My "new" 2006 G35x will hesitate/vibrate/shudder a little bit while in 5th gear on gentle upgrades and downgrades or when gently accelerating on a level road.

It feels like the car is in too high a gear and is struggling at too low an RPM. If I slap the shifter over into manual mode the transmission downshifts into 4th and the hesitation/vibration/shudder stops.

Also, the car will often upshift into 5th at very low speeds (around 30 mph).
Is that “normal” for this car?

 

There is an existing TSB for this which calls for the replacement of the valve body in the transmission. I had the same issue and had mine replaced at about 15k miles. ITB07-030 is the bulletin number. Since the VB replacement, I have had no issue and all had increased line pressure compared to the original. I cannot remember the increase off hand but I had it logged with auto enginuity.

 

Thx for the info sloppymax.