Thank you for your question.
If the transaxle is leaking the leak should be repaired first. If it is a slow leak, you can add as needed. Once the leak is repaired, you can fill the transaxle with 20W-50. To fill the transaxle you have to remove the breather from the top of the transaxle. I have provided you with an image below showing its location. Then fill with oil until the level is 1 to 1 3/4 from the top of the hole.
Please let me know if you need further assistance in this repair.
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