Well... if it helps,
I changed my trans and diff fluids to red line, plus I change the trans mounts. when the car is cold shifting is notchy, but after few mins everything works smoothly.
OP - Def shift from 1st to 2nd at around 4k... let the clutch out a bit and give it a bit of gas and then let it loose :-) that helps to smooth my shifting/driving.
Just practice and see what makes sense to you. everyone is different.
Good luck....
