[biketopia]

I know this is a two week late response, but when I had my 03 duramax I would do the external filter every 10k, drain and fill the pan every 25k, why my truck was used it was used hard. At the time, all the Allison documents I had and speaking with the Allison dealers they all said the internal filter should only be replaced at a rebuild. I did mine at 100k just for the hell of it but then was doing regular drain and fills with the external filter and never thought twice about dropping the pan again. Use the correct TES 295 approved fluid! Unless your trans has been built, then some builders recommend a Dex3, otherwise stick with approved fluid. Also make sure you remember the magnet, when I did the first external filter when I got my truck with 72k on it the magnet was gone...