So I have an '06 G35 all stock besides it was lowered from previous owner. I was in a little accident a few months ago and am just now getting it back to driving condition. I had to replace the front crossmember, both control arms, and pretty much all of the drivers side suspension components. Not to mention, radiator and core support.

So the car drives great at low speeds, it's when I get above 40 mph that it has a faint pulsating vibration that I can feel it in the pedals and the floorboard. The vibration is very strange. It vibrates for a second and then stops for a second, then vibrates for a second and stops for a second, and so on.......And its not just a vibration, it's a very soft more like a pulsation of the pedals.

Now when I was in my accident my car caught some good air. There was dirt clogs all over the undercarriage, front to back. There are multiple little holes in my exhaust from it also, but that's not the issue. Just saying that with my exhaust being tore up like that I was thinking that it may be a drive shaft issue or left or right drive axle. Not sure if these are related but from a stop (occasional) it hesitates when I go to take off. I'm pretty sure the RPM's go up a bit but car doesn't go for a second. Then when it does there is a little "clunk" sound. Any help would be greatly appreciated from you guys, (and gals)

Welcome to the forum.
Wow, sounds like a bad crash.
So many things could have happened its hard to say where to begin.
Engine mounts, trans mount, exhaust touching the body, drive shafts, wheel bearings, bent wheel or hub, who knows.
For starters I would do a really thorough visual on everything, spin the wheels looking for wobble, and then drive the car on the lift and try to duplicate the sound, and use a stethoscope to listen to the drive train components.
Good luck

I replaced the engine mounts, tranny mount, and have new wheels and tires. My problem is I'm in a wheelchair and am relying on others to do the work for me. Never gets done right when you don't do it yourself. Lol. I'll keep at it. Gonna get at the drive shafts next. Thanks for the help.

Good luck