My 02 only has 64K miles on it and I think I have the valve body problem. What's happening is quite a lot of vibration in drive, and recently the car has begun to drop into what seems to be second gear and get stuck there. Like, I'll begin driving, get to maybe 40mph and suddenly the car downshifts, won't accelerate, too many RPM if I push on the accelerator. The last time it came with a lot of out-of-balance vibration, the kind of feeling you'd get with a RWD car if a universal joint failed on the prop shaft.
Can anyone tell me the type number for the valve body??? Is it an RE4F04A? There is nothing stamped on it. VQ35DE, not the 3.0L.

Although I do not have the experience to say or diagnose the problem you're describing, it most likely is the valve body because that is what tells the transmission to do what and when. I have a VQ35DE 02-03 maxima so the transmission code is RE4F04B. It can also be found near the engine code plate near the drivers side strut tower.

Wow what a helpful post, I'll check that tomorrow.
I am going to order a used VB from a tranny place in Austin, TX and I'll get the TransCo upgrade kit at the same time because this VB seems very prone to trouble. So, I'll install the upgrade kit in the used one and then get the shop to replace the faulty one with the upgrade.

^
The TransGo RE4F04B-HD2 is very nice but the 1-2 kick is a bit annoying

I'm just ordering the shift upgrade, not the hot-rod reprogramming!

PUR torque mounts REALLY help out with a VB mod. Without them, the shifts feel terribly clumsy.

Got a used valve body yesterday. Wow how complicated ... it's not just a matter of a type number. The guy pointed out that the bottom case has type letters stamped into it, like ZZ and AZ. Different oil pickup details I think. So this replacement came from elsewhere maybe a Quest or a XTrail or something... have to swop the bottom plate for my original (and clean it spotlessly in the process) - I am not getting into that, I am having the tranny shop do it. I know it's full of little springs and ***** and such. Argh!

Clive, have you pulled a code for all this? The valve body in your car is not so known to have problems as that in the 6th gen for example. And your car has just 64k miles. Why not run a scan and see what turns out. For all you know it just could be a camshaft or speed sensor issue.

I couldn't get any codes because the CAN was down. The shop later managed to get codes and told me that various tranny codes were shown but I haven't been able to ask them which ones as yet. I'm hoping to get it back on Monday. With luck.
- And, oh yeah, I just heard about the 6th gen. The tranny specialist started laughing when I mentioned that and said "you don't want one of those!"

My OEM VB was being stupid, replaced it at 39k, all is fine at 153k now, nearly 10 years later.

Where did you get the ValveBody Replacement? I might need one.

Did the 5.7th Gen Motor Swap and now the tranny is giving me a Solenoid code. I tried Car-part.com but they dont have an entry for Valvebody.

They’d rather not remove it so that's why they don't have it listed. Too much T&E. Not sure, but a VB mod usually won’t fix a solenoid code. A new solenoid pack will though. In any case, with the 09 Engine, you’re better off with the modified VB and Poly engine mounts, maybe even throw a torque link at it.

I have an extra stock VB lying in the garage. Not sure of maximum tuning still does this, might want to give them a call. They usually have some lying around too. Basically, you pay them IIRC 400$ with no core, and send them your core and they credit you 200$. That minimizes downtime for you, but you have to pay up front until you remove yours. And that's only if they have extra stockers lying around. If they don't, you have to send yours, they modify it, send it back and you;'re out a car until then, unless you want my stock unit.

Call them first to see if they even provide that service.

But then again there's always the TransGo kit as an added option too.

Picked the car up today and so far so good. Replaced front mount with aftermarket mount. Replaced valve body with one from a local tranny specialist - he was able to match the base plate code.

NOTE: The baseplate will have a code. I saw two: ZZ and AZ. And thinking it didn't matter, put on a different code (the VBs seemed identical.) And no reverse gear So it's good to know the type, like RE4FO4B or whatever, but you should also match the baseplate code.

So I am driving it around, so far so good, the mechanic told me to come back and pay him in a couple of days if all is good.

Apparently this sticking in second gear issue is pretty common and probably caused by dirt in the VB. It produced 700 codes, but not 720 (turbine). The oil in my car was really dirty, I don't think its first owner changed it EVER. Lack of maintenance. Using synthetic now.