If your cadence is not the problem, then the emphasis should move to enhancing your stride mechanics. Imagine your foot being pulled up just slightly higher off the ground, making the swinging leg lever shorter and enabling the hip flexors to pull forward with ease. This will allow your body to land while the knee is still flexed thus preventing overstriding. Initially, it may seem uncomfortable, but over time, it allows you to tune your pacing such that your footing is quieter and thus, you are more efficient in your run.