I bet you busted a seal... Also make sure the ridges on the intermediate point outward... it goes like this.
Bell shaped servo, servo with ridges or notches facing out, then little servo, then cover.
Any tranny shop can sell you a seal kit for like $15 or less. Remember every time you remove the cover, you have to replace the cover o ring. Unless some how you can remove the cover and o ring without damaging the o ring, yet it still retains its function.