A manual transmission swap is fairly involved. I apologize but I don't have enough time to get into it. There are some good articles available, they should be searchable with Google or another search engine.
It is best to remove the torque converter to change a gear box on a Nissan. This will help there to be a smoother time adjusting the gear box.
why is my 2006 Nissan altima gear shift stuck in park
My 1998 Nissan sentra wony shift into high gear
because that is just the type of car that does that.
how do you change the light on the gear shift of a 2003 Lincoln navigator
A bad transmission gear can cause your 1999 Nissan frontier to shift hard. Low transmission fluid can also cause the transmission to shift hard.
could you be more specific?
your abs sensor on wheel thier are 4 dis connect 1 at a time and drive it
light is out in the gear shift area between the seats,how can I change it?
The most likely cause is a failing shift lock switch in the center console. This switch prevents the gear shift lever from moving until the brake pedal is depressed.
Bad synchro.
if it is an automatic leave it in overdrive. the transmission knows when to change into the overdrive gear. if it is a manual listen to the motor. if you have in overdrive and it bogs down while accelerating then down shift to a lower gear.