Chrysler introduced some unique features for the new models. Regulatory demands, safety concerns, and technological advancements were contributors to these changes.
Lock Inhibitor
The new lock “inhibitor” replaced the 1970 transmission interlock feature, which prevented column locking when in “Park” (automatic transmission) or “Reverse” (manual transmission). The inhibitor ring also prevented accidental locking of the steering column if you tried to remove the key while the car was in motion. This new system resulted in smoother shifting and easier linkage adjustment. It was located directly above the ignition key cylinder. To lock the steering column and remove the key, the ring needed to be rotated clockwise and held in position while the ignition switch was placed in the locked position. Instructions were shown on the ring for one-handed operation.
Have you seen a tinted number 9 in the 10,000-place numeral? If so, expect a high-mileage car. The marking device drags violet colored ink over the last numeric tumbler. (Dodge, Plymouth and the AMC design are registered trademarks of FCA US LLC)
New Door Locks
A market survey revealed that customers preferred a keyless locking system. Plymouth added this feature to the 'Cuda. Either door could be locked from inside or outside without the use of a key by simply depressing the lock plunger and closing the door.
Tamper Deterrent Odometer
'Cudas were built with a tamper deterrent odometer to discourage the practice of “running back the mileage.” A special marking device added a violet stain on the 10,000-wheel when the odometer rotated. These stained numerals normally remained out of view until the odometer registered 90,000 miles.
Cassette Stereo Tape Player
'Cuda had a new cassette stereo tape player with a built-in recording feature. Pre-recorded cassettes could be played through the car’s speakers. Radio programs automatically recorded at the correct volume when the record mode was selected. An optional microphone was available for voice or other sound recordings. The factory assembly line microphone had a straight cord and came with lanyard. Ordering the cassette stereo also required rear speakers on hardtop models. The recording feature is believed to be an industry first, available only on Chrysler-built cars.
Self-adjusting rear drum brakes used a tension spring that activated a ratchet to set the bonded brake shoes closer to the drum to compensate for normal wear. Optional front disc brakes were part of a high level of safety on the new Plymouths. Disc brakes resist fading caused by heat build-up compared to drum brakes. (Dodge, Plymouth and the AMC design are registered trademarks of FCA US LLC)
Braking System
Chrysler Corporation manufactured all master cylinders and approximately one-third of its disc calipers in-house. A more-reliable and lower-cost method of bonding disc brake linings to brake shoes was incorporated. A corporate-designed small-bore master cylinder allowed a large single diaphragm power booster to be used in place of the double diaphragm unit. A new lining material for the primary shoe and heavier ribbed front drums improved fade resistance, reduced roughness, and allowed a greater braking reserve on the drum brake system.
Transmission Changes
The part-throttle kickdown was a standard TorqueFlite feature except with the 440-6 and 426 Hemi. At approximately 10 to 40 mph, a Drive to Second downshift was automatically made when the accelerator pedal was partially depressed. The part-throttle hydraulic system had modifications to the valve body, servo piston spring, and governor for extended 2-3 shift patterns. It also included an added 1-2 shift control valve for smoother upshifts and a limit valve to control part-throttle range. TorqueFlite transmissions were all modified to reduce seal failures by using a new and improved seal that increased endurance. A new breather design also tolerated overfills without leaking.
Shift effort is lower for the 3-speed manual transmission due to two synchronizer changes: lower pointing angles and lower spring loads. Removal of the 1970 slave linkage further reduced shift efforts in low and reverse gears. Several changes were also incorporated into the 4-speed transmission, which reduced shift effort. These changes were:
• Low-gear ratio revised to 2.44:1 from 2.66:1
• Chrysler transmission fluid AQ-ATF-2848A or Dexron is now used (same as automatic transmission)
• Use of solidly bolted floor shifter levers
• Addition of a double-lever interlock provides improved shift feel
• Removal of the slave linkage resulted in easier shifting into reverse
Engine Changes
The engine changes were designed to improve drivability and control oxides of nitrogen (NOx). All engines used the 185-degree F thermostats. This effectively controlled exhaust emissions, particularly at idle.
The 383 4-barrel continued to use an oil windage tray. Compression ratio was reduced from 9.5 to 8.7 to allow operation using regular grade fuels with minimal reduction of power output. This offered the customer a reduced cost per mile. The distributor was recalibrated, and a new intake valve port shape allowed for improved combustion benefiting engine warm-up and drivability.
The 340 4-barrel received a newly designed Carter Thermo-Quad 4-barrel with a plastic main body. The plastic’s low thermal conductivity reduced heat transfer of the fuel. The smaller, triple-primary venturi and larger secondaries result in better performance, improved drivability, and increased fuel economy.
The 426 Hemi engine receive a manual choke.
Torsion Bar
The suspension system was a major difference between 'Cuda and its American-built competitors. Torsion bars are the most efficient way to provide riding comfort and handling. Built-in mechanical adjusters allow the front to be raised or lowered. This resilient steel bar allows the car to maintain excellent ride and handling characteristics as it resists twist. In addition, it helps provide the correct amount of force to hold the wheel to the road.
The Evaporation Control System (ECS) included a vapor-liquid separator mounted in the trunk compartment and connected to the fuel tank as well as vent lines connected to the crankcase breather to reduce fuel vapors from escaping into the atmosphere. This was essentially a closed system to draw fuel vapors into the carburetor for combustion. (Dodge, Plymouth and the AMC design are registered trademarks of FCA US LLC)
Air System
Some modifications were made to the newly named Clean Air System (CAS) for improved vehicle emissions control. In 1970, 'Cudas built in California had an evaporation control system (ECS). All 1971 'Cudas had this installed. The system reduced the loss of fuel from evaporation by drawing vapors from the fuel tank and carburetor into a vent line to the engine air cleaner. It also trapped liquid that escaped from tank due to expansion or overfill. A sealed fuel cap also prevented vapor escape. Inside the fuel tank is a 1.4-gallon thermal expansion tank that allows expansion to occur in a filled tank without forcing liquid fuel out of the system.
The NOx system was mandatory on 'Cuda340 cars registered new in California. The control unit was mounted on the passenger’s side of the firewall in the engine compartment. The white solenoid vacuum valve was located on the rear of the intake manifold. (Dodge, Plymouth and the AMC design are registered trademarks of FCA US LLC)
Nitrogen