Fill a large pot with water, add a generous pinch of salt, and bring it to a boil. Measure out all ingredients and chop the dill if using.
Add the 3 cups rotini pasta to the boiling water and cook until al dente, about 10 to 12 minutes. Drain the pasta and rinse under cold water to stop the cooking.
Dice 1 cup dill pickles and shred 1 cup cheddar cheese if it isn’t pre-shredded.
Make the dressing
In a small bowl, whisk together the 1/2 cup mayonnaise, 2 tablespoons pickle juice, and a pinch of salt and pepper. Taste and adjust seasoning as needed.
Toss and chill
In a large mixing bowl, combine the cooled pasta, diced pickles, and shredded cheese. Pour the dressing over everything and gently stir to coat. Cover and refrigerate for at least 1 hour before serving. Sprinkle fresh dill over the top.