A steel wire spring ring retains the lip seal in the speedometer gear module. The seal is GM part # 1240382 which is available at GM dealers. The O-ring is a #117 (.103? diameter with a 1? outside diameter). The groove in the housing is .826? which leaves the O-ring proud when installed The rubber lip seal is a one-piece design with no tension spring, depending on the resiliency of the material to keep lip pressure on the speedometer driven gear shaft. With age and wear the seal will lose tension and pass minor amounts of transmission fluid producing an annoying drip