Your Trans. IS serviceable, many members do their own repairs and re-builds. What is needed is the trans info. from your unit , make, model, ID numbers ... sticker, tag, or plate should be on side,or bottom of trans ,but some are on top also... here's a sample :
View attachment 32602 ..click here
https://www.surpluscenter.com/Featured-Items/TUFF-TORQ-K66-HYDROSTATIC-TRANSAXLE-13-1577.axd
post the info back here ... Boobala