Of course, they all claim not to be partisan. But on partisan issues, the votes of 7 of the Justices are completely predictable (usually).
A lot of issues they decide have no partisan issue involved, most in fact. We rarely hear of them.
And there is of course a philosophical difference in opinion here, some are Originalists and some think their judgment should reflect what is needed today.
I used to read some of the decisions on patent law, interesting stuff (not really) and entirely not partisan. They often ruled 9-0.