The piston bore in 4T80-E units is prone to wear, either through normal operation or uneven loading from the spring. The Sonnax replacement piston 72871-01 provides more piston-to-pin support and greater durability than OE replacements.
This piston should not be used in a first-design 2-3 accumulator found in '93 models. These units do NOT have the second bumper spring on the top portion of the accumulator piston. If the large spring is broken, replace with GM part number 8684828