Hi awsomepetlover,
You have to phase out the treats, not just suddenly stop them so it may take some retraining on a daily basis.. You ask for a sit, he gets a treat, ask for another sit, he doesn't get a treat, next sit give him a treat again. You want him to never know when the treat is coming, but to think that he may get one if he does sit. In place of the treat really give big praise.
dog training consultant
24 years training & behavior,pet first aide, Therapy dog eval., PA Animal Response Team