shift kits are awesome

my uncle has one in his dually set up for heavy duty and man the shifts are perfect it'll hold any gear to any rpm

full competition means they wont downshift unless you do it manually
heavy duty is good for off road and towing
street/strip is pretty obvious

but if you want name brand the Transgo one is like $110

PATC makes a few under $70

but yeah supposedly those soft shifts are harder on the trans than a nice firm one
so i guess technically it'll help ur trans last longer

plus most of the kits for our trans fix that "torque converter not charging in park" problem

 

how do install a shift kit... is it like an external mod.. or do you have to have a tranny shop do it?

 

when my tranny bit the dust I had a small shiftkit installed on mine. From what I understood the shiftkit changes the valves in the tranny itself, making the shifts harder. I know that after mine was installed the shift points had changed and there was not a smooth shift left in the old beast.