Sounds like the 2-3 accumulator. It was a common recommendation anytime you had the pan off even for a fluid and filter change to replace it with the improve cat which was another accumulator and probably the better improve snap ring. Why didn't you just have yours fixed instead of rebuilding the whole thing? That sounds high for a rebuild too but depending on the area prices to vary in different parts of the country. It's just hard to find an ethical or honest transmission shop. A lot of them don't even really know how to fix them inside anymore or there's only one guy there that does so all they want to do is swap them out with the units they have already purchased rebuilt. They often don't know from the symptoms what the problems actually are they just take them out and tear them apart and then find it. At that point there's so much money involved you're between a rock and a hard place. A broken accumulator spring and a good handful of other problems can be fixed by just removing the pan or the valve body is the next step. Neither one requires the entire transmission to be removed from the vehicle or a complete rebuild. But the biggest problem is they don't want to do a minor repair that's just a minor repair for a couple hundred bucks. They want to get the big money and rebuild them every time.