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Discussion Starter · #22 ·
Indeed.

The other thing I noted is some sort of a grinding noise at cold that partly dissipates while warming up. When warm, it stays noticeable around 2000, or after a racing episode when the cvt gets back to the normal rpm.

I drove the car around yesterday and the racing issue only appears when trying to pick up speed starting between 5 to 20 mph at light throttle. In same conditions, the issue does not appear if I press the accelerator more frankly. No issue when starting from a standstill.

Back to the worn flow control valve and my idea of using thicker oil: I wasn't able to find kinematic viscosity info for the Nissan NS-2 fluid, but I was able to find it for other cvt fluids expressed in cSt or mm2/s which looks to be the same thing, at 40/100 degrees Celsius, and density expressed in g/ml at 15 degrees Celsius:

Valvoline: 34.5/7.2 and 0.854;
Castrol: 34/7.1 and 0.849;
Amsoil: 32.8/7.1and no info on density;
Beck Arnley: 29.93/7 and 0.85;
Idemitsu: 29.9/7 and 0.852

If I read this correctly Valvoline looks to be the most viscous one among the ones I picked. I am tempted to try a trans flush with it and see how it goes. I will save the Nissan NS-2 fluid which is new and put it back in in case it doesn't work well. This would be a stopgap measure anyway, waiting for a longer term solution while still being able to use the car.

Let me know what you think.
 

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If I read this correctly Valvoline looks to be the most viscous one among the ones I picked. I am tempted to try a trans flush with it and see how it goes. I will save the Nissan NS-2 fluid which is new and put it back in in case it doesn't work well. This would be a stopgap measure anyway, waiting for a longer term solution while still being able to use the car.
You can try it, but you have to keep in mind that this transmission had some inherent design flaws as alluded to earlier. Thus, given this fact and the age of the vehicle (despite the comparatively low mileage), you have to prepare for the possibility that there will be no "long-term" for this car.
 

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Discussion Starter · #24 ·
I just did two flushes with 6 quarts of Valvoline CVT fluid each time. So, fluid in the trans should now be about 75% Valvoline and 25% Nissan NS-2.

The rattling/grinding noise is almost completely gone. Transmission is running much smoother, though the racing issue as described above is still there, though not as bad.

So, it improved things, but didn't fully solve the issue.

I'm now trying to see if I can talk to a technician at Valvebodydepot (where I bought the valve body - sent a message asking for a phone number) and see if I can get some guidance on elements I could swap from the old valve body. The idea being that I have two different faults with two different valve bodies, so I should be able to make a good one out of the two.

If anybody has some ideas on what to swap, please let me know. As a reminder, I was getting code P0868 with the old valve body which hasn't returned nor the terrible jolting since I swapped the valve body. I am now getting code P1778 with engine racing symptom with the new valve body, which I wasn't getting with the old valve body.

Thanks
 

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Just my opinion and I've never rebuilt a valve body or a Nissan CVT, but I think taking parts from an old one and installing them on a new one is likely to complicate matters even more, because then you might not know 100% what's causing what to occur as a problem without again switching various parts, putting it all back together, testing it out, etc. I believe you're talking about taking old parts from an OEM VB and adding them to an aftermarket VB, and as I mentioned earlier, the tolerances/specs of both might not align perfectly, which could negatively affect the operation of the VB/CVT. Potential big can of worms, if you ask me. Not to mention you might void your warranty on the new VB, assuming it has one. Before I'd start swapping parts, I'd take a good look at the speed sensors and their connections and cleanliness, and I'd probably have a dealer do a reprogram of the TCM.

I never did end up replacing the primary or secondary speed sensors in my 2003, and that may be why towards the end I was getting "slack" acceleration when slowing and trying to reaccelerate. It's possible a speed sensor is preventing your CVT from variating correctly to align with what the torque converter and gas pedal or throttle body are doing. I describe "slack acceleration" as the car moving slightly more slowly than normal when depressing the gas pedal and the RPMs seem normal. It's not really lag/delay or sense of sluggishness...it just feels off a tad slow to respond perfectly. Of course, I had that 2003 since new, and drove it until April of this year, I noticed even subtle changes in everything it did.

BTW, are you getting any pending/inactive trouble codes for the CVT? I was always getting P0275 (or something like that, I don't recall) and they were always the last five inactive codes shown by the CVTz50 app. I'll try to find what the actual inactive code was and update if I can. Update...it was P0725 that pertained to a problem with the PCM.

Here's my old post about that code... Rear differential, transfer case, CVT filter/fluid...

Also, I'm not suggesting to do this, but I concluded that, for whatever reason, whenever I used straight NS-2 in the CVT, I'd throw P1778. Once I drained a quart and added Marvel Mystery Oil (MMO), the P1778s stopped and never returned...that is, until I drained the CVT and again added only NS-2. I did a comparison of both MMO and NS-2, and they were near-identical in appearance and viscosity to the eyes. I'm sure each fluid has different properties (I assume) that pertain to how they heat, cool, breakdown, etc. There again was a thread I read on the Altima forum (I think) where someone attributed their CVT being saved to using only MMO. I never got to that point because I ended up having engine issues before I got to try it, plus the CVT was improving just doing drains and more moderate experiments, so there was not point being overly aggressive.

Here's one of my pasts post about my use of MMO... Rear differential, transfer case, CVT filter/fluid...
 

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Discussion Starter · #26 ·
Thank you Cryogenix1.

Would you know where the primary and secondary speed sensors are on the transmission? I looked around it and couldn't find them. Unless they are inside?
 

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Input RPM is at about the 4 or 5 o'clock position looking from the engine side towards the transmission bellhousing. The speed sensor is hidden under the coolant piping on top of the transmission at about the 1 o clock position looking towards the engine. Careful with the one on top, there is in most cases a small shim washer under the sensor where the bolt goes through it. You will want to remove it first or else it could fall in the hole. Watch some youtube stuff on that subject before proceeding.
 

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As for the speed sensors, Chidog probably knows more than I do about this, but initially I mistakenly thought the secondary speed sensor was a redundancy or backup sensor in the event the primary sensor crapped out. Once I looked further into it, I realized that each performs its own task and works by itself to perform its part of the CVT functions. In my case, I threw a code related to the secondary speed sensor after doing an engine pressure wash, so I'm guessing I may have had a wiring problem to that sensor (an exposed area of wire, perhaps). With what you're describing as acceleration problems, it may point to a specific speed sensor, so maybe you don't have to bother fooling around with both. Again, maybe Chidog can be of help.

As Chidog mentioned, there's a spacer washer under the seat of the speed sensor housing that's used to create the proper distance from the sensor to the torque converter (or maybe it reads the flywheel...) Be sure not to damage or lose that spacer washer/shim if you take off the sensors.
 
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