Valve body diagnosis help

J

Jim165

Member
Location
Texas
Car
2014 QX70S
Hello all. 2014 QX70S 5.0 here. 146k miles with meticulous maintenance including 2 trans services at 60k snd 120k. So, I’ve just experienced the usual valve body failure….wont shift past 3rd, CEL, P0720 code. Took it to my Infiniti dealership and we couldn’t find an OEM VB anywhere. Our only choice was the unit from Nexenzo from eBay. Installed that with new fluid and they call me to tell me that the new fluid might’ve damaged the transmission. They are getting a 3rd gear fault. They claim the VB is working fine. I pick it up and it’s still not shifting to third, and poorly shifting from 1st to 2nd. However, this time there is no check engine light. I drove it 10 miles home in 2nd gear and the CEL never came on. D/S mode still doesn’t work nor the paddle shifters.
Question is, is the trans likely damaged as they say or is this rebuilt VB faulty as well? I’m assuming they’d program the VB if necessary at the dealership, but maybe not? Seeing conflicting info on if programming is necessary. Because this is the wife’s car, this fiasco has forced me to purchase another car since she needs immediate transportation. However, I’d hate to trash the QX if it’s just another bad VB. Problem is there are no OEM ones anywhere to be found. Already spent $2k at the dealership for them to not fix it. Maybe I take the loss and let it go?
 

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Did you get this figured out? The valve body controls the shifting, so to me it sounds like the TCM which is mounted to the valve body is not cooperating with your ECM and keeping it locked out ... although your engine is different, from what I've read the V8 models still use the same JATCO 7AT that every 370z, G37, M37, QX70 uses, so the valve bodies should be identical in design. When I bought my valve body from Arizona Infiniti Parts, they asked for my VIN and programmed it before shipping (or at least I think they did LOL). It worked right away. Their statement about the new fluid ruining yours trans makes no sense to me. I wouldn't trust them at all based on that statement alone.
 
LA_DRIVER said:
Did you get this figured out? The valve body controls the shifting, so to me it sounds like the TCM which is mounted to the valve body is not cooperating with your ECM and keeping it locked out ... although your engine is different, from what I've read the V8 models still use the same JATCO 7AT that every 370z, G37, M37, QX70 uses, so the valve bodies should be identical in design. When I bought my valve body from Arizona Infiniti Parts, they asked for my VIN and programmed it before shipping (or at least I think they did LOL). It worked right away. Their statement about the new fluid ruining yours trans makes no sense to me. I wouldn't trust them at all based on that statement alone.
Click to expand...
Hello LA_Driver, thanks for the reply! It’s still not fixed as of now. I have a guy that works on these cars and former Infiniti tech that will look at it but his schedule is a bit full for the next few weeks. Basically waiting on him. I agree with you, I really think the dealership made an error or missed some steps or something. From driving it, it seems there really could be a communication issue of some sort. I’ve read that these transmissions don’t really fail often at all, especially since I’ve serviced it regularly and it has never been beaten on (wife driven). As far as the use of a V6 valve body, the part numbers are not the same. I’ve read the trans are different from the V6s. The V8s use a beefier unit. I was hoping there was cross compatibility with the Armada/QX80/Titan but can’t find a cross reference. Might just have the guy throw one in from those 3 and see if it works.
 
Sorry to hear that! Yeah, I see how all the various valve bodies have different part #s - I just wonder what's truly different about them... when I got my used trans from a Japanese importer here in LA they said it didn't need programming at all! lol. I didn't believe that though, so I switched over my valve body and it worked perfectly. I did read that the V8 trans was beefier internally - I'd guess a stronger torque converter at least. I would imagine any Nissan/INFINITI where that engine was paired with that trans would be a perfect donor. I would try that for sure before giving up! There are a few places out here that import stuff from Japan, maybe they have a used one?
 
