Is it absolutely necessary to add a transmission cooler with a smaller pulley? Thanks.

nope

many think trans coolers are a total waste. I think it depends on where u live.

When I moved to texas I added a trans cooler to help deal w/ the 100+ deg days.

I'm in DC. Doesn't get that warm here (usually). Plus, I'm not really stompin on it anyway. Thanks.

thank god there hasn't been but 1-100*+ day here in texas this year, still tired of the rain though.