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Shop Class: The Past 50 Years of Auto Advances

Half a Century’s Worth of Auto Advances

Alex Steele
Mar 27, 2018
Photographers: ASE Master Technician
From veteran automotive engineers to middle-aged commuters, most have an opinion on the most relevant car and truck advancements over the last 50 years. We’d like to take a trip down memory lane and share some insight from the underside of what we drive.
We’re not going to delve into newly popular high-tech stuff, although we understand the importance of Bluetooth and CarPlay—kidding.
But here are a few remarkable changes and events that stuck with us over time.

Tandem Master Cylinder

The tandem master cylinder was a significant braking upgrade, one that may have saved lives, but it didn’t receive the praise it deserved.
Prior to the mid- to late-1960s, the majority of cars and light-duty trucks came equipped with a single-piston master cylinder attached to the brake pedal.
Photo 2/14   |   Past 50 Years Of Auto Advances Master Cylinder
As we know, hydraulic braking systems work like this: A piston sealed in the bore of the master cylinder pushes hydraulic fluid through lines, hoses, and valves, and then applies force to slave cylinders at each wheel (drum brake wheel cylinders or disc brake calipers). At that point, friction material (drum shoes, disc pads) is applied at the brake drum or disc, respectively, to slow the vehicle to a stop.
The danger of a single-piston master cylinder comes about in the event of any loss of hydraulic pressure. Due to a leaking internal seal of a master piston or a loss of fluid, hydraulic braking at all four wheels is completely lost. The last resort is the “emergency brake,” which mechanically applies the rear brakes using cables attached to a hand or foot lever. And trust us, by no means did this last-ditch effort stop a car safely. At best, a properly functioning emergency brake can achieve less-controlled brake application at the rear wheels, while the majority of braking is needed up front.
Photo 3/14   |   Past 50 Years Of Auto Advances Master Cylinder 2
That’s right, if you blew a brake hose in a dangerous situation and didn’t have the skillset to quickly apply the emergency brake or utilize engine braking by downshifting the transmission, a crash could very well take place.
The tandem master cylinder improved the system considerably. The new design used two pistons, one in front of the other within the master, each applying pressure independently at two wheels instead of all four. So now if you blow a brake hose, there’s still hydraulic pressure applied at two wheels (left front/right rear, or vice versa). This is still not a great way to stop, but it’s a major improvement that can still be used in conjunction with engine braking and the renamed “parking bake” in the event of a hydraulic failure.

Front-Wheel Drive

We were young when front-wheel drive first became popular, so we weren’t fans at all. Losing the muscle-car handling of rear-wheel drive and no longer being able to smoke the tires on a powerslide was not what we wanted.
In truth, front-wheel drive has been around since the beginning of the automobile era and numerous international projects took place (Citroën Traction Avant, Saab 92/93/95/96), but the technology never took hold in U.S. production until the 1980s.
Photo 4/14   |   Past 50 Years Of Auto Advances
The first American-built front-wheel-drive car was the 1929 Cord L-29, but the fullsize coupe some might remember best came out 30 years later with General Motors’ E-body. The ’66 Oldsmobile Toronado shared a platform with the rear-wheel-drive Buick Riviera, but the big Olds (and related Cadillac Eldorado) was one of the first commercially successful front-drive designs in the U.S.
Increasing fuel economy and improved interior space were the forces behind the mass transition to front-wheel-drive compact and midsize American cars. Some say U.S. manufacturers were sparked by production of the Volkswagen Golf and Honda Accord and Civic in the mid-1970s.
The combination of a transverse-mounted engine, transaxle with transmission and differential in one package, constant velocity joint axles, and a unibody chassis reduced weight and saved fuel enough to make the switch a no-brainer.

Engine Mounts

A simple but forgotten mechanical improvement was the restructuring of engine mounts in the early 1970s. Engine mounts are made of rubber, and to this day, they still break and separate over time and miles. Fifty years ago, a broken mount could initiate a dangerous state while driving a lot of cars and trucks.
Photo 5/14   |   Past 50 Years Of Auto Advances Engine Mounts
Hitting the throttle while driving with a broken mount enabled engine torque to actually lift the engine off the frame a half-foot or better. At the time, everybody had a throttle cable connecting the gas pedal to the carburetor. When the engine came off the frame, the length of the cable no longer reached the carb and therefore pulled on the carburetor linkage, sometimes producing an unwanted wide-open throttle situation. Was it dangerous? No doubt. We might consider this an early but founded example of unintended acceleration. (As a witness to the engine-lift problem, we personally—during hard accel—dented a hood from the inside out where the air cleaner made contact.)
Photo 6/14   |   Past 50 Years Of Auto Advances Engine Mounts 2
The fix was modest yet effective. All engine mounts that allow significant engine movement if detached now include steel safety hooks, brackets, or a surrounding structure design to prevent movement beyond an inch or so. It’s not so much a safety feature since electronic throttle control came into production eliminating throttle cables. But now when accelerating with a broken mount you’ll feel and hear a thud as the safety stops do their job, as opposed to engine lift tall enough to bang the hood.


Airbags are everywhere in current automobile production. The National Highway Traffic Administration estimates that 2,756 lives were saved by airbag deployment in 2016—nearly 45,000 between 1987 and 2015—and the number of injuries prevented may be immeasurable.
Photo 7/14   |   Past 50 Years Of Auto Advances Airbags
These statistics prove that supplemental restraint systems (SRS) are a major safety improvement, but it can be difficult to appreciate the advantage airbags provide in a collision without seeing it firsthand.
Vehicles built after front airbags were made standard across the U.S. market (’98 and ’99), driver death rates are 6 percent lower than in model-year ’97 vehicles. It’s might be fair to assume that other vehicle safety systems between the three model years are similar (safety cages, seatbelts, and crumple zones), so airbags may be responsible for the drop in driver death.
Photo 8/14   |   Past 50 Years Of Auto Advances Airbags 2
One 2015 study examined two front-seat occupants riding in the same vehicle during a frontal collision. Both were belted, but only the driver had an airbag. Both the driver and passenger suffered internal injuries, but the passenger suffered spinal damage with temporary partial paralysis. The doctors carrying out the study concluded that airbag use helps provide significant protection against abdominal trauma and injury.

Electronic Stability Control

Here’s what ESC usually means to a technician: customer complaint of the warning indicator on, diagnostic trouble code pertaining to a bad wheel speed sensor, modulator failure, or maybe the need of an ECU software update. The system must be disabled to spin the wheels with a vehicle up on a lift to trace a noise (or do a burnout in the parking lot on a bad day).
A lot of drivers don’t realize how ESC controls throttle and braking to prevent understeer and oversteer and may have never encountered conditions where the system required application.
Photo 9/14   |   Past 50 Years Of Auto Advances ESC
When ESC first came out, before it was as common as a radio, we took part in a manufacturer’s promotional event previewing the system. Typical stuff, but this one really got the point across. Personnel strategically placed cones throughout a large, flat parking lot and thoroughly wetted down the pavement. We were instructed to achieve a speed above 55 mph and weave through the cones driving the subject sedan.
Piece of cake—never lost traction, and the vehicle maintained stability cutting relatively hard turns throughout the run.
Photo 10/14   |   Past 50 Years Of Auto Advances A Trac
The techs on hand then pulled a fuse, the ESC warning indicator cam on, and the system was completely disabled. All were directed to drive the course just like the first time.
Not one driver was able to cut the cones without spinning out (oversteer) unaided by electronic stability control. This was a simple comparative simulation that convincingly taught the advantage of the new system, which has steadily improved since.



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