I am not a car guy, so pls forgive some of my verbage. I have a G35 Sedan, the first 2003A model. It has 131k miles on it. Sometime around Oct of 2008, the car started to shake when driving. It did not matter the speed, or anything. At first it was very subtle, as if I hit brake by mistake. Then the car cut off twice @ stop lights. As time went on, I took it to the dealer for something else (power seat problem) and asked them to check it out. Dealer was so swamped they never looked at it. I then got a new job, got a company car and didnt drive mine much. I started driving it again, and same problem. Driving say on freeway, at 60-70, violent shakes. Does not cut off, then it will stop.

No check engine light, nada. Took it to a mechanic and have a spark plug change, and transmission flush. Mechanic drove it and said no shaking. I drove it @ first, no shake. Soon after shake and check engine light comes on. Back to mechanic, and error code says that gas cap is lose. Once this is tighten and cap tightened and light went off. Start driving again, and subtle shaking. Got oil change, no change. Upon getting oil change, got a quote from NTB for Rack & Pinion replacement, along with alignment, PS flush, alt belt and PS belt.

I call mechanic, he says bring back but NTB is known for saying this regardless if this is the issue or not. Upon driving it today, I then get again a violent series of shakes, and now check engine light is on, and slip light came on, and also a VOD (sp?) light came on. Stopped, ran errand, turned car back on, and only check engine light is on.

But I am not sure if I will ever get an idea of what is causing this, so looking for an ideas that might be it. Would the Rack & Pinion cause this? I saw the note upon a search about a transmission recall and shake at 40 MPH on different model cars. Not sure if this is the same, as I think that was 05-06 cars...

Any advice??

Thanks!