When my car accelerates to 45-50 miles per hour, it momentarily feels like I am riding/rolling over a repetitive series of "speed-trap stripes" similar to those in toll-booth zones. What may be the cause of this sensation? Also, I have noticed that when I accelerate to 55-miles per hour, my SUV does a rather "jerky" shifting thing, as if attempting to shift into another gear, and yet my SUV is not an automatic. Any idea of a possible cause?
It sounds like your wheels need to be balanced. Make sure that the tires are in good condition and then have a shop re-balance them.
As for the shifting, there may be a problem with the transmission or something with the engine that's making you think it wants to shift. I would suggest riding with a technician to show them what you're feeling so that they can properly diagnose it.
〉 Answered on Mar 14th, 2008 by Lori Johnson, Owner and Instructor at Ladies Start Your Engines