As I recall that cork gasket is # 4516 that fits as one piece inside the rounded lip of the split clamshell halves,
NOT as shown in above photo. I replaced my cork gasket with the aftermarket version (blue) shown in Post #8 here below. It does a better job of sealing over the long term, in my opinion.
https://www.ebay.com/itm/25125522858...Bk9SR6Dc0oXNYw
Don't forget to install the thin paper gaskets before sliding the torque tube drive shaft splines into the U-joint/ transmission. Also, make sure the grease fitting on the lower clamshell faces downward toward the ground.