Transmission shift point(s)?

[magnethead]

What are the general shift points on a TH400 when mated to a 454?

On our truck, when you first lay into it from a dead stop, it'll start moving, then at about 12 MPH it makes a HARD jerk, and judging from the engine sound, I assume this is the first-second shift. Then about 20 MPH, if youre foot is really in it, it'll jerk hard again, else it'll do it unnoticablely. And by Jerk, i mean 18 wheeler fully loaded jerk...it rattle's your brains..and for the first shift, it doesnt matter where your foot is, shallow or WOT, it still does it hard.

Is 10 and 20 MPH about right under mild acceleration for shift points (i know the TV cable makes it somewhat variable).

FYI based on my calculator:

12 MPH 1st gear = 1400 RPM
12 MPH 2nd gear = 800 RPM
20 MPH 2nd gear = 1400 RPM
20 MPH 3rd gear = 900 RPM

so is it safe to assume the transmission will normally shift at 1400 RPM?

calculator: http://www.auto-chat.net/help/textgraph/index.php