Weird uprev issue, quick burst from 3000rpm to 4000rpm

Diablo3

Yesterday I was driving over a mountain (for those that live in Huntsville, it's the one that divides Hampton Cove from Jones Valley).



Long stretches, long straight aways....at some points along the drive, as you're driving 65, 60....etc, the road dips down, so you have to naturally break to slow down to not hit the car in front of you...or to keep a safe distance.


However, about 3 times this happened yesterday.
When I was around the 65 mark, holding the break in to slowly slowdown, not a slam break...the car went from 3000 rpm's to 4000 rpm's for a split second, then it went back down to 3000 rpm's....Figured it would of been masked a little better,it was pretty noticable.


What could cause this?
Only happened during situations like the one described above, 3 times throughout thedrive on the mountain, both ways.......


Touring automatic '12 Z