Hi all. Last autumn my "trans" went out while driving my g37x. I was accelerating past a semi when i could no longer accelerate. I finally got by and pulled to the side of the road. When I tried later to put in gear or reverse, no movement. Then a loud whining occurred, kinda like a ps pump but more intense. That happened only when the engine was on. So I'm thinking front trans pump, which means trans rebuild since I don't think I could tackle an auto trans myself. Way too expensive. Ended up purchasing a used trans as close spec to mine as possible. But started reading forums and watching videos about swapping issues, one issue that always popped up is tcm from non original trans would have to be reflashed. This would also cause the ecu to be reprogrammed according to a few who had theirs done. I really didn't want to lose my uprev license and after talking with my tuner about it, I decided to take a different approach. It seems the tcm gets coded the the original ecu at first engine start, and will only run properly if the 2 match. My notion, why not swap the tcm? I then found out that the tcm is actually mounted to the valvebody unit. No big deal right, just swap my original valvebody with the one inside the shipped trans. Well, my original vb was modified with transgo kit and thought it may have caused the trans problem to begin with. So wanted the vb from the shipped trans to be used. After looking at the removed vb from my original trans, i determined that the circuit board can removed.
Here are some photos of how this was done:

Remove the valvebody unit using the Nissan/Infiniti FSM. It has all the the bolt locations and their length to remove. It also explains the harness disconnecting. Notice the plastic covers.

Remove the covers by simply pulling up. They are not bolted on.
The black plastic is the tcm unit. It's held down by a few bolts and by all the solenoids that surround it. Almost every bolt is a M6 socket cap bolt with the exception of 2 M6 hex heads. Socket caps require 5mm allen, and hex head requires 10mm hex.

All solenoids are marked with an alpha-numeric code. Be sure to take a photo or list them on paper so as to re-install solenoids in proper location.

You can use a flat head to carefully pry up on the solenoids

They'll pop out and then slide out with a little resistance due to the o-rings.

Easy peasy

Once all removed, all that is left is a few bolts holding down the unit

There is a connector bracket that get in the way, just loosen bolt and move aside. But that is it. This unit can be put on any valvebody of choice. Just in reverse order.
Now, obviously, this needs to be done twice when swapping tcm to another valvebody. Then valvebody gets reinstalled to trans, trans fluid replaced, and should be good to go. I had NO startup issues when doing this. I did a test drive and it drove fine. Hope you find this useful

 

If you read the long introductory paragraph, and wondered about the noise, here is a follow-up. After the initial test, i drove my car the next day and it started leaking from the bellhousing quite steadily. After a lot trans removing and inspecting and testing, it was discovered that the shipped trans i installed, the torque converter was not set in correctly(my fault). Althogh splines were ok, the outer sleve was out of round and i put on original tc. The horrible squeel came back, so ultimately it was the tc that had failed and that was it. Inserts on shipped trans were also damaged. I decided to send my original tc to LevelTen for rebuild. Fortunately they were in stock so a few days later i got an update tc. Put it in the original trans, and swapped the tcm again into modified original vb. Also got LOJ kits flexplate, and reinstalled everything, then bolted trans in place. Put in Motul ATF VI. Works like it should, probably even better now.
some flexplate photos.

Stock flexplate

Very thin steel. May not be sturdy with increased horse power.

LOJ Kits VQ flexplate, much beefier billet aluminum, which keeps weight down

 

Special thank to my nephew for helping with project

5 years old and likes wrenching on cars.👍🏽

 

Well done!

 

First I've heard of the TCM programmed to the specific car. I'm running a Coupe trans in my sedan. Bolted in and have put about 20k miles on it. No reprogram, etc.

 

After I read the OP statement on this, I checked the FSM, and there is no mention of any "Special Actions" like when a new ECU is installed, plus with your experience, I suspect that info was incorrect.

 

Only special actions I've heard of are program updates for older cars in hopes of better shifting however Automatic G's get cursed with weird shifting and many have reached the consensus that it's a hardware/software issue specifically with the 7AT.

It's only a matter of time till Frank @MotorvateDIY gets himself an AUTO for research purposes.

 

I also searched the FSM, and I could not find it either. I really did this as a precautionary measure, as I've seen posts where they say they lost their tune when they reflashed tcm eeprom, and they reflashed because their "new" valve body was installed and there were driving issues. I dunno. At first, I called a few trans shops and none of them wanted to really work on it and all of them said that the valvebody needs retunedif is a new unit. Again, I dunno.

 

I have multiple Consult logs and when the TCM is updated, so is the ECU. I guess this assures everything is in alignment & synced.
From what I understand, a new TCM is blank and needs to be programmed as that would allow it to work with different versions of the G37 (options like ICC, etc) and probably other models like M37..

 

Do you mind telling us your review on the billet flex plate please

 

I've had what I believe to be a TCM issue for a while now. Do we know the earliest G37 with an updated TCM version stock? I'm considering going to a junk yard but I don't want to spend money on a TCM to find out it's not the right version and be in the same boat.

This is a great post by the way - definitely going to be my next project!

*side note* - I can't use the local dealership unfortunately. They updated the ECM without updating the TCM, screwed up my car, refused to fix it and aren't on the table as a solution unfortunately.