This is the 5th gear on the countershaft for the 5 speed NV4500 transmission in a Dodge or Chevrolet. This gear has 51 teeth, 6 1/4" diameter and is for the 5.61 high ratio transmission. This gear is the only option for a Dodge and will only work with the Chevy when the 5th gear on the mainshaft has 22 teeth., if your 5th gear has 19 please see my other listing.  You can identify this transmission in a Dodge by the cast "C-18157" or "C-23167". This transmission has an iron case with an aluminum top cover! This transmission usually comes in the 1994-ON Dodge Cummins Turbo diesel truck. You can identify this transmission in a Chevy by the cast "C-16812" or "C-18157". This transmission has an iron case with an aluminum top cover! This transmission usually comes in the 1990-95 Chevy 3/4 ton or 1 ton gas and diesel trucks.