What is the correct Transmission for my G35
 

Hello all
I just acquired a 2003 G35 Sedan from family member. it is getting several codes according to shop. Inoticed car does not go faster then 40MPH. Doesnt seem to shift into overdrive. Shop says it has a slip as well. I looked up trannys for it and found the sites asked me what year car was manufactered. Giving me the impression that the 2003 has several different transmission for it. After talking to my nephew he said he had a 2004 engine put in it. The repair shop said that transmission that is in it is fine with that motor. It did work find for a couple of weeks then this issue started. My question is does the 03 use different transmission for the same year? Now this car has a 2004 engine. How do I make sure I get the correct tranny for it. I asked others and they say it uses the same tranny for the 03 and 04. If so why do the tranny place ask for manu date of car. If it does not then how do I find the correct one for a 2004 engine? I do nto know when that engine vehicle was manufactered. Confused yet? I am. Need to know do 2003 use several different trannys in it and if 2004 does also. How do I know what tranny is right for my car.
Thank YOu so much
dacrew4009
2003 Infiniti G35 Sedan Automatic (with 2004 engine in it)

The engine was the same for 2003-2004. The transmission was changed halfway through 2004 and they relocated the TCM to an internally mounted design rather than it being next to the ECU in the cabin. You can tell the transmissions apart because the older one (that you probably need) has a wiring harness with 3 green plugs and a short pigtail of wire coming out of the transmission. The newer style has a large grey single electrical harness mounted in the grommet of the transmission instead.

They want the manufacturer date because it's a $2500 item they need to order and there were like a dozen revisions across the life of the G35 and even though they basically broke down into 2 major revisions they want to give you the 100% exact transmission (even though a bunch of revisions are all completely compatible with each other).

It's also possible to keep the TCM and valve body from the existing transmission and use ANY G35 5AT transmission but it requires someone who knows how to swap those components over. You could even take the transmission from an AWD and unbolt the transfer case, use the existing tail housing from your transmission as well as the valve body and TCM. There's a lot of options if you know how to work on transmissions. Otherwise the vendor is going to sell you THE EXACT ONE installed in your vehicle.

Correct Tranny for 03 G35
 

I looked so long for this answer. No one could give me a true complete answer. I want to thank you Cleric670 for your help and for sharing your knowledge. My car has a Manufactured date of 02/02 so now I know I need a tranny with a date of 03/02 or before. I was just not sure since it had a 04 engine and many transmissions for the model year. I will start my hunt for a 03/02 or before transmission.
AGAIN, Thank You
dacrew4009
Do you know of a site that gives a play by play on replacing Tranny? Does the Hanes or Chilton book give a step by step on replacing this transmission?
Thanks

Hey Cleric670
I have one more question hoping you could answer it. I noticed in your reply you mentioned certain trannys may need to swap components over. If I were to use to buy a tranny from same manufactured date then all I would need to do is swap trannys correct. Not swap computers.???