99 GTP shift question

[GTP78]

I have a 99 gtp supercharged , automatic(just got it) when it shifts from 1st to 2nd its shifts at about 19mph but when it shifts from 2nd to 3rd it doesnt shift till about 46mph is this right. This is with normal driving not heavy on the pedal. If I take it for a drive and hit about 53mph put it down in to 3rd and it jumps from around 1500 rpm to 2500 rpm's. So im not sure if 3rd is going out or is gone or what is going on.

[BillBoost37]

1500 at 53 would be 4th gear. Put the selector in 3 and go for that same normal drive. I am thinking you won't get a third shift.