Since this is my thread, I don't really know that I can "hijack" my own topic, but I' think we're off course here, folks. However, I abhor misinformation, so allow me to chime in about the Allison.
I got my info from two guys who work at the Indy Allison facility, which is on the west side of Indy where I also work. I also knew (past tense) one of the quality engineers over there; she and I worked at Ford before we both chose difference paths.
The "main" filter (the big one inside the pan) is simply a chunk catcher in case of catastrophic degredation of parts. It's so porous it does not have a publised um rating. It functions just like most internal filters in most trannies, and sees a large volume of flow. It's only job in life is "in case of emergency".
The "spin on" filter is a "full flow" filter, but only by definition of it's design of the filter, and NOT the application it's used for. That little spin on filter ONLY filters the oil going to the valve body, but it does 100% of that flow. So, in some manner, you could call it a "bypass filter" because it only sees what the valve body sees and not the TOTAL flow of the pumped system. OTOH, it is doing 100% of the valve body flow, so it does need to have a reasonably high flow capacity and is NOT a "bypass" filter in the manner that most of us think of such a term. The um rating of the spin on (from Wix 57701) is 15um nominal. (Note - in contrast, the small "bypass filter" (Wix 57701) in a Ford 5R110 tranny line is truly a bypass filter, and is rated at 1um nominal!)
Allison's stated filter change intervals are well published on their site. The "interal" filter is only recommended at major overhauls and such; in general you should never have to change one, but many people do so in some misguided anal-rententive search of perfection. The spin on is dependent upon type fluid used (TES-295 syn or "non-TES-295" fluids). It is also dependent upon the type service factor. Note that what we think of as severe and what Allison defines as severe are two different things. Not many of us operate a vehicle such as refuse trucks or airport shuttles that never get the TC to lock up, and they are constantly flashed by heavy-footed, low-$-paid hourly people who don't care about the rig at all. THAT is what Allison defines as "severe". (I'm not picking on low dollar wage folks, but I think most of us understand that their committment to company vehicle care ends when their shift ends ... you get the idea.)
Use this page (the tranny in our trucks is the 100 series non-MH ):
http://www.allisontransmission.com/service/changeinterval/
Note that if you use a "non" Allison fluid, it will not give any recommendation, but that's obviously a marketing ploy. The TES-389 fluids are what Allison calls the former DEX III fluids. That was their "new" spec they came up with when DEX III was dropped, and they needed a non-synthetic alternative to TES-295.
Using non-severe factors, and TES-389 (dino) fluids, the "normal" lifespan of the spin on filter is 50k miles for a 1000 series tranny.
I would trust Allison's recommendation over any super-duper aftermarket-hyped speed shop any day of the week, because Allison has millions of test and real world miles to back up their data. Perhaps in an ultra-hot sled or drag truck, these change intervals may not apply, but for most of us, Allison knows best.
And don't forget that as filters load up, they become MORE able to catch the dirt you're trying to avoid in circulation.
I disagree that frequent filter changes will manifest themselves in the "best" care; they are as big a waste as using synthetic for short OCIs. And often, you'll find those two paradigms utilized by the same folks. "Normal" folks can use normal fluids and normal filters and get a very long service life out of their vehicle with normal maintenance routines. There is no "need" for more than that.