Yes, I think I will go the route of possibly using a VB from a QX80 if it’s reasonable. Luckily, we’ve replaced this car for the wife and this is now a project car with no rush to fix at this point. There are only 2 versions of this trans…the 710E good for up to like 295 ft lbs of torque and the 711E good to ~400 ft lbs. the 711E was used in the trucks and large SUVs as well as the 5.0 QX70/FX, so short of programming, there shouldn’t be a difference in VBs. Those VBs are readily available now as OEM. Now the question is whether I’ll spend another $1800 on a new VB or just buy a used trans and install since there still exists the possibility the trans is toast. Fingers crossed that it’s just a programming issue!
 
I am driving 2013 FX50S and I keep an eye on posts like this to be prepared for future potential scenarios with my own ride.
I just put your post into Gemini and here is the analysis, you might find it useful:




This is a classic, painful scenario for anyone running the heavy-hitting VK50VE 5.0L V8 platform (found in the rare FX50S and 2014 QX70S). These vehicles use the Jatco RE7R01A 7-speed automatic transmission, and the forum user is currently trapped between a dealership deflecting blame and a questionable aftermarket remanufactured part.

Here is a technical breakdown of what is actually happening in this post, why the dealership's explanation is highly suspicious, and what the user should do next.

1. The Dealership’s Claim is Nonsense​

The dealer's claim that "new fluid might’ve damaged the transmission" is almost certainly a cover story because they can't figure out why their $2,000 repair failed.

  • The Meticulous Maintenance Fact: The user stated the fluid was drained and filled at 60k and 120k miles. The old wives' tale about "new fluid destroying a transmission" usually applies only to severely neglected gearboxes where high friction material is suspended in burnt fluid keeping worn clutches from slipping.
  • The Reality: At 146k miles with that service history, the mechanical internals of this transmission are likely perfectly fine. The "3rd gear fault" they are seeing is a hydraulic or electronic control issue, not a sudden mechanical death caused by clean fluid.

2. The Programming Myth & The Real Culprit​

The core of this user's issue lies in the assembly they replaced. On the RE7R01A, the Transmission Control Module (TCM) is integrated directly onto the valve body itself inside the oil pan.




Here is why the car is acting completely erratic after the eBay swap:

  • The "Nexenzo" Element: Third-party eBay remanufacturers often replace only the obviously dead speed sensors or solenoids on a core, spray it clean, and ship it out. The mechanical valves inside the aluminum casting or the internal circuitry of the TCM itself could still be deeply flawed.
  • The Programming Issue: These TCMs store specific clutch calibration data (IP characteristics) and are hard-coded to the vehicle's VIN. If the dealership threw a pre-remanufactured unit into the car without performing a blank TCM write or successfully transferring/flashing the calibration files via Nissan/Infiniti CONSULT-III Plus, the transmission literally does not know how to accurately apply hydraulic pressure to shift into 3rd gear.
  • Why No CEL? The lack of a Check Engine Light (CEL) over a short 10-mile drive home is common. The generic OBD-II drive cycles take time to trigger a hard fault, or the aftermarket TCM is failing to broadcast the error correctly over the CAN bus network, which explains why D/S mode and the paddle shifters are completely dead—the car is operating in a deep electronic "limp mode."

What the Forum User Should Do Next​

If this were my vehicle, I would absolutely not trash a rare 5.0L QX70S over this. The physical gear train is likely robust. Instead of hunting for non-existent brand new OEM valve bodies, they should change their strategy entirely.

The Specialized Repair Path​

Instead of buying a generic swapped unit from eBay, the best route for an RE7R01A failure is sending their original, factory valve body out to a dedicated electronics repair facility (such as Circuit Board Medics or Xemodex). These services specifically rebuild the internal circuitry of your exact TCM and test the solenoids, meaning zero programming is required when it returns because it's already paired to the vehicle's VIN.

Recommended Action Plan​

  1. Demand the Original Part Back: The user needs to immediately call the dealership and demand their original factory valve body back before it gets tossed in the scrap bin.
  2. Get a Real Diagnostic Scan: They need a scan tool that reads proprietary Nissan transmission codes (not just generic OBD-II). They need to see if the current code is a communication error (U-code) or an incorrect component ratio/solenoid performance code.
  3. Bail on the Dealership: The dealer has clearly hit a wall and is guessing. The user should tow the vehicle to a highly rated, independent specialty transmission shop that understands modern, computer-controlled imports.
 
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