Investigations
REAR BRAKE LOCKUP
NHTSA Engineering Analysis EA84027 - closed, opened 1984-08-28.
NHTSA investigation EA84027 is a Engineering Analysis opened on 1984-08-28 and currently closed. The subject is tracked inside the Office of Defects Investigation queue. Latest activity on this investigation was logged on 1987-09-04 - NHTSA updates that field whenever an Information Request goes out, a supplement is filed, or a status change is recorded in the public docket.
An Engineering Analysis like EA84027 is the deeper technical phase that follows a PE. NHTSA requests design, warranty, and field-failure data from the manufacturer, conducts its own testing when needed, and determines whether the evidence supports a safety defect finding that would compel a recall.
Investigators summarized the matter as follows: "SUMMARY: THE PROPORTIONING VALVE WAS CHANGED FOR 1983 MODELS (470 PSI TO250 PSI SPLIT POINT) TO REDUCE REAR BRAKE TORQUE. GM CLAIMS THAT BRAKINGPERFORMANCE MAY BE LIMITED BY TIRE TRACTION ON AN UNLOADED VEHICLE WITHNEW U..." Investigations are the early-warning layer of the federal auto-safety system, sitting upstream of formal recalls and defect orders. Whether this one closes without action or escalates into an Engineering Analysis, the full history stays in the ODI archive so researchers, litigators, and buyers can pull the paper trail at any time.
Investigation Summary
SUMMARY: THE PROPORTIONING VALVE WAS CHANGED FOR 1983 MODELS (470 PSI TO250 PSI SPLIT POINT) TO REDUCE REAR BRAKE TORQUE. GM CLAIMS THAT BRAKINGPERFORMANCE MAY BE LIMITED BY TIRE TRACTION ON AN UNLOADED VEHICLE WITHNEW UNBURNISHED LININGS, BUT BRAKING BALANCE IMPROVES ONCE THE LININGSHAVE BEEN BURNISHED AS A RESULT OF NORMAL USE.ANALYSIS: TESTING AT ETF SHOWS THAT BRAKING PERFORMANCE OF AN UNLOADEDVEHICLE WAS IMPROVED BY USE OF THE 1983 PROPORTIONING VALVE BUT BRAKINGEFFICIENCY WITH THE 1982 CONFIGURATION APPEARED TO BE ACCEPTABLE (79% TO90% ON LOW FRICTION SURFACES).STATUS: CLOSED 9/4/87.===
About This Investigation Type
An Engineering Analysis (EA) is the in-depth phase following a Preliminary Evaluation. NHTSA engineers conduct testing, collect data from manufacturers, and perform detailed technical analysis to determine whether a safety defect exists. An EA may lead to a voluntary recall by the manufacturer or, in rare cases, a mandatory recall order.
Data from NHTSA Office of Defects Investigation. Cross-references: NHTSA recall campaign API and NHTSA FARS where fatality records overlap. PlainCars does not rate or recommend vehicles. about how PlainCars sources NHTSA data.
Read our methodology - how this data is sourced, computed, and verified.