1999 Chevrolet C/K Series problems

In a letter dated april 20, 2005, gm notified the federal safety agency that it had decided that defects that relate to motor vehicle safety exist in certain model year (my) 1999-2002 c/k 1500 series (pbr parking brake system) and my 2001-2005 c/k 2500 and 3500 series (trw parking brake system) pickups with manual transmissions.according to gm, some of these vehicles may have conditions that cause the friction linings to wear to an extent where the parking brake can become ineffective in immobilizing a parked vehicle.gm's action covers an estimated total of 142,585 vehicles.dealers will install a low-force spring clip retainer for vehicles equipped with the pbr parking brake system and install a redesigned parking brake cable assembly on vehicles equipped with the trw parking brake system. A total of 58 non-duplicative complaints were received by odi and gm concerning the approximately 59,000 my 1999-2002 c/k 1500 series pickup trucks with the pbr parking brake system.these included 22 alleged rollaway incidents, resulting in a rate of 38.5 rollaway incidents per 100,000 vehicles.odi is aware of 24 complaints regarding the my 2001-2005 c/k 2500 and 3500 series manual transmission trucks recalled by gm, including 5 alleging rollaway incidents.though the conditions described in gm's letter are also present in the c/k trucks with automatic transmissions, the rollaway rate in those vehicles was similar to those observed in peer vehicles studied by odi in this investigation.this engineering analysis is closed. For additional information, see the attached closing report.

EA04011

Odi opened pe03-057 to assess parking brake ineffectiveness in the subject vehicles.these vehicles are equipped with four wheel disc brakes that incorporate a single-shoe drum-in-hat parking brake independent of the service brakes.complaint and warranty data indicate that the parking brake linings tend to wear out early in the life of the vehicle (at an average of 24 months in service), reducing the parking brake system's torque below that needed to immobilize the vehicle.gm has attributed this accelerated wear to foreign material intrusion and a failure of the brake shoe to properly self-center within its brake drum.effective with the start of my 2003 production, a newer reduced force hold-down clip was introduced to facilitate brake shoe disengagement from the drum surface.this part is also available at the service level for the my 1999-2002 vehicles.gm has indicated that the paking brake is intended to operate in conjunction with the transmission to immobilze parked vehicles, and that in many cases, accelerated parking brake lining wear is caused by rough use, vehicle modifications, and driving with the parking engaged. Odi has upgraded the preliminary evaluation to an engineering analysis to gather further information concerning parking brake usage factors and the circumstances surrounding the seventeen reported vehicle crashes.

PE03057

Odi upgraded the preliminary evaluation to conduct a full technical analysis, including testing.the testing and analysis shows that a torn diaphragm is a slow progressive type of failure.the tear propagates in a slow methodical manner and braking performance is similar to an untorn unit until the tear exceeds 1/2 inch.odi's testing indicates that tears greater than 1/2 inch required increased pedal effort.however, as the length of the tear increased beyond 1/2 inch, a hissing sound could be heard emitting into the passenger compartment where the master cylinder plunger passed through the firewall. Odi has determined that a safety-related defect trend has not been identified at this time and further use of agency resources does not appear to be warranted.the closing of this investigation does not constitute a finding that no safety-related defect exists.the agency reserves the right to take further action in the future if warranted by the circumstances.odi's complete technical analysis with test data is attached.

EA01013