The larger o-ring wasn’t there when I removed the old filter. . Next time it will just be a drain and refill operation. If the trans goes bad it is getting a 5 speed swapped in.
Currently, when cold it shifts late and a bit hard going into 4th gear. When warm it shifts nicely. The fluid was like black coffee. I’m hoping some new fluid helps cold shifting. After a couple thousand miles I likely will drain and fill it again to get more of the old stuff out.
Your shifting problem is probably because your throttle valve cable is out of adjustment. That bullet or collet on the cable ( at throttle) needs to be off the rest or end of cable housing, but not by much. I’m not sure if there’s a spec for how far off the cable it needs to be.
I just eyeball the thing. Then I leave the nuts finger tight. I drive the truck and like to adjust the cable till the last shift( actually the last time the torque converter clutch engages) happens at 52 mph under light load. When I get that to happen I’m usually happy with all the other shifts.
Boxter is right on time with his advise on the o ring placement. The fact the big one was missing is troubling but not surprising.
As far as your getting that crossmember out you need a little porta power. I have a pretty cheap one and it works. I would like to have a nicer one but really all you gain is less weight. You get that up between the frame rails and push them apart. You need to keep your hand on the crossmember so it don’t fall out and hit you in the head.