Until I logged into this forum, I had no information about the spin on filter for the Allison trans. I've looked high and low in the owners manual, and the additional brochure for the allison and nothing is mentioned. I have changed the fluid and internal filter and external (had chev dealer do it) along with a fluid flush, which was recommended by the dealer at 26000. The dealer wanted to know if I wanted them to change the spin on at the same time, and I replied that if I didn't have it done, it would be like taking a shower and putting the dirty clothes back on.Excactly
Also if you have an auto trans you shoul change your spin on filter pretty regular also some where between 6 and 10,000miles dependingon how u use your truck. With thenew uls diesel out now i hlps to run some sort of fuel additive in every tank!!!