Just had a meaningful chat with our Nissan TSM about add-on transmission coolers and warranty. I was surprised to hear that a properly-installed accessory cooler will not void the CVT warranty unless it directly contributes to a failure (leaking, clogging, etc). However, one direct contribution that isn't obvious would be over-cooling, especially for those living in climates with long periods of cold weather. Nissan CVT's don't have fluid thermostats, so even if the beehive and in-radiator cooler are left in place by way of series installation, the trans may not be able to warm itself in brutally cold conditions.

The upshot of this is, part of a proper installation for warranty purposes will be adding a thermostatic bypass valve. These are also called H-Valves in the industry, and work by recirculating flow back to the transmission until the fluid reaches a preset temperature, then allowing flow to reach the cooler. They use simple shuttle valves that are incredibly simple and reliable. There are two popular ones out there made by Derale and Dana/Tru-Cool, both of which open at 180F and are available for about $50 on eBay or Amazon:

https://www.ebay.com/itm/351915639948
https://www.ebay.com/itm/254865341453

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. I just ordered the Derale version for our Altima, which tends to run around 155F on the highway with a Hayden 512 cooler. It's no longer under warranty, but ideal is ideal. For $50 it seems like a no-brainer.

Interesting, but I question whether an add-on transmission cooler is even necessary? I could picture adding one if towing or with some other prolonged stressed usage (like a race track), but I don't see many CVT Altimas getting used that way.

Bubba1 wrote: ↑

Fri Jun 04, 2021 11:57 am

Interesting, but I question whether an add-on transmission cooler is even necessary? I could picture adding one if towing or with some other prolonged stressed usage (like a race track), but I don't see many CVT Altimas getting used that way.

Depends largely on how heavy your foot is and where you live. Ramming up a long hill at WOT will send most 4-cyl CVT's above 200F in no time flat.

Very interesting. I've always been curious about ways to prolong the life of a CVT since their issues were so widespread. I've always stayed far away from them for my personal vehicles, but mainly because I never totally trusted them and there wasn't anything I wanted bad enough that had one.

My father-in-law has a 2016 Pathfinder 4x4 that just sees regular use but he does plan to pull a small trailer from time to time, so this might not be a bad thing to consider for him.

Kompresshun wrote: ↑

Sat Jun 05, 2021 6:21 am

My father-in-law has a 2016 Pathfinder 4x4 that just sees regular use but he does plan to pull a small trailer from time to time, so this might not be a bad thing to consider for him.

A cooler is frankly the biggest favor you can do any CVT from any OEM, but trailering puts particularly nasty shear stress on the belt and fluid because of the back-and-forth inertia of the trailer. The Pathies have Schwarzenegger belts to be able to cope with it, but stress and heat are still inevitable. Tell your dad-in-law to keep the fluid fresh, and a cooler is definitely advised! I'd go with at least an 8-pass like a Hayden 1405.

VStar650CL wrote: ↑

Sat Jun 05, 2021 7:42 am

A cooler is frankly the biggest favor you can do any CVT from any OEM, but trailering puts particularly nasty shear stress on the belt and fluid because of the back-and-forth inertia of the trailer. The Pathies have Schwarzenegger belts to be able to cope with it, but stress and heat are still inevitable. Tell your dad-in-law to keep the fluid fresh, and a cooler is definitely advised! I'd go with at least an 8-pass like a Hayden 1405.

Good to know! I doubt he'll end up hauling a trailer with it, but he talks about it so I'd definitely rather do some preventative now while it's still under 100k miles.

I’d be hesitant myself living in northern Ohio. I noticed on brutally cold days my rogue cvt really struggles with the cold. Takes a good while to go through the fake shift points. Plus I’ve had my scanguage on my tranny, actually last week in 90 degree weather on the turnpike to Chicago and back and temps held steady around 175 which is well below the capabilities of the fluid. I’m still in the clean fluid=longevity camp with these turds.

D1dad wrote: ↑

Wed Jun 09, 2021 4:43 am

I’d be hesitant myself living in northern Ohio. I noticed on brutally cold days my rogue cvt really struggles with the cold. Takes a good while to go through the fake shift points. Plus I’ve had my scanguage on my tranny, actually last week in 90 degree weather on the turnpike to Chicago and back and temps held steady around 175 which is well below the capabilities of the fluid. I’m still in the clean fluid=longevity camp with these turds.

When I spoke with our TSM, his primary concern with coolers was over-cooling, since none of the Nissan CVT's have thermostatic valves. For a fairly flat ride like Ohio to Chicago, I wouldn't expect overheating to ever be an issue, so if that's your normal sort of drive, there's nothing wrong with adding an H-valve to the existing heat exchanger lines without adding a cooler. The primary source of warm-up heat is the beehive and not the radiator, so I'd expect cutting out the radiator when cold would greatly improve your cold weather warmup time without compromising the heat exchanger's ability to dump heat on the occasional steep hill.

As always, brilliant stuff from VStar... and now immortalized in a full-on homepage article.

AZhitman wrote: ↑

Sat Jul 03, 2021 10:14 pm

As always, brilliant stuff from VStar... and now immortalized in a full-on homepage article.

Just read it. Equally brilliant job of compilation and editing, AZ. Kudos to you!

You make it easy, amigo. Thanks for all you do for our peeps.

AZhitman wrote: ↑

Sun Jul 04, 2021 8:11 am

You make it easy, amigo. Thanks for all you do for our peeps.

Y'all make it a labor of love. You're most welcome always.

Was chatting with the DTS today and learned something interesting and helpful when installing a cooler on a Nissan. It's of course necessary to identify the outlet and return lines when installing an H-valve, because the valve won't operate with backwards flow. When installing a Derale H-valve on our Altima, I discovered (peculiarly) that the flow of CVT fluid through the radiator heat exchanger was bottom-up, not top-down like almost every other cooling device in the universe. I asked the DTS about this and his explanation, although counterintuitive, made perfect sense: Pushing the fluid bottom-up prevents any bubbles generated by the front pump from accumulating at the top of the heat exchanger and compromising its cooling ability, instead using their natural buoyancy to help sweep them out harmlessly into the return line.

The upshot is, it's easy to identify the outlet and inlet on any Nissan with a 4-port beehive and a side tank radiator. The bottom hose at the radiator is always the outlet, the upper is always the return.