Over time, rearward thrust of the gear train causes the roller bearing snap ring to wear into the housing. This causes increased overall end play, which can lead to damaged hard parts or transmission failure. The repair shim locates the snap ring to its original location on a used housing. Replacing a worn housing with a new one and installing the shim to prevent snap ring groove wear is the ideal fix. This shim is included in all Goerend Rebuild Kits.