Allison 1000/2000 & Internal 1st Design 2wd or 4wd (Shallow Pan) Black Filter Fits: Late 2006-On The internal filter should be changed and the pan dropped periodically to ensure that this filter has not trapped metal filings which are a tell tale sign of an internal problem, especially when towing a hefty load. Every 60 to 70K miles is a good time to consider doing this flush. Cheap insurance is better then an expensive rebuild that could have been prevented.