Kickdown linkage
So it winds up to far before it shifts and as you slow down it down shifts
real fast and to soon ?
If so it sounds like it is to long. Some one will jump in here and help that can help, But if I am reading you right you can shorten it easier then lengthen it.
But you should wait on a tec to chime in.
I don't think I welcomed you to this great site yet.
Glad to have you aboard Sinister.:-D