Hi,

I recently purchased a 2001 Infiniti G20 (base model, automatic transmission, 106000 miles). I've noticed that there is a vibration/shudder in the car during acceleration at speeds between 20-30mph. It feels like the shudder comes from underneath the gas pedal. Pretty smooth at other speeds and the steering wheel doen't shake either. Some shaking at speeds over 70. The shudder is less if I accelerate slower than normal, and more if accelerating quicker.

Transmission fluid is perfect in color, shifting seems very smooth.There is a soft 'clunk' going from P to R or D. But the clunk is almost gone when pressing the brakes harder. Most mechanics do not think it is tranmsission issue, except for one guy. I haven't noticed any abnormal rpm at any speeds.
Different mechanics in the last two months made me change passenger side control arm, driver side drive axle, do tire rotations, replace power steering hose, rear brakes and calipers, rear struts and all 4 motor mounts. Spent over $2500. The problem still persists. Any suggestions?

Out of 5 or 6 different shops I went to, one guy thought that my transmission might be going bad, but I doubt is since the shifting is so smooth and the fluid is perfect. I do have a knock sensor 1 Circuit (Bank 1 or Single Sensor) code stored when I checked last.

Thanks in advance!

Did you check the passenger side drive axle? A friend of mine had this same issue just last week on his acura and it was BOTH axles! lol

Thanks for your suggestion! I bought a ToughOneNew CV Axle Shaft Assembly , Part No NCV39520 from Advance Auto, and I will be taking the car to the mechanic next week for replacement. Most of the searches online did point me towards the axles being the culprit. I called a mechanic friend in Dallas who also suggested what you suggested. So I hope the problem will be fixed. The Firestone guy got me nervous when he blamed my transmission! I will update on the situation after replacement. And again, thanks for the input.

So I ended up changing the CV axle, after which for at least couple of hours, it all seemed smooth. Gradually vibrations came back, and eventually a day later, completely stalled on me on the road. Got it towed to the nearest garage, and discovered the CV joint had blown. So much for cheap brands. In any case, for those out there, keep away from the GSP brand CV axles from Advance Auto. There were warnings posted by other people about GSP brands axles which I saw after the fact unfortunately. In any case, these are listed as ToughOne New CV Axle Shaft Assembly at Advance Auto. It is possible the one I got was the bad one, but I think it pays to pay extra and get better ones. Cheers!

Good to hear you got it fixed! Bummer about the cheap brand giving you the run around!

I just bought a 2000 G20 recently and it has the identical shudder issue that you described. Did you get it completely fixed with the CV axle(s) replacement?