000 miles.
Estimated cost: $800-1,400
Water Pump and Timing Belt Failure
Occasional · high severityTypical onset: 90,000-120,000 mi
Symptoms: Coolant leak from front of engine, Squealing or grinding noise from timing cover area, Engine overheating, temperature gauge climbing rapidly, Catastrophic engine damage if belt breaks—interference motor
Fix: 3.5L is interference engine; belt failure causes valve-to-piston contact. Timing belt service every 100k is critical—8-10 hours labor includes water pump, tensioner, idler pulley. Pump bearing failure can destroy new belt prematurely.
Estimated cost: $800-1,200
Intake Manifold Plenum Gasket Leak
Common · low severityTypical onset: 80,000-140,000 mi
Symptoms: Rough idle, especially when cold, P0171/P0174 lean codes, Whistling or hissing from intake area, Loss of power under acceleration
Fix: Upper plenum gasket fails allowing vacuum leaks. Simple repair—3-4 hours labor to remove plenum, replace gasket and intake boots. Critical to check PCV valve and crankcase ventilation system during repair.
Estimated cost: $400-650
Power Window Regulator Failure
Common · low severitySymptoms: Window drops into door suddenly, Grinding or clicking noise when operating window, Window operates slowly or unevenly, Window off-track, glass tilts forward or back
Fix: Plastic regulator mechanisms break—particularly driver and front passenger. Requires door panel removal and regulator replacement—2-2.5 hours per door. Aftermarket parts fail quickly; OEM or quality aftermarket essential.
Estimated cost: $300-500
Front Lower Control Arm Bushing Failure
Occasional · medium severityTypical onset: 90,000-130,000 mi
Symptoms: Clunking over bumps from front suspension, Steering wander, car pulls one direction, Excessive tire wear on inner edges, Steering wheel off-center after hitting bumps
Fix: Rubber bushings deteriorate; pressed-in design makes bushing-only replacement difficult. Most shops replace entire control arms—2.5-3.5 hours both sides including alignment. Worn bushings cause alignment drift and premature tire wear.
Estimated cost: $500-850
Buy only with documented timing belt service and transmission rebuild/replacement; budget $3,000-5,000 for eventual powertrain repairs before 150k miles—great highway cruiser if you can stomach the risk.
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.