Weird to me, but probably a symptom of something else. My 1982 300 SD has ample brake fluid, and no signs of leaking. Car stops as designed when moving forward. However, when I back up, there is very little pedal movement (unlike the normal pedal movement when braking when moving forward) and the pedal feels firm to solid. Car stops as intended in both directions, but the firm pedal in reverse has me wondering?

Any ideas?