3. Clutch/Brake Pedal/Linkage Assembly
3.1. Mechanical Linkage
Unfortunately, the easiest mechanical linkage parts to bolt in can only be found in 1978-1981 GM A body cars. A picture of the pedals and linkages can be found in Figure 3-1. A generic exploded view of the complete assembly can be found in Figure 3-2 (note the frame bracket is not accurately drawn in the exploded view because the picture applies to 1976-1981 A body cars). Part numbers can be found in Section 21. My research has revealed that reproduction parts can now be purchased from The El Camino Store, El Camino Parts, Original Parts Group, or Muscle Cars Only though some parts may need to be further machined by the purchaser. For example, some reproduction frame brackets have no holes to mount it to the frame. These frame brackets are advertised as needing to be welded on. No welding is necessary. I have made a template (available in Section 3.1.4.) to drill the correct holes. When buying reproduction parts, note that each vendor's "complete kit" is not necessarily as complete as one from another vendor. Some kits do not include the clutch pedal stop and bumper. Some kits do not include the correct longer bolt on which the pedals swing, which must be replaced with a longer bolt (7⁄16-14 × 4˝) in order to hang the clutch pedal.
Drawing courtesy of General Motors
The clutch and brake pedal bracket is the same for automatic and manual transmission cars. Although it is not necessary to remove the clutch and brake pedal bracket to remove and replace the pedals, it is easier to remove and replace the unit as an assembly. The neutral safety switch and clutch pedal bump stop are easier to install with the pedal bracket out of the car. It is not necessary to remove the steering column to remove the pedal bracket, but since the steering column should be replaced with a manual transmission type steering column, the steering column may as well come out now.
If a manual transmission brake pedal is not available, one can be made from a large automatic transmission brake pedal. (Note that the large automatic transmission brake pedal was only used with power brakes.) Since the clutch and brake pedal use the same pedal cover, the clutch pedal can be used as a template for trimming the larger brake pedal (Figure 3-3).
The brake pedal installed in 1978-1981 GM A body cars equipped with an automatic transmission and manual brakes is the same pedal installed in cars equipped with a manual transmission. I have only ever seen one of these cars and took the brake pedal (Figure 3-4). Note that the pin for the master cylinder pushrod is a different diameter for power brakes than it is for manual brakes. The pin is also in a different hole. The pin for manual brakes is larger and uses the upper hole. The pin for power brakes is smaller and uses the lower hole. The master cylinder pushrod should fit snugly over the pin. If not, the pin should be replaced with the correct pin for the application.
I have used new pedal covers from Chevrolet and from the MOTORMITE® Pedal-Up™ rack. The Pedal-Up™ covers are softer and grip wet shoes quite well; however, they wore through to the pedal after less than 20 k miles. The Chevrolet covers are much harder, hence, they do not grip wet shoes very well, but they last many times longer than the Pedal-Up™ covers.
The pedal covers are not unique to the A body. The front-wheel drive X body cars use the same pedal covers.
3.1.2. Upper Pushrod
The upper pushrod utilizes the same hole in the firewall as the cruise control harness (1978-1981 A body cars were not available with cruise control combined with a manual transmission). If the car does not have cruise control, the hole will not exist. A dimple below the power brake booster marks the location of the upper pushrod hole. Both of my cars have cruise control and I wanted to retain it, so the harness had to be rerouted.
I found that the best time to install the upper pushrod boot is while the steering column is removed. The boot can be installed while you are under the dashboard by reaching through the firewall where the steering column once was. If you choose not to remove the steering column, the power brake booster must be removed so the boot can be installed from the engine compartment. There are two dimples on the firewall marking the location of the screws to mount the upper pushrod boot.
The upper pushrod and the clutch pedal do not wear well. The pins on the end of the upper pushrod are slowly cut off, and the circular hole in the clutch pedal becomes an oval (Figure 3-5). In 1989, the clutch pedal and upper pushrod were available from GM and I bought replacements, but they have since worn a great deal. (I should have bought more.) As the parts are rare, I developed a prototype replacement upper pushrod (Figure 3-6) using spherical rod ends, though I have not installed it. I built a steel jig (Figure 3-7) using a stock upper pushrod as a model. I then cut the ends off of a stock pushrod and installed spherical rod ends. The next prototype I would have made would have utilized tubing, however, shortly after the initial release of this document, Speed Direct began selling spherical rod end pushrods for the 1978-1981 GM A body (Figure 3-8).
Photograph courtesy of Bob Morris
Most of the bellcranks that I have seen have been broken. The bottom lever on the bellcrank typically peels away from the shaft. The peel-away effect happened to me while driving my 1979 Malibu Wagon. Luckily, I was only about 2 miles from home and was able to upshift and downshift without the clutch. More problems arose when approaching a traffic light and it remained red, so I had to stop. The only way to start moving was to shut the engine off, put the transmission in first gear, and start the engine.
To remedy the peel-away effect, I built a jig (Figure 3-9) from a known good bellcrank. With the bellcrank mounted in the jig, the welds can be repaired or a lever can be replaced. After the repair, reinforcements should be welded onto the tension side of the levers to prevent the lever from peeling away from the shaft (Figure 3-10).
The frames on cars not factory equipped with a manual transmission already have the three frame bracket mounting holes punched into the outside edge of the frame. The holes are not tapped, but rather utilize self-tapping 5⁄16-12 × ⅞ screws (longer if using two brackets). An installed frame bracket can be seen in Figure 3-11. An alternative to the self-tapping screws is to tap the punched frame holes for 5⁄16-18 bolts. After tapping the punched frame holes, Lee Josephs mounted his frame bracket using 5⁄16-18 × ⅞ bolts with serrated heads (from a 7.5-inch differential cover) to remedy his problem of perpetually loosening self-tapping screws.
When using a reproduction frame bracket, the holes to mount the bracket to the frame may need to be drilled by the purchaser. In order to preserve correct clutch linkage geometry, I have created a template for marking the location of the mounting holes. The template was created from a factory frame bracket and can be found in Figure 3-12. Print the template to paper, cut out the template, apply the template to the reproduction frame bracket, mark the mounting holes, and drill the holes.
Most of the frame brackets that I have seen have been cracked. When I first noticed that the frame bracket in my 1979 Malibu Wagon was cracked, I ground the crack into a groove and welded it. Some time had passed when I noticed that the bracket had cracked again. The only remedy (aside from converting to hydraulic linkage) is to strengthen the bracket by welding two frame brackets together (Figure 3-13). The ballstud is just long enough to pass through the modified frame bracket and the nut. Lee Josephs states that the 5⁄16-18 machine screws mentioned earlier are long enough to pass through two brackets that have been welded together.
3.1.5. Lower Pushrod
There were two different design lower pushrods. The first design consists of a threaded stud and a piece of tubing. One end of the stud presses against the clutch fork and the other end threads into the tubing. The closed end of the tubing is bent 90°. At the end of the bend is a pin that inserts into the lower lever of the bellcrank. The second design (shown in Figure 3-1) consists of a threaded stud and a swivel. The stud presses against the clutch fork and the other end threads into the swivel. The swivel has a pin that inserts into the lower lever of the bellcrank. The second design obviously is cheaper to manufacture and repair, but does not contain any features to extend the service life of the part.
The swivel wears rapidly and luckily can still be purchased from GM. Shortening the stud and replacing the swivel with a female spherical rod end seems like a simple modification, but I have not yet tried it. Probably the best solution is to use the lower pushrod sold by Speed Direct (Figure 3-8).
John Bzdel manufactures and sells a clutch pedal as a companion to the 1978-1981 A body brake pedal (retaining the stock 1978-1988 A/G body pedal bracket), but designed it for use with the 1984-2002 F body hydraulic linkage. The pedal package includes all necessary installation hardware including new bronze bushings for the pedal to ride on. The pedal design retains the use of an OEM 1978-1981 A body clutch pedal pad, however, the pedal pad must be purchased separately. More details on installation are available on John's website.
With modifications, it is possible to install the clutch and brake pedals from a third generation F body.
Rob Luke recommends using the clutch master cylinder/slave cylinder assembly from a 1994 F body. The 1984-1992 assembly can be used, but utilizes a plastic hose between the clutch master cylinder and the slave cylinder, which can easily be damaged by the exhaust system. The 1994 assembly, which costs ~$40 USD less than the 1984-1992 assembly, incorporates a braided steel hose instead of the plastic hose of the earlier design. The braided hose is also longer than the earlier design, so it can more easily be routed away from the exhaust system.
Originally Released 11 February 2002
updated 02 April 2010
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Copyright © 2001-2012 Marc Hichens