Hello fellow Versa owners. I've been researching some problems I've been having on my 115k mile Note and this forum came up in my Google searches with helpful info.

So $400 later, my surging and slipping CVT is back to normal, but, I am now armed with knowledge and CVTz50. Here are my questions:

1. Since the CVT temp seems to track within 5 degrees C of the engine temp under highway conditions, could the engine temp be lowered by 5 degrees C to help the CVT stay a little cooler? This would require a custom thermostat but it seems easy enough.

2. How much does a trans oil cooler help to lower cvt temps? I have a 30 min highway commute and I notice that I'll hit 90 degrees C after about 20-25 mins of driving. Would it buy me more time, but also prevent the cvt from ever hitting 90? Just skeptical of the flow volume through that stock cooler block.

3. Does anyone know the fluid deterioration replacement value for my Note? I notice I get around +15 to +20 deterioration per commute if I'm cruising 75-80 mph. Just wondering if that's a normal burn rate on new fluid.

Thanks for your time,
Ted

1. Not a good idea. It will definitely increase engine wear and may cause the ECM to throw a code.

2. I should preface this by noting that none of the 2-speed Versa/Sentra CVT's have OE heat exchangers, they all have 2-port beehives. That makes them exceptionally vulnerable to overheated fluid. Without a bypass (H-valve), even a small radiating cooler will drop the temp substantially. How much depends a lot on the cooler. With a 180F H-valve, the temp will steady out around 185F (85C) and won't go much higher. Because trannies experience accelerated mechanical wear at low temps just like engines, an H-valve is a good idea if you live in a climate with any sort of real winter. H-valves can be internal or external to the cooler, Dana-TruCool makes some very nice ones with an H built-in.

3. Since thermal deterioration only matters above 90C, any good cooler will basically reduce it to zero. However, the other factor in deterioration (which the TCM can't measure) is mechanical shear force, which gradually breaks down the long-chain molecules in the fluid. For that reason, 30K fluid changes should be the rule regardless of temperature and you should forget the deterioration value for appraising your fluid quality. Shorter intervals are called for if you have a lead foot, drive in a steep area, or pull any trailer regardless of weight.

VStar650CL wrote: ↑

Tue Nov 02, 2021 5:40 pm

1. Not a good idea. It will definitely increase engine wear and may cause the ECM to throw a code.

Understood. I guess this also exposes the problem with the beehive.

VStar650CL wrote: ↑

Tue Nov 02, 2021 5:40 pm

2. I should preface this by noting that none of the 2-speed Versa/Sentra CVT's have OE heat exchangers, they all have 2-port beehives. That makes them exceptionally vulnerable to overheated fluid. Without a bypass (H-valve), even a small radiating cooler will drop the temp substantially. How much depends a lot on the cooler. With a 180F H-valve, the temp will steady out around 185F (85C) and won't go much higher. Because trannies experience accelerated mechanical wear at low temps just like engines, an H-valve is a good idea if you live in a climate with any sort of real winter. H-valves can be internal or external to the cooler, Dana-TruCool makes some very nice ones with an H built-in.

Thanks. I will research the H valve and make sure it's part of any cooler upgrade.

VStar650CL wrote: ↑

Tue Nov 02, 2021 5:40 pm

3. Since thermal deterioration only matters above 90C, any good cooler will basically reduce it to zero. However, the other factor in deterioration (which the TCM can't measure) is mechanical shear force, which gradually breaks down the long-chain molecules in the fluid. For that reason, 30K fluid changes should be the rule regardless of temperature and you should forget the deterioration value for appraising your fluid quality. Shorter intervals are called for if you have a lead foot, drive in a steep area, or pull any trailer regardless of weight.

I guess I left out an important detail which is that I live in FL, so very little elevation but heat is a big problem. Makes sense about the mechanical wear, though. I was wondering if their deterioration equation looks at HP or slip or other factors like that.

tedsar wrote: ↑

Tue Nov 02, 2021 7:20 pm

I guess I left out an important detail which is that I live in FL, so very little elevation but heat is a big problem. Makes sense about the mechanical wear, though. I was wondering if their deterioration equation looks at HP or slip or other factors like that.

Nope, it's purely looking for time-at-temperature. Mechanical wear only becomes an issue at temps below 120F or so, and in Florida that won't be a factor. Do get a cooler though. Plain-jane should be fine in that climate, no H needed (although you'll still need a retrofit 4-port beehive along with the cooler kit).

Looks like I already have the 4 port, so just need to add oil cooler and call it done?

Yep. I'm surprised you're running that warm if your car already has an exchanger in the radiator, most of them run 150~170F on the highway if the cooling system is healthy. I was under the impression that even the late model 2-speeds had only 2-port hives, but I guess there must be exceptions. There is a Nissan cooler kit available, so see where the fluid hoses from the beehive go. If they go to the radiator outlet tank, then it's a heat exchanger and you can tack on a cooler. If they go to a radiating cooler then it's a retrofit kit installation and something must be the matter.

I've been running controlled tests on the cvt during my commutes where I set cruise to different speeds each time. I've discovered that in this mild weather, 72mph max will ensure no overheating (at least for 30mins). This is painful since the speed limit is 70, and most of traffic is cruising 75-80. Anyway, I've ordered the cooler and will give an update on its performance.

tedsar wrote: ↑

Tue Nov 09, 2021 9:11 pm

I've discovered that in this mild weather, 72mph max will ensure no overheating (at least for 30mins). This is painful since the speed limit is 70, and most of traffic is cruising 75-80. Anyway, I've ordered the cooler and will give an update on its performance.

That isn't normal for a car with an exchanger. While you have the hoses loose to install the cooler, get a can of CVT flusher from the dealer and flush out the heat exchanger and hoses. The cooler will be in series with the exchanger, so if there's a clog the cooler will have little or no benefit. Make sure everything is clear.

VStar650CL wrote: ↑

Wed Nov 10, 2021 5:44 am

tedsar wrote: ↑

Tue Nov 09, 2021 9:11 pm

I've discovered that in this mild weather, 72mph max will ensure no overheating (at least for 30mins). This is painful since the speed limit is 70, and most of traffic is cruising 75-80. Anyway, I've ordered the cooler and will give an update on its performance.

That isn't normal for a car with an exchanger. While you have the hoses loose to install the cooler, get a can of CVT flusher from the dealer and flush out the heat exchanger and hoses. The cooler will be in series with the exchanger, so if there's a clog the cooler will have little or no benefit. Make sure everything is clear.

That makes sense. Would it be better to bypass the exchanger completely? There would still be coolant lines running into the beehive.

No, heat transfer between liquids is on average 27 times more efficient than to air, so when the exchanger works right it's extremely effective. That's why I was surprised your temps are running so high on the highway. However, the exchanger relies on the engine's cooling system, so there are circumstances where it could become ineffective. One is very heavy engine loading that pushes the cooling system to its limits (say, climbing a mountainside on a hot day), another is if your cooling system has a problem that blocks or reduces coolant flow (say, a stuck thermostat). Under those conditions, the exchanger can't do its job and a radiating cooler will save your tranny.

One other thing you might check is the beehive thermostat. It happens that I had this exact same issue and posted about it. The coolant lines to the hive come from the heater circuit and not the main loop, and they have an embedded thermostat that works in reverse from a normal one. That's because its purpose is to allow the tranny to warm up quickly, not cool it off. If the 'stat sticks open it will dump hot coolant constantly into the hive even when the tranny is already warm. On our Altie it caused almost a 20F difference in cruising temperature. Unfortunately there's no great way to test them without pulling them out, so I just replaced both beehive hoses on ours and the 'stat with it. But the temp gauge confirmed that the old one was malfunctioning, there was a noticeable drop in overall fluid temperature.

Dang. Yeah I'll have to check that too while I'm putting in the cooler.

Sorry for the late reply, but I finally got the auxiliary trans cooler installed yesterday, and it works! Wasn't able to get it over 185 F on highway test (85 mph) run and normal commute (75mph/176 F). I also didn't encounter a thermostat, only 4 molded hoses from the beehive. I tried to force some NS-3 into the beehive hose before clamping the last hose, but I think I'm still a bit low on fluid, so my next task is to take out overflow plug with the car idling, and fill it till it leaks?

Put in about half a quart more than you think it needs and warm it up, then pull the plug. Let it drain until the stream "hiccups" (we've found that letting them drain all the way till they stop leaves them slightly low). Reinstall the plug and you're good to go. That's more reliable than topping it till fluid comes out, because you're pre-voiding any air that might be in the passages from being low.

PS - If I remember right (and maybe I don't), the CVT 'stat on a Versa should be on top of the tranny where the outlet from the thermostat T's to the heater core and the CVT. Most of them look like a tee or a union. Some are part of the hose assembly and can't be bought separately, but I don't think that's true on a Versa or Note.

Good call. Since my CVT is one of the "cool" ones, I don't have a dipstick. I'm hoping I can fill it through the plug on the side of the CVT, just above the pan.

There should definitely be a charge pipe, just no dipstick in it. It isn't obvious on a Versa or Note because it's short and buried all the way in the front left corner of the tranny.

VStar650CL wrote: ↑

Tue Jan 18, 2022 5:44 pm

There should definitely be a charge pipe, just no dipstick in it. It isn't obvious on a Versa or Note because it's short and buried all the way in the front left corner of the tranny.

You were right, again. I wasn't looking hard enough. I got the extra half-quart in there and will see tomorrow if it's acting better. Hopefully this is the end of my CVT saga.

In total I added just under 1 qt of NS-3, and it's driving much better than it was right after the cooler install. I must have lost more fluid than it appeared. I am still getting some surging during acceleration at lower RPMs, so I don't know if that points to a clogged pickup screen or something worse . I've only replaced the paper filter and the pan has never been dropped (120k miles).

CVT's have very little clutch material (even the 2-speed ones like yours), so they never make "ATF soup" like a conventional A/T. If your screen is clogged then it will be the first one I ever saw. Since you have CVTz50, look at the input speed, output speed and target ratio when it misbehaves. If the input speed isn't following the target ratio and "jumps" relative to the output speed, then the belt is slipping.