Before the latest updates cars were great, gears switched quickly and realistically, once up to 35 MPH I could set the cruise control and cruise in 3rd gear at 1500 RPMs or something like that, just as in real life.
Now the cars gears are very long, it takes around 60 MPH to hit 3rd if I'm remembering correctly and setting cruise control does nothing to lower the rpms, in fact, when I set the cruise control the RPMs surge up on their own with no input from me, I can be doing 5 MPH and the RPMS surge to like 3500-5000 rpms.
Only mods I have are "Fashion montage: start with any outfit" and "Cheat Menu"
Car I was in when this happens was the Dash Rancher, but I started a new game to try and recreate the bug and it was the same when in a Masterson Horizon, both standard models, I've yet to test heavy and sport type cars, I'll have to do that next time.