Hi all, I've had a 6MT 2003 G35 coupe for about 14 years now and recently felt this strong shudder/shake when I accelerate in first gear from a full stop. It happens occasionally and only in first gear after a full stop. Has anyone dealt with this? I read around and some people are saying the rear differential bushing needed to be changed. My dad suggested getting my differential lubrication changed. I called infiniti and they said they never heard of this problem, which sounds like BS to me. They're also charging $200 just to take it for a test drive.

 

Shudder = slippage. Jack up the vehicle and look at the seam between the engine and transmission, is there fluid/oil accumulating like it's been dripping from that location? You may have blown a rear main seal which contaminated the clutch. If you're going down the highway in 5th/6th gear at about 2500 rpm and you floor it wide open throttle do you see the rpm's bounce up quickly but the car doesn't actually move that much faster?

Possibly not a contaminated but just a WORN clutch causing shudder as well, either way shudder is basically the clutch plate not engaging and sliding smoothly on the flywheel, something is causing differential friction and it can be a contaminated clutch or a glazed clutch usually. Do you ride the clutch a lot and possibly glazed it, particularly on higher rpm shifts with a lot of throttle.