Hey guys. This is Saul Reisman, owner of Saul’s Autotek, and today I’m going to talk to you a little bit about CVT transmissions, constantly variable.
Now, most of the time, these transmissions operate in a way that allows a vehicle to accelerate quickly in one gear and then maintain speed without feeling that harsh shift that normal automatics exhibit. The downside of the design in most vehicles, like in this 2019 Nissan Pathfinder that we’re driving today, is that these are subject to serious overheat issues. There are bands inside the transmission that are submerged in a fluid that can create slippage when that fluid gets too hot. So today, it is currently 99 degrees. We’re in Hot Springs, Arkansas, it’s about 90% humidity, and we’re going up an 8% grade at 10 miles an hour in traffic. We’ve chosen this road that goes to the top of Hot Springs mountain as a great example of how this vehicle’s transmission will perform in extreme conditions and how it will fail.
The vehicle itself has 13,187 miles on it. It’s brand new. It’s only a year old. We’re going to go ahead and put this vehicle up this 10-mile drive, and then we’re going to take a temperature reading at the top. We’ll let you know how it goes. Stay tuned.
We’ve been going up this grade now for about 10 miles straight. We’ve been in it for just under 30 minutes. We’ve been in slow, congested traffic the whole time. We’re averaging about 20 miles an hour. At the start of it, the transmission temperature was approximately 120 degrees, according to the onboard computer. At this point, it’s currently indicating 202 degrees Fahrenheit. Now, we’re going to continue up this grade. We’re going to go ahead and let this transmission do what it’s designed to do, and we’re just going to see how hot it gets. The old rule of thumb from a mechanic is: A transmission at 150 degrees will last 250,000 miles and a transmission at 250 degrees will last 150 miles. We’ll report back. Stay tuned.
We’re still driving this 2019 Nissan Pathfinder and we’ve made it to the top and we’re just beginning our descent. We hit a maximum temperature of 248 degrees at the top of the hill, not exactly fantastic for the longevity of the transmission, and now as we’re making our descent, we realize we actually have a much different problem being that we’re in congestion and going down a steep grade at low speeds, the transmission does have time to cool off. However, because the vehicle doesn’t actually have physical gears to lockout for its low range as you would in a typical automatic or manual transmission vehicle, we’re actually currently in the lowest gear the vehicle has to offer. It’s indicating it’s all the way in the lowest range. However, because that gear doesn’t actually have a ratio against it, there’s no compression breaking that actually happens from the engine. As a result, as we go down this hill, we have no choice but to hit the brakes into almost every corner, and you use the brake pedal to maintain vehicle speed.
Your brakes are designed to stop the vehicle, your gas pedal is designed to accelerate or maintain that speed, and the gears are designed to control that speed. If you don’t have any gears, like in this CVT transmission in this Nissan Pathfinder, you can’t safely control your speed while making a descent. Luckily, the descent that we’re making today is only about a 2,000-foot vertical drop. However, if you are driving this vehicle from, say, the Eisenhower tunnel on I-70 down to Denver and making the 6,000-foot vertical drop over 44 miles, you would more than likely overheat the brakes of the vehicle, glaze them, warp the rotors, or cause even more serious damage to them. It could even damage the caliper, all because that CVT transmission doesn’t give you an option to physically slow the vehicle down. As a result, here we are heating up the brakes, going down a mountain. We’ll talk to you soon. Stay tuned.
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