Originally Posted by BenzRepair

Sorry, it's the seal ring for the B1 (front) piston; I was way out of line there...

Done the job on the car a few X's, not convenient, but doable. The pin (dogbone) for the apply side of the B2 band/piston likes to fall out of the piston, so either use transmission grease to hold it in place on the B2 piston, or leave the valve body off until you insert the piston/dogbone in. You also might be able to use the next size up dogbone to take out any excessive slack in the band (need to check your book for clearance measurements... involves installing the B2 piston and cover, and measuring distance from slack to apply, or distance measured when you push on the band from beneath in your case); you can confirm dogbone size by counting the # of rings at the middle of the dogbone -- next size up has one extra stripe than what your existing one does. I believe there are 6 different sizes; the shortest one has no rings, and the longest has 5.