Hi all! I am wondering if anyone knows what to look for that could be causing a strange vibration at 40 to 45 mph. As I was on my way home from work last night cruising down my road at 45 mph my 2003 G35 with 188k miles started shaking like crazy, didn't make any strange noises or anything, I got on the gas and as soon as the trans shifted up the problem went away. I'm worried it's a transmission issue but the trans wasn't slipping and it seemed to have no problem at all accelerating when I hit the gas. I bought this car 4 months ago and it had been sitting for about 6 months before I got it, I was having an issue with the oil cooler leaking and spraying onto the transmission connector just under the trans pan and that was causing it to go into transmission limp mode, but once I fixed that leak the problem disappeared, that was 2 months ago. I also replaced the trans filter, fluid and pan gasket just too be safe. I'm really trying to figure it out because I love this car, it's a blast to drive and it's my only car with a/c haha