My 2013 rwd g37 (112,000 miles) recently got the check engine light. i noticed something was up this morning when i felt a subtle jerk when idling. later in the day my car began shifting late, at about 4k rpms, struggling to reach 2nd and 3rd. And not being able to go into sport or manual mode. I frantically drove to autozone which they found the code P0720 came up.

So now I have been searching on marketplace for a used valve body from a similar car to mine since i know that you cannot interchange them with q50 valve bodies and things of that nature.

My overall question here that i am trying to get to is can i put a valve body from a 2011 AWD g37 into my 2013 RWD g37?? is this okay? I am fairly new with anything transmission related and i’m scared to be out on 500 dollars with a messed up car and no fix! On the infiniti site it’s saying it doesn’t fit but maybe i am looking wrong?! Hopefully one of you guys have the answer im looking for.

Please if anyone can help that’ll be greatly appreciated. This guy on marketplace is insisting that his Valve body fits in my car with no issues but i fear i’m just collecting another man’s trash and it will cause no benefits towards my issues i’m experiencing.

(EDIT): I am going to do a transmission flush tomorrow morning to see if maybe that’ll do anything at all (got the car 4000 miles ago at 108,000, idk if it has been flushed yet but i am guessing not.)

 

P0720 could mean several things. Could be as simple as your output speed sensor is faulty and needs to be replaced. Could be something much more time consuming to repair, such as 1 or more of the clutch packs are slipping excessively. There is the possibility that your transmission fluid is dirty and is blocking flow in the valve body. The transmission fluid change is a good place to start. If that doesn’t solve the issue I suggest making sure you absolutely know that the issue is the valve body before replacing it. It may just end up being a waste of your time and effort.

As far as I know there is no difference between the AWD and RWD valve body. Only that you will need to swap your TCM from your old valve body to the new one. Unless you get the new one reprogrammed to your ECU. The Q50 valve body will fit in your transmission but you must use your old TCM. The VR30 Q50 TCM cannot be reprogrammed for a VQ37 ECU.

If you determine that the issues are related to the clutches, gear sets, torque converter… really anything that would require a rebuild, then look into doing a VR30 transmission swap. Lots of low mileage VR30 Q50 transmissions for cheap on eBay. If you DIY, don’t go overboard, and know how to do basic fabrication you can have the updated transmission swapped in for under $1.5k.

 

Would i have to re program a used valve body with a used tcm?

 

No. The valve body is just hardware. All of the electronics are housed on the TCM, which is bolted directly onto the valve body. When swapping out the valve body you would move your TCM to the new valve body. If the TCM itself needs to be replaced then you would need to have it programmed.

 

Anh okay, makes sense. So with my issue only being the code P0720, what if i buy a valve body from the same make model and year as my car, would i then be able to swap both the valve body and the new tcm without programming? or is it just best to buy the valve body and bolt on my old tcm to it? sorry im new to this, i really appreciate the help man seriously!

 

as far as I know you would still need to have the new TCM programmed since it is tied to the VIN info on the ECU. You will not have to reprogram anything so long as you continue using your current TCM. Most people probably are not going to sell you a valve body and TCM separately.

Red is the TCM. Green are the solenoids. Blue is the valve body itself.

Hopefully this helps. To reiterate though, are you sure that the issues you’re having are being caused by the valve body? With the mileage on your car it’s not uncommon for things like the torque converter, clutches, etc to start failing. Especially if the previous owner drove it hard and listened to Infiniti and never changed the fluid. Just trying to save you the headache.

 

I just got it looked at, the mechanic said the speed sensor is bad and he could quote me on an entirely new transmission, or i can take the chance with swapping the valve body. I personally don’t know if it is anything to do with the clutches or other moving parts in the transmission. I think the first thing i will try to do is swap the valve body, if that does not work i will return it for a vr30 transmission that would last me longer.

The whole hesitation on not just getting the transmission is due to financial struggles, im a college student who isn’t working right now due to health issues, but im just trying to keep my g running good the most cost efficient way. i love the car so im trying to get it in good shape.

 

Just being the speed sensor is good news. I'm not sure why the mechanic would be quoting you on an entirely new transmission if they are confident in their diagnosis. An OEM speed sensor will run you about $160 (part number 31935-1XJ0D). It's not a very difficult DIY replacement, but paying an extra $100-200 for labor might be good insurance if the new sensor is DOA. If you decide to DIY you will need to remove the valve body to remove the sensor, but I still don't think it's necessary to replace it. A better use of your time would be removing the solenoids from the TCM and checking their electrical resistance. I attached the transmission section from the FSM. Pg. 168 is information about your specific DTC.

 

You might want to read this post and the thread in general.

The problem with the P0720 is that the issue almost always lies in the electronics of the TCM. The actual sensor almost never fails. Also, due to the work involved just to get to the sensor, most opt to just replace the TCM and call it a day. Even Infiniti advised the same procedure for the Q's.