Went to drive across town to post office. Noticed speedometer not working. Then it started working. But. Only registered 30 mph at 2000 rpm in 5th gear. Came out of post office and it started working normally. On the way home it quit a couple of times then would work again. Sometimes normal other times low mph reading? Everything else works fine. I'm hoping it is the vehicle speed sensor. I noticed when I start up the needle came up to zero when working properly. When not it stayed "bottomed out". Has any one else experienced this? 2008 GT. 74,000 miles. Thanks.