Well my trans was rebuilt by Roger who also makes the gears. Every A604 should have an aux cooler even if still stock. According to Roger the overdrive is really hard on the trans. The gears may actually make it run cooler with less wear. I dunno.
There's a guy on ASEC that has them and drives a lot of highway but he's got a built trans and huge cooler.
The way I see it an A604 is gonna break sooner or later (especially if you're hard on it) might as well get the most out of it. Now if I start breaking transmissions every 10,000 miles, I might change my mind. Or not
