I recently did a trans fluid and filter change on my 04 Regal with the 4t65 (just a pan drop, not a flush). First one, at 118000 files. Fluid was, as might be expected, a bit on the brownish side but there was no material in the pan other than some fine gray material, which I understand to be "clutch mud" and also to be expected. Here'* the issue -- when I removed the old filter, the seal came out with it (attached to the filter neck). That was nice, since I did not have to extract it myself. So far so good. But I could not get the seal that came with the new filter all of the way into the pump. My bad- I had not sufficiently done my homework and did not know that the new seal needs to be tapped into place with a socket. So I used the old filter seal. it was still fairly tight, but for the life of me I can't remember if I got it fully seated all the way up. So now I'm worried that the filter seal might get dislodged at some point. On the other hand, the filter didn't fall out after I put it into place prior to reattaching the pan. And I was able to reattach the pan, and it'* my understanding that if the filter isn't all the way in that the pan won't go back on. Plus, I've read that the filter is primarily for capturing material during the break-in period. And since the filter is so close to the pan, even if the seal were to dislodge it would still be on the filter neck and the filter would remain in place because it'* essentially sitting on the pan anyways (although its function obviously would be compromised). The transmission seems fine. So... given these circumstances, should I drop the pan again? I hate to re-do this job, but this is bugging me.

I think you will be ok, but with that kind of mileage before the first change and only a pan drop, at most you only changed out about 55% of the old fluid and it certainly wouldn't hurt to do it again especially if it gives you some piece of mind. Hopefully you used Dex VI.

2004 Bonne SLE
1971 Chevelle SS

I think you are okay, but be extra sensitive to any shifting issues for the next little while.

Plus, I've read that the filter is primarily for capturing material during the break-in period.

If that filter is not completely attached, that "mud" and any metal(big/small)in the bottom of the pan could be sucked into the valve body.......that'* why the filter is there...that'* why the filter is changed.....

Thanks for the replies. I used the Valvoline MaxLife. There is only one type, and Valvoline claims it is compatible with all Dexron applications. I also have read other posts where folks seemed to have good results with it in the 4t65. Another thought on the seal -- the seal should be all the way into the pump body, right? In the videos I have been able to find, it looks like it is all the way in (i.e., that no portion of it is sticking out). Also, if I recall correctly, the filter neck is constructed such that the seal can go down only a certain portion of the length of the neck, and then stops. (I might be wrong on that, though.) But assuming that is the case, does this mean that since I was able to properly seat the filter before attaching the pan (i.e., it stayed in on its own and did not touch the pan), that the seal necessarily was fully seated in the pump? In other words, if the seal is not fully inserted into the pump, it is impossible to insert the filter far enough to be able to reattach the pan? Also, curiously, I was able to extract 8 quarts (in addition to what I spilled on the floor) even though the car'* manual lists capacity for a pan drop as 7.4 quarts.

The Valvoline is a synthetic..meets Dex 6..but I would rather use straight Dexron 6.
http://www.valvoline.com/pdf/maxlife_atf.pdf
When I did the Pk Ave pan drop, I always expect more fluid to be replaced.
I think I also used around 8 quarts of Dex6. My next fluid filter will be at 40k miles next.
Based on what you have described, I think you have seated the filter ok...
Like mentioned just make sure your shifts are ok and carry on...
Check the fluid levels when hot for a few weeks, I generally keep mine just above the full mark, after a hwy drive of 20 min plus, of course in park, running on level ground.