all vehicles sometimes shift up/down seemingly randomly due to gear ratios/speed.  The Vaquero specifically has an issue where where when it hits 5th gear, after a second the audio just switches to idle and it sounds like you're no longer accelerating.  Car just whirrs along sounding like its losing speed with no input and then down shifts to 4th and continues to just whirr until the vehicle needs to accelerate again.   Actually looked at the Vaquero gearing and noted that the Vaquero