The purpose of this SAE Recommended Practice is to establish guidelines for the automatic transmission and hydraulic systems engineer to design cast iron sealing rings and select acceptable width, thickness, coatings, and other accepted design details.
This document is published as Stabilize – the technology has not changed and does not need to be updated.
Cast iron seal rings continue to be utilized in current transmission architectures though polymeric seal rings have significantly reduced their usage. At the time of this document’s stabilization, the most common application for cast iron seal rings is when the bore material is of aluminum or other non-ferrous material that is susceptible to wear if the seal ring rotates. The advantage that cast iron seal rings offer is the added radial force generated by the compressed seal ring. In combination with the pressure differentials created within in the seal groove, the seal ring’s spring force will keep the seal ring stationary with respect to the bore, minimizing any wear of the bore.
Historically, the polymeric seal rings utilized in the industry typically contain fillers that can be abrasive to aluminum and other “soft” materials. Usually, this is not an issue for iron or alloy steel bores where polymeric seal rings find most of their usage. There are efforts within the industry to reduce abrasive qualities in polymeric seals, which may even today be further reducing the use of cast iron seal rings as sealing elements within automotive transmissions.