Transmission Plates and Asbestos Exposure

Summary

Transmission plates are vital parts of automotive and mechanical drive systems. Commonly called clutch plates, these mechanical friction devices control force between an engine's flywheel and a manually operated transmission. Clutch plates are an intermediary in transmitting energy to wheels or tracks and propelling a vehicle. These rotating discs take a beating from heat and abrasion. To control heat and friction, all clutch plates manufactured before 1980 contained deadly asbestos fibers.

Since the invention of the mechanical self-propelled equipment in the late 1800’s, transmission and clutch plate manufacturers chose asbestos materials as the ideal additive to make clutch discs. Asbestos was durable and withstood constant grinding from slippage while an engine and transmission engaged. Asbestos was fireproof which was important given the high heat driveline friction forces produced. Asbestos was also widely available, stable to blend with other products, and very inexpensive to purchase.

Asbestos Use in Clutch and Transmission Plates

Clutch plates varied in size depending on the application. Passenger vehicle and light truck clutch plates ranged from 10 to 12 inches in diameter. That converted to about 10 square inches of exposed friction surface per disc. Given that clutch plates were an approximately ½ inch thick, a clutch plate weighed around four pounds. Many clutch plates contained up to 50 percent asbestos material by volume, meaning that millions of microscopic asbestos fibers were bound up in one small item.

Transmission plates increased according to the size of equipment. Heavy-duty semi-trucks had clutch plates exceeding 2 feet in diameter while big equipment like Caterpillar bulldozers had clutch plates weighing a hundred pounds or more. That was an incalculable amount of asbestos fibers under strain and wearing away.

Clutch plate manufacturers used two types of asbestos for making discs. The most common asbestos form was chrysotile or white asbestos, which was the least harmful asbestos classification. The other was amphibole asbestos that ranged in colors like blue, green and brown. Amphibole asbestos fibers are especially dangerous.

Manufactures blended both asbestos fiber types into transmission plates and balanced their ratios according to the stress they anticipated the plates would see. Most car and pickup clutch plates had high proportions of chrysotile fibers compared to amphibole particles. The reverse happened with heavy-duty equipment. Clutch discs on tractors, loaders and graders were mostly constructed of amphibole fibers making asbestos exposure more dangerous for heavy-duty mechanics than those who did light duty repairs.

Asbestos Exposure from Clutch and Transmission Plates

Car drivers and equipment operators had no real risk of asbestos exposure from asbestos-containing clutch plates. Even though clutch discs were shedding asbestos fibers through daily use, fibers were blown away or trapped inside the clutch compartment or what’s called a bell housing. It was mechanics who got blasted by airborne asbestos fibers when they opened compartments and released millions of microscopic particles.

Clutch plate manufacturing workers also suffered long-term asbestos fiber exposure when handling raw chrysotile or amphibole asbestos materials. Unless the factory and its workers took careful precautions with respirators and protective clothing, clutch disc assemblers daily worked in an environment filled with airborne asbestos fibers. That turned out to be deadly.

MJN Brief

By the 1980s, the Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA) had banned asbestos products in clutch plates. They also prescribed strict protocols for protecting workers who still faced working on equipment containing asbestos-faced transmission plates. Those rules only applied to accredited repair shops. Left on their own were farmers, truckers and home repair mechanics.

 

Mesothelioma and Asbestos Exposure from Clutch and Transmission Plates

Mesothelioma is a fatal lung disease that’s only caused by airborne asbestos fiber exposure. When workers inhaled air containing asbestos fibers, these tiny particles attached to the lung lining or what’s known as the mesothelium. Spiky amphibole fibers were more prone to embedding in the mesothelium than softer chrysotile fibers.

Regardless of type, asbestos fibers stayed in the mesothelium. Scar tissue formed over fiber clumps and turned into cancer tumors over long periods of time. Mesothelioma is this deadly disease, and there’s no known cure for advanced stages.

Compensation for Mesothelioma Victims

Law firms represent mesothelioma victims to collect compensation from negligent asbestos manufacturers of clutch plates and other asbestos-containing materials. Many asbestos suppliers and producers knew that they were exposing mechanics and factory workers to lethal levels of dangerous asbestos fibers. Now, manufacturers must compensate mesothelioma victims for medical expenses, personal injury damages and lost income. Families of mesothelioma victims can file claims on their behalf. They can also sue in wrongful death cases.