Hybrid CVT Jatco JF018EMaxim Golikov
Transmission repair specialist. Agregatka, Kazan.
There are design differences in the planetary gearbox - the sun gear is part of the input shaft, and the crown gear is connected to the cone. For the JF017E model, the opposite is true. The speed sensor in the JF017E model is located on the drum, and in the JF018E model it is located on the electric motor.The transmission has been in production since 2012, and quite a few cars equipped with it have come to the age when they need repairs. This CVT is installed on versions with a hybrid drive - Nissan X-Trail, Nissan Pathfinder and Infiniti QX60. In Russia, the Pathfinder Hybrid was assembled at a plant in St. Petersburg, but not for long, so they are not so common. Such cars are imported into our country used. They were delivered to Kazan several times already, and there I got acquainted with this transmission.
Why do we need a hybrid?
The hybrid drive saves fuel by conserving some of the energy that is normally wasted - for example, when decelerating or coasting - by storing it in a battery and then releasing it when needed. Hybrids have the ability to drive only electric, but in this case, fuel is not consumed and there is no exhaust gas,
but the power of the electric motor is small, only 15 kW (a little over 20 hp), and the battery of the hybrid drive is not very capacious. This is commonly referred to as a mild hybrid. The main purpose of the hybrid drive is the "Start-Stop" system: when stopping at a traffic light, the ICE is turned off so as not to waste fuel, and then the car starts off on the electric drive and the ICE starts on the move. The electric motor reaches its maximum torque at minimum speed (in this case 160 Nm), and this is very convenient for starting off. As a result, both fuel consumption (according to official data, by 15-20%) and carbon dioxide emissions are reduced, and in many countries this parameter is important for calculating car taxes. The electric motor also helps the ICE during intensive acceleration, so that a car with a 2.5 l/230 hp four-cylinder petrol engine has dynamic characteristics not worse than the model with V6 3.5 l/250 hp and at the same time consumes less fuel, especially in conditions of frequent acceleration and deceleration.
Гибридный привод обеспечивает снижение расхода топлива благодаря тому, что может сберегать часть обычно теряющейся энергии, например, при замедлении или движении накатом, запасая ее в аккумуляторе и затем при необходимости отдавая. Гибриды могут двигаться только на электроприводе, в этом случае топливо не расходуется и отработавших газов нет.
Но мощность электромотора невелика, всего 15 кВт (чуть больше 20 л.с.), и батарея гибридного привода не очень емкая. Это обычно называют «мягким», или «умеренным» гибридом (по-английски mild hybrid). Основное назначение гибридного привода – система «Старт-стоп», когда на светофоре ДВС выключают, чтобы не тратить топливо, а затем машина трогается на электроприводе и ДВС запускается на ходу. Электромотор на минимальных оборотах развивает максимальный крутящий момент (в данном случае 160 Нм), и это очень удобно для трогания. В итоге снижается и расход топлива (по официальным данным, на 15–20%), и выбросы углекислого газа, а во многих странах именно по этому параметру рассчитывают налоги на автомобили. Электромотор также помогает ДВС при интенсивном разгоне, так что машина с бензиновой «четверкой» 2,5 л/230 л.с. имеет динамические характеристики не хуже, чем модель с V6 3,5 л/250 л.с. При этом расходует меньше топлива. Особенно в условиях частых разгонов и торможений.
Motor instead of transformer
The transmission is the main assembly of the hybrid drive. The JF018E model is based on the popular JF017E chain continuously variable transmission, which is part of the Jatco CVT8 range. Its main difference is that an electric motor takes the place of the torque converter. In order to ensure the switching of the hybrid drive modes, the CVT has a dry multiple-disc clutch, through which the electric motor is connected to the gasoline engine, and a wet clutch, which connects (or disconnects) the electric motor to the main pulleys.
The electric motor also acts as a generator.
If the first clutch is open and the second is closed, then the drive becomes fully electric - this is what happens when starting off. If the electric motor is disconnected from the actual variable transmission, but connected to the engine, it is possible to recharge the traction battery while the vehicle is stationary. And with both clutches closed, the car runs on a gasoline engine and can recharge the battery when the car slows down. The switching of the clutches and the operating mode of the electric vehicle is performed by the control system.
What’s the difference?
There are design differences in the planetary gearbox - the sun gear is part of the input shaft, and the crown gear is connected to the cone. For the JF017E model, the opposite is true. The speed sensor in the JF017E model is located on the drum, and in the JF018E model it is located on the electric motor.
Due to these differences, the clutches of the Forward configuration are not interchangeable. In the Reverse configuration, the steel discs are the same, but the clutches are different.
The valve bodies of the two transmissions are very similar in appearance, but inside they are different, and they also cannot be replaced with one another. So, in the JF018E plate there are no channels for controlling the torque converter lockup. The valves are also different - in particular, their springs. The JF018E separator plate has additional holes.
The lockup control solenoid in the JF017E is normally-open, and in the JF018E the clutch control solenoid is normally-closed, so the clutch will also work in emergency mode.
This must be taken into account during repairs and only appropriate spare parts must be used.
Due to the fact that the car engine does not run constantly, an electrically driven pump is provided in the JF18E to maintain the operating fluid pressure, in particular for lubricating and cooling the wet clutch. It is a three-phase synchronous brushless motor controlled by the Transmission Control Module.
It's worth noting that overheating is an inherent problem in the hybrid, and Pathfinder even has a warning light on the instrument panel. If this message appears, the car stops. To cool the transmission, the engine has an antifreeze circuit and a radiator. But it's located under the front fender and clogs up pretty quickly. It is recommended to clean it at least once a year.
Typical CVT problems are the same as with conventional transmissions of this type. And in 80% of cases, we did not have to repair the hybrid part. The troubleshooting methods are the same.
However, there are specific malfunctions that appear precisely on the hybrid drive.
On one car with a mileage of about 80 thousand km, after starting off on an electric drive, when the ICE was turned on, a noticeable blow was felt. Having disassembled the transmission, we determined that the clutches in the dry clutch package were washed out, the steel discs were polished, and a lot of wear products had accumulated in the drum. This prevented the clutch from working properly. The clutch was beyond repair and had to be replaced. After that, we made an adaptation.
There may also be problems with the electric oil pump, as valve malfunctions occur. Only the valve can be replaced