This is a Brand New 5th Gear Nut kit for the GM/Chevy NV4500 It will only work for the Chevy if you have the Dodge please see my store. You can identify this transmission in a Chevy by cast # "C-16812" or "C-18157" and in a Dodge by "C-18157" or "C23167" This transmission has an iron case with an aluminum top cover! This transmission usually comes in the 1990-95 Chevy and Dodge 3/4 ton or 1 ton gas and diesel trucks. Note: NV4500 Transmissions are famous for 5th gear rocking off the mainshaft causing you to loose 5th. This Updated Nut kit along with the corresponding updated Mainshaft stops that problem. If have not lost 5th you will this is any easy fix or preventive measure that should be done with every rebuild.