That Dana 6800-1 (made in Taiwan) also has a chain inside, many have went down grades & the slack gets loaded up & pops a hole thru that case. Dana sold their name to this transaxle maker. But later wanted to take em to court over the crappy unit they made.
My last tractor had that tranny & same issue at both axles. sears said they don't have repair parts, they just replace them. The parts were obsolete just as my warranty expired.
Try this: if you can wiggle the axle end, NO SEAL is gonna stop the leaking. They ride on the aluminum housing & that wears out quickly.
There is a fill plug under the belt pulley, I used to add STP just till I could get all the Peerless parts I needed.
I finally switched it over to a Peerless tranny, which was pretty simple swap & way better unit, & sears really shaved the prices of the parts I needed after I filed a complaint with BBB against sears.
If you google up this model, you may likely still find a long line of owners that are pizzed about this unit. Save the headache & switch to a Peerless. Mine operated flawlessly.