might try giving hydrogear tech support people a telcon - check their website for phone numbers..
also - if tranny is not mechanically damaged - might just remove from tractor - turn upside down - let old oil drain out (catch it all so you know how much came out - will take a day or so for old oil to drain out completely) -refill with fresh oil (hydrogear website should tell you oil specifics) - remount - run thru an air purge cycle. above all - WORK CLEAN! - no dirt,etc. allowed into tranny cavity. take pixs during disassy so as to know how to put back together right.
Good luck.