D4 7u noise in reverse

I fired up the d4 today as I hadn't had it running in a few months. Everything seemed fine except I noticed that when I used reverse, I noticed a high pitched whine noise. Only happens in reverse? Not positive but also may have noticed a hot brake/clutch type smell but may have over analyzed things a little. Seemed to move fine in reverse aside from the noise.
I then removed the trans dipstick and noticed a bright eroded half circle notch about 3/4 in diameter in the side of the dipstick! Never noticed that before-not sure if it's always been there but it did look like it was "fresh" from being ground upon. Dipstick didn't seem bent, maybe just a little bit, and I had already shut the tractor down, but next I will remove the dipstick when it's in reverse to see if that was what the sound source was.
Is it possible that this sound could also be from an out of adjustment clutch? I do need to adjust it because it has almost lost its over-center snap in, and I sometimes need to hold the clutch lever back to keep it engaged while using the dozer.
Any ideas?