Rebuild? Or clean what can be cleaned and replace the old gaskets/o-rings? @HotRodPC @chengny @da_raabi or any other th400 guru that has some good info on the subject. Again, this is a low mileage, number's matching truck that has sat most of its life. It's only done this three times now, and spaced out about a week apart each time over the last few weeks. Leaving for work, truck still cold from sitting overnight, the pump would make a high pitched noise at higher rpm's, shift into 2nd it'd go away until the rpm's got high again, shift into 3rd and it'd go away. Next stop, drop it into 1st, take off, pump would make the noise when the engine revved, 2nd it would go away then come back at higher rpm's, 3rd it'd go away. Next stop, no more noise and it would shift normal. Even with the noise, after the second stop, which is about a mile of driving, it would shift normal whether shifting manually or letting the tranny shift. This morning I was backing out, and it was doing its shudder thing, so I stopped, put it neutral, then drive, neutral, reverse, and back and forth a couple more times before backing out. No more shudder. Taking off in 1st, the pump was making that noise but not as loud as the other two times, shifted into 2nd and it went into gear but not the solid 1-2 shift that a th400 is known for, and going into 3rd it was slipping. I put it in neutral while rolling and back into D, slip, back into N and then D, slip, drop it into 2, slip, D, slip. So I pulled over, put it in P, R, N, D and each gear was a little mushy. Reverse didn't slam like it was trying to rip the driveshaft out, and D didn't engage strong either. I was just down the street from the house so I was going to take it home and grab the Forester. When I went to take off again it was still slipping. Turned a corner and drove about another 1/mile to start back home, and the tranny was shifting normal again. So I brought it to work. No more issues. I don't want to grenade my tranny, and besides it's weird acting up from time to time, which has become less and less, it works great. Shifts are good, passing gear works, etc. I've read there is stuff I can remove and clean without removing the unit from the truck. How do I do that, or should I just pull the unit and rebuild it? I wonder if the new filter got plugged after running the conditioner in the tranny?