Nissan CVT Transmissions: Coolers, Warranty, and Over-Cooling

• by VStar650CL
  
  For those of you who own a Nissan CVT-equipped vehicle, you’ve probably heard the horror stories about premature failures, warranty runarounds, and the massive expense of replacing one.
  
  Our Nissan Master Techs and factory engineers have provided some helpful information that should be ‘required reading’ if you’ve got a CVT-equipped car in the driveway.
  
  A CVT operates very differently than an automatic or manual transmission, which have actual mechanical gears, bathed in fluid, managing your engine’s output and transferring power to the driveshaft or drive axles at a predetermined ratio – a different numerical ratio for each gear. A CVT on the other hand, is basically comprised of a belt between two spindle-shaped spools. In order to keep the engine operating at maximum efficiency in its “sweet spot” of RPMs for a given load and throttle input, an infinite range of gear ratios is achieved by movement of that belt to wider or narrower locations on the spools during the driving process.
  
  
  
  Much like a conventional transmission, or even more so, heat is the absolute enemy of a CVT transmission. 176* is the widely-accepted “sweet spot” for optimal CVT operation. This presents a long list of challenges to a CVT-equipped vehicle: Pulling a long hill at full-throttle will send most 4-cylinder CVT fluid temperatures above 200* in no time. Towing a trailer puts particularly nasty shear stress on the CVT belt and fluid because of the back-and-forth inertia of the trailer, and with that comes excess heat. Add to this the strong likelihood that most people don’t regularly maintain their coolant (much less their CVT fluid), a radiator partially occluded with bugs and road debris, and vehicles loaded up with occupants and their supplies for a long trip, and you have a recipe for a roadside call for a flatbed and a hefty transmission replacement bill.
  
  For these reasons, a CVT fluid cooler is frankly the biggest favor you can do any CVT-equipped vehicle. Further, a properly-installed accessory cooler will not void the CVT warranty unless it can be proven to directly have contributed to a failure (leaking, clogging, etc).

However, there is an additional caveat: We don’t want to just slap a cooler in-line and call it a day. Over-cooling, especially for those living in climates with long periods of cold weather, can be just as problematic. Inexplicably, Nissan did not design their CVT transmissions with fluid thermostats, so even if the beehive and in-radiator cooler are left in place by way of series installation, the transmission may not be able to warm itself to proper operating temperature in brutally cold conditions.

The upshot of this is, part of a proper installation for warranty purposes will include adding a thermostatic bypass valve. After all, you wouldn’t want your engine operating at ambient air temperature for any appreciable length of time – that’s why you your cooling system is equipped with a thermostat, so that the engine can reach optimal operating temperature quickly – and remain there throughout your drive.

Functioning much like your thermostat, the bypass valve (also called H-Valves in the industry) works by recirculating flow back to the transmission until the fluid reaches a preset temperature, then allowing flow to reach the cooler, thereby maintaining fluid temperature in the aforementioned “sweet spot” around 180*. They use simple shuttle valves that are incredibly simple and reliable. There are two popular models made by Derale and Dana/Tru-Cool, both of which open at 180F and are available for about $50 on Amazon:

https://www.amazon.com/Derale-15719-Fluid-Control-Thermostat/dp/B004XONTNO
https://www.amazon.com/Tru-Cool-Long-Transmission-External-708-4739P6/dp/B008BTJFJ4

The 180F opening temperature is very near the ideal 176F “sweet spot” for CVT’s, so it should work fine for preserving both your CVT and your warranty. The Hayden 512 oil cooler is a popular choice for CVT owners, and it’s around $35.
https://www.amazon.com/Hayden-Automotive-512-Performance-Transmission/dp/B000C3DDEA

Even if your car is no longer under warranty, a $100 upgrade and a few hours for installation could mean the difference between a long-lasting, reliable vehicle long after your warranty expires, or an expensive paperweight with a premature CVT failure. Seems like a no-brainer to this guy. In fact, if you know someone else with a CVT, share this article with them – you’ll look like a hero, and maybe save them a ton of money!

As always, if you have questions, comments, or need assistance with your install, please feel free to pop in on the forums and ask away – Our knowledgeable and helpful members and staff are always ready to assist. Good luck, and we hope this is helpful.