it's going to cause your tranny to go quicker than it would normally.... it's not meant to be driven like that.
(i know... i had a 99 GT 4EAT)
u may want to consider adding a tranny cooler.
this may help keep the tranny fluid cooler...
(mine boiled over from manual shifts.... a lot)
eventually, it will take it's toll..
but no Tranny lasts forever