Valve body diagnosis help

[Jim165]

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?

 

[LA_DRIVER]

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.

 

[Jim165]

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.

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.

 

[LA_DRIVER]

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?

 

[Jim165]

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!