Does your car have an automatic transmission? It sure sounds like classic symptoms of a bad torque converter...
" Shuddering – If you start to feel shudders when driving about 30 to 45 MPH, this could mean that you have torque converter problems on your hand. It will often feel like running over rough road or bumps and you will definitely notice it when it happens. Shuddering comes and goes without warning, so once you feel it the first time you should get your transmission checked out as soon as possible. Don’t wait for it to happen again."
http://www.ehow.com/about_5611225_to...-problems.html
Of course, if yours is a manual... never mind.
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2013 1SS/RS Coupe L99, Stainless Power Works LT Headers, SCT X4 Custom Tune from RDP, CAI Inc. Air Intake w/ Apex Scoop, VMAX CNC Ported Throttle Body, Solo Axle-Back Exhaust w/ J-pipes, Apex Catch Can, Husky Splash Guards, Heritage Grille, 3D Carbon Rear Spoiler, Oracle Chrome Turn Signal Bulbs, GM Reverse Light Trim Billets, Gorilla Black Locking Lugs, Emblem Pros Retro SS Badges/Custom Retro SS Kickplates/Under-hood Bowtie, 35% window Tint, Nitto Motivo Tires (6-8-18)
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