For 4L60E transmissions with Code 1870. This kit corrects wear in the valve body that causes code 1870. The reamer is specially designed for use with our TCC regulator valve kits 77754-03K and 77754-04K. This reamer allows the installation of our re-designed TCC regulator sleeve and valve and requires only cutting oil and a speed handle. The reamer also features a depth stop to prevent over boring. This fix will not work on GM remanufactured transmissions.