Sound issue, possible glitch. Any ideas?

Right so this is an issue ive noticed for a long time maybe even since FH2 came out and it is that i can be driving and the revs will stay at a few thousand the speed will gain then the revs suddenly jump up to being normal, this occurs on pretty much any car stock or not. Not sure whether this is a glitch or its just my console/game. Anybody else experienced this issue?

Been around since release and affects pretty much evryone and no way to fully fix it. There are several threads about it hiding in here.