School me on trans basics

I run a 904 with a converter that stalls right at 4000 and 3:23 gears with 28" tires so even at 70 mph it's only spinning 3k. According to my temp gauge it doesn't get over 150 when cruising on an 85* day. Almost every weekend we hit a cruise and we live in the middle of nowhere so nearly all cruises are 40 miles away. A loose race converter might slip enough to generate too much heat but a decent street/strip converter made nowadays usually doesn't. Hughes converters from my experience are decent converters and don't usually slip much under light throttle