Can you pass HPV on to your partner if you have already had the gardasil shot?

Depends. If you have pre-existing hpv infection prior to the Gardasil vaccine or if you acquire a different type of hpv (other than 16, 18, 6, or 11), you could pass it along to your partner. Gardasil protects from the 4 hpv types mentioned above, which are linked to 90% of genital warts and 70% of all cervical cancers.
Yes. The Gardasil vaccination series does not mean that you won't ever get an hpv infection. What it means is that you are more likely to clear the infection before it can cause cervical cancer.