03 chevy blazer transmission detent cable adjustment

If this is an 03 Chevy Blazer with the 4.3, there is no kick down cable, it is all computer controlled using the speed sensors and the TPS.

Now if you mean the shifter cable that connects the lever in the cab to the trans. There is a clip on the trans end. You put the vehicle in park, the push the clip in and slide the cable housing toward the shift lever on the trans. Release the clip. Turn on the key and pull the shift lever all the way down to the low stop. The cable will adjust itself and you should be all set.