There is a dipstick you can buy. Then what you'd want to do is check the fluid level when the vehicle is cold and score the dipstick for your "cold" mark, and then check again when its hot and score the dipstick for your "hot" mark. Then you can drop the pan, change filters, etc and use that dipstick to get your fluid level back to where it was without having to hook up a scanner to read trans temp.