I will Take Job that requires only Secret with active TS

I am about to change jobs. Current have an active TS, but new job only requires Secret.
When will my Periodic Review be? Will it be 5 years from the last TS PR or 10 years, since Secret PRs are every 10 years? Or will I have to do another SF86 at new hire?

ODNI and OPM are transitioning to 5 year updates for Secret clearance holders but it has not been fully implemented yet by most agencies, so I would venture to say your investigation for the TS will be accepted under reciprocity and you won’t have to do anything for a while.