When you change the spin on filter on the allison do you need to fill it with trans fluid first?

Probably not, but I do.

Im going to change mine for the first time hopefully tomarow will any fluid overflow when i take it off just want to be prepared if it will

Filter is mounted dead vertical. It will contain about 4-1/2 ounces of fluid. There will be maybe a couple more ounces that will drip from the connection after removal, but no real flow. Make sure you remove the ring magnet from the top of the removed filter or up around the filter stud if it stays up on the trans. Wipe it off well with a clean rag or paper towels. Wipe off the filter seat on the trans, fill the new filter with clean ATF, install the ring magnet and make sure you tighten it to the recommended 1 to 1-1/4 turns after gasket contact. If the new filter was full when installed, you should not see a measurable drop on the dipstick and will require no additional ATF. Filling the new filter is also important to prevent a slug of air from being sucked to the tranny pump (immediately downstream of the filter) and being circulated through the system on startup.

Thanks idle chatter