The 1991 Fifth Avenue rides on Chrysler's M-body platform with the A-604 (Ultradrive) 4-speed automatic—one of the most problematic transmissions ever deployed. Engine-wise, these are reasonably durable but suffer classic valve-cover and intake-manifold gasket leaks as they age.
A-604 Ultradrive Transmission Failure
Common · high severityTypical onset: 60,000-120,000 mi
Symptoms: Harsh or delayed shifts, especially 2nd to 3rd gear, Slipping under load or complete loss of forward gears, Transmission overheating, burnt fluid smell, Check engine light with speed sensor or solenoid codes
Fix: Early A-604s had weak governor pressure solenoids, valve body failures, and inadequate cooler capacity. Rebuild requires updated solenoid pack, valve body overhaul, clutch packs, and often external cooler addition. 8-12 labor hours for R&R and rebuild.
Estimated cost: $1,800-3,200
3.3L/3.8L Intake Manifold Gasket Leaks
Common · medium severityTypical onset: 80,000-140,000 mi
Symptoms: Coolant loss with no visible external leaks, White smoke at startup or sweet smell from exhaust, Rough idle, occasional misfire codes, Oil contamination with coolant (milky dipstick)
Fix: The lower intake plenum gaskets deteriorate, allowing coolant into crankcase or cylinders. Requires plenum removal, gasket set, fresh coolant. 4-6 labor hours. Address valve cover gaskets simultaneously—they leak on nearly all survivors.
Estimated cost: $600-1,100
Transmission Oil Cooler Line Corrosion
Common · high severitySymptoms: Transmission fluid dripping from radiator area or frame rails, Low fluid level on dipstick, pink puddles under car, Sudden transmission slipping after fluid loss
Fix: Steel cooler lines rust through where they pass near subframe or enter radiator. This kills the already-fragile transmission fast. Replace both lines, flush cooler, refill with ATF+4. 2-3 hours labor. Do NOT delay—a quart low will destroy the A-604.
Estimated cost: $250-500
Crankshaft Position Sensor Failure
Occasional · high severityTypical onset: 90,000-150,000 mi
Symptoms: No-start condition, cranks but won't fire, Stalling while driving with no restart for 20-30 minutes, Check engine light with crank sensor code
Fix: The Hall-effect crank sensor behind the transmission bellhousing fails from heat. Requires lifting vehicle, access from underneath. 1.5-2 hours labor. Sensor is inexpensive but essential—keep a spare in the glovebox on high-mileage examples.
Estimated cost: $150-300
Front Suspension Ball Joint and Tie Rod Wear
Common · medium severityTypical onset: 70,000-110,000 mi
Symptoms: Clunking over bumps, especially when turning, Wandering or loose steering feel, Uneven tire wear on inside or outside edges, Steering wheel off-center after hitting potholes
Fix: Lower ball joints and outer tie rod ends wear due to weight and soft bushings. Alignment always required after replacement. Plan on 3-4 hours labor for both sides plus alignment. These cars eat ball joints if alignment isn't maintained.
Estimated cost: $500-850
HVAC Blower Motor Resistor and Motor Failure
Occasional · low severitySymptoms: Blower only works on high speed setting, No air flow on any setting, Burning smell from vents, blown fuse
Fix: The resistor block behind the glove box burns out, or the motor itself seizes. Resistor is 20-minute fix, motor requires dash panel removal—1.5 hours. Common enough that parts stores stock them. NHTSA recalled some for motor fire risk.
Estimated cost: $120-350
Buy only if the transmission has been recently rebuilt with updated parts or already replaced—the A-604 will bankrupt you otherwise, and most survivors are on borrowed time.
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.