Les, all my previous trucks (cept brief stint with BIII) were sticks, so this is my first regular DD with a slush box... I wasn't sure the change interval on mine when I got it, and wanted to put it to some heavy towing use... rather than pulling the pan, and getting all crazy, I simply did a little at a time. For my last three oil changes (May through to now) I've drained 4-5L of trans fluid each time, through the drain plug (the rest sits in the TC). Should be theoretically all new fluid by now, but I'm gonna do one more partial with my next oil change, just to be sure. The magic box seems to shift a little crisper now, and is smoother from a stop.

Heat is the enemy of any auto (so they tell me), and if your fluid is breaking down, then it can't dissipate heat as quickly, can it? I say change it a little at a time, and get another 172k miles out of it.

(should be taken with a grain of salt, since I'm still trying to figure out what "PRNDL" stands for. <img src="/forums/images/graemlins/scared.gif" alt="" /> <img src="/forums/images/graemlins/drunk.gif" alt="" />)