Assuming you have a typical stock governor, you should be shifting into 2nd around 10-12 mph, 15 tops, then shifting into 3rd around 20-25ish or so then into 4th around 35-40 and lock up should occur shortly thereafter unless you either hit the brakes or accelerate further. If you have another, perhaps newer GM truck with a 4L60E and dash tach, shift points/timing are largely the same so you can use that other vehicle for reference.I'm glad you brought that up because that leads me to my next concern. I have my cable end clamp installed to where the TV cable is about as tight as i can make it, it seems. Since I have no tach, is there a speed range I can use as a reference for shift timing from 1-2, 2-3, & 3-4 instead?
My main concern is my 1-2 shift, It seems to be bumping into second gear under 10 mph