The easiest way to replace gasket is to remve the rear end from your Cub.
A Service Manual comes in real handy to remove the hydro pump in your 1650. Don't have a service manual????? One can found in Only Cub Cadets techincal section:
http://ccmanuals.info/pdf/86_1650service.pdf
Page 2-42 has the needed infomation on removing the the rear end from your 1650. Once the rear end is removed the bolt behind the brake arm can be removed.
I will remove the 2 bolts in the rag joint when I disconnect the driveshaft instead of removing the pin.