The 1955 Chevrolet is celebrated today for its revolutionary V8 engine, but in fact, the entire car was an important leap forward for GM’s best-selling car brand.
When the 1955 Chevrolet was introduced to the assembled press at the General Motors Milford Proving Ground on October 12, 1954, it was described (yawn) as “all new,” but in this case, for once, the public relations people weren’t stretching the truth even a little. This car truly was all new. The fact was that Chevrolet’s engineering had grown dated by the early ’50s, and the updates were a welcome change. As hard as this would be to imagine a few years later, Chevrolets before 1955 were not known for their performance or advanced design.
The numerous improvements included a new box-section frame, redesigned front and rear suspension, tubeless tires, and a 12-volt ignition system—a necessary upgrade to support the high-compression 265 CID V8. As we know, it was the exciting new V8 that came to dominate the Chevrolet story for 1955. But actually, there were a number of interesting developments that are worth a closer look.
This view of the undercarriage above shows off the new ladder frame, which used sturdy box-section rails from front to rear. Meanwhile, a set of 14 carefully calibrated rubber body mounts tied the chassis and body together while isolating the passenger compartment from road shocks and noise. But if you look more closely at the illustration, you may notice something unusual: The frame has no crossmembers between the front and rear. Where did they go?
In this new Chevy, the cowl and firewall assembly doubled as the center frame crossmember, as shown above. A heavy-gauge stamping of double-wall steel construction that formed a natural arch, the cowl assembly added rigidity to the frame and to the front of the body structure as well. Chevy engineers called this piece a “plenum” because it also housed an integrated heater and air-conditioning unit, a feature introduced at GM by Pontiac in 1954. The unitized packaging allowed Chevrolet to offer optional air-conditioning at a more realistic price ($565) for a car in the low-priced field. Previous factory A/C systems used a bulky and costly trunk-mounted evaporator unit.
There was no transmission crossmember, either. Instead, the engine and transmission were supported by a tuned rubber mounting system at the front of the block and the sides of the bell housing (above). This allowed the engine to roll on its natural axis of rotation a limited amount rather than transmitting the rough motions into the chassis structure. In this regard it was similar to Chrysler’s Floating Power system of the 1930s. And with the transmission supported at the bell housing and free at the tail housing, its noise and vibration were isolated from the passenger cabin as well. All ’55-’57 Chevrolets used this mounting system in all engine and transmission combinations, six and V8. Convertible models employed a familiar X-member in the frame for added chassis rigidity.
In another major departure from traditional Chevrolet practice, the ’55 chassis abandoned the tried-and-true torque-tube driveline, adopting Hotchkiss drive with an open propeller shaft and Hooke’s joints front and rear. The modernized setup offered improved wheel control and reduced driveline noise. Meanwhile, the rear leaf springs were moved outboard from the frame rails and the shock absorbers were splayed out as far as possible as well. This design, which the Chevy marketing folks branded “Outrigger Suspension,” offered increased roll resistance but without stiffening the spring rates and thus making the ride suffer.
The front suspension was thoroughly overhauled as well, with upper and lower ball joints replacing the previous kingpin setup and the addition of a new recirculating-ball steering gear. Chevy engineers also took the opportunity at this point to dial a sizable amount of anti-dive into the front suspension geometry (above) to improve driver control under deceleration and braking. While seemingly subtle, these details front and rear provided a major improvement in the car’s handling. (And they may help to explain how the ’55-’57 Chevy chassis became a favorite on the short-track stock-car scene for decades.) While the new ’55 Chevy V8 engine was a hot performer, the new chassis was a performer, too. And it didn’t take long for the news to spread that Chevrolet was now in the performance car business.
Article courtesy of Mac's Motor City Garage