Design Notes: 1975 Cadillac Seville
From concept to production reality
Ultimately, the Seville was a car that was made to fit a particular market segment. In an interview from the time-period, GM’s chief designer, Bill Mitchell, stated, “The only other car that was demand-designed, was the first Buick Riviera.” Which, incidentally, had been originally designed for the Cadillac division, as a LaSalle. (1963 Buick Riviera shown to the right.)
As previously discussed, cost considerations had negated any hopes of basing the model on a foreign-sourced GM vehicle. Further, Mr. Mitchell and Mr. Templin, both strong advocates for FWD, acceded to the infeasibility of tooling costs and time constraints associated with making such a unique model a puller rather than a pusher (the only FWD hardware available was reportedly too big for this application and new development costs were astronomical). A concerted effort for independent rear suspension was also snuffed by cost-to-benefit considerations. Rotary power didn’t stand a chance.
In November of 1973, a basic clay model of the yet-to-be-named Cadillac was approved. By the end of December, previously disjointed ideas (relating to the mechanical end of things) were deliberated, and turned into plans. By January 1974, GM had approved those plans. The result would be a vehicle introduction merely 16 months later, two months faster than any prior project had been realized.
To the chagrin of many, the newly established plans called for a RWD sedan based on GM’s X-body platform. The X-body was already in use under the Chevrolet Nova, Pontiac Ventura, Oldsmobile Omega, and Buick Apollo. (1975 Chevrolet Nova shown to the left.)
While the X-body decision swiped the rug out from under many of Cadillac’s aspirations, it likewise freed up a substantial amount of the budget to be reinvested into refining the car. (Cadillac didn’t have much room to complain about the X-body decision, since it was largely dictated by their unrelenting desire for a 1975 model year introduction.)
Earlier I had mentioned the car missed its roughly $8,000 original price target by over 50 percent. Though substantial tooling money was conserved in some areas, those savings were spent in others, and then some. The cost estimates continued to incrementally increase until landing the car at its final price tag of $12,479. That amount positioned the car near the top of Cadillac’s line, only being out-priced by the limited-production Seventy-Five sedan ($14,231) and Seventy-Five limousine ($14,570).
However, because of the substantial money that was reinvested, the car shared little with its lesser X-body brethren.
X-body no more
There wasn’t much of the X-body platform remaining after Cadillac’s engineers had spent time with it. Weighing in at 440 pounds more than the existing X-bodies, the Cadillac was 7.3 inches longer. It rode on a 114.3-inch wheelbase, which was 3.3 inches longer than its relatives, providing additional rear-seat room. Although the front and rear suspension systems remained largely intact, Cadillac’s version naturally had unique tuning in addition to other significant differences. For example, the rear includes an anti-roll bar, and the leaf springs utilized Teflon liners between each spring in order to keep stiffness consistent and constant throughout the life of the part.
Cadillac also included a pneumatic self-leveling system at the rear that can handle a load, up to 800 pounds, without any sagging. The front-end structure, as described by Mr. Templin, was unique to the automotive world in that it utilized a front sub-frame which was attached to the body sheet metal via tiny vertical shock absorbers (which dampened motions between the two major components).
The X-bodies came with 14-inch wheels, whereby Cadillac installed 15 inchers that were six inches wide and fitted with Firestone steel-belted GR78x15B radial tires. For braking, Cadillac made a somewhat cost-influenced decision to go with front discs but rear drums. Mr. Templin’s position on the matter was summed up thusly, “We can do a job that’s 99 percent as good with 11-inch discs in front and 11-inch drums in the rear.” While the other X-bodies used rear drums, Cadillac’s are an inch and a half larger in diameter. An interesting fact is that, while rear discs were considered, no tooling could be found in the GM parts bin that would fit—including from the Corvette. However, Cadillac wasn’t too intent on rear discs because of noise concerns. “We like to stop a car, but we won’t tolerate any grunts, squeals, or shudders,” Mr. Templin stated.
Motivating the car was an Oldsmobile-built, 350-cubic-inch V-8, attached to a Model 375 Turbo Hydra-Matic transmission (which was a variant of the larger-capacity Model 400). The engine produced 180 HP at 4,400 RPM (10 HP more than the Oldsmobile version) and 275 pound-feet of torque at 2,200 RPM. This would propel the car to 60 MPH in ten to eleven seconds and to a top speed of roughly 115 MPH. (An interesting fact about this motor is that it was capable of meeting federal emissions standards—in all 50 states—without a catalytic converter. But, in order to save the costs and time associated with performing 50,000 mile tests to prove it, all of the cars came equipped with one.)
That which was carried over from the X-bodies included the front-door inner panels, door hinge centerlines, the cowl, and basic air conditioning components. So, not much remained and nothing really visible.
In fact, the platform had so much changed from its X-body roots that the X-body designation was finally dropped by Fisher Body’s record keepers and a new one applied. The new designation was K-body. The reason behind the particular letter’s selection was nothing more than it happened to be available.
Although, an interesting side note about the K-body designation is its immediate history. It had previously been assigned to a project of John Delorean’s (while he was still employed at GM). Mr. Delorean’s K-body project was for a low-priced Camaro. That project was aborted. “I got a sort of sinking feeling in my stomach when we were awarded that letter,” Mr. Templin said recalling the former, ill-fated project’s designation.
I hope Mr. Templin didn’t lose too much sleep. Everything worked out fine.