For greatly improved input sprag and Forward clutch durability, Sonnax heavy-duty shift valve 77754-41 for 4L60-E, 4L65-E and 4L70-E units will apply the overrun clutch in D3 1st, 2nd and 3rd gears. Remove and discard the OEM 2-3 shift valve.
Come with directions. Easy to dill 1/8" cross over hole in valve body. Now I, can pull out in low, 2nd, 3rd. gear and can down shift threw all gears and (Not hurt the tranny:) IN other words can also use all gears to help hold vehicle at a steady speed downhill. Sorta like a engine brake to help maintain desired speed.