It really depends on the different dogs’ temperament. Your pit may be fine, but the chihuahua mix may not be, or vice versa. My pit is a sweetie, but my friend’s chihuahua is not so great with other dogs. If both your dogs are usually ok with other dogs, you should do a test introduction. Google the most effective ways to have a successful meet and greet. Some tips include meeting in a neutral location, not on either dog’s territory, walking the dogs together, etc. Good luck.