I have over 10 gallons on my Hyper 8 and about 4 on my 8.5 and never had a problem with leaking on any of my diffs. I do replace the seals about every 5th time I go into them. Are you sure it is the o-ring under the crown gear ro the ones on the out put shafts?

I have so much RC stuff I am going to sell my Hyper 8 pro as a roller with some NICE up grades.