On a 4T65e, shift times can be set "sorta" quick, though I wouldnt set it much faster than the .175 factory time on the 2-3 shift. 1-2 can go down some and leave the 3-4 stock is fine. Adding line pressure is good way aswell, like 5-10% because anything more will just start to clunk into gear and not be as smooth.
But in something like a 4L60e or similar, it's alot different. Going past .275 isnt such a good idea, but .300 is great. Seeing how stock times are near .500 and .600, then adding slight amounts of line pressure again to achive the rest.
Then get into something like the 6L80e in my truck, talk about crazy amounts of tables and stuff that can completely fubar the whole shifting if you do it wrong. It's a clutch to clutch trans and everything is electronically controlled.
