This may not be of any help to you, but in years past, Snapper has used the Eaton transaxles.  I used to own a Snapper Hydro that had the Eaton 850 transaxle.  I realize the 650 and 850 are completely different, but that suggests to me Snapper may have used the 650 in a smaller/lighter duty model.  The Snapper Hydro I owned was an early 90's model.  Hope this helped. :thumbsup: