I have the 5-speed automatic in my 2008 G35x sedan. I find the transmission constantly shifts too early when accelerating and cuts off power from the engine, even with a lead foot. The automatic hits top (5th) gear at around 37 mph, and as a result the engine revs at 3,500 RPM when cruising at 75 mph. The shifts can also be really harsh, and sometimes there's a long hesitation between the 1-2 shift before it shifts into gear.

Is this a common issue with other G sedans? Is there a way to reset the transmission programming to fix these issues?

 

Start by cleaning up the ground wires, everything uses the chassis as a ground and if a single terminal starts to get a little corroded then it causes havoc on many systems and the transmission is DEFINITELY sensitive to it. Start with the two grounds on the front of the motor, then the larger gauge wire that's on the front passenger side engine, that one then goes down below the coolant reservior to the main chassis bond which has two bolts on it. You can simply unbolt the reservior and lift it up access that section. Next is the negative wire for the battery, the 2 bolt lug at the other end of the battery wire, and another jumper inside the same battery compartment. Finish up with the two at the front of the front tire wheel wells (one under power steering reservior and the other next to the MAF) and you have all the grounds checked in the engine compartment.

To clean each, remove the bolt, use a wire brush on the THREADS of the bolt and the shoulder below the bolt head, also brush the wire lug on both sides as well as the mating point on the chassis. No need to remove paint or anything the current flows through the threads of the fastener. Apply a thin layer of anti oxidation grease (DE-OX) to the threads of the bolt, both sides of the lug, and the chassis when reassembling. It takes very little de-ox to do this task so a little packet from an auto parts store will be plenty.

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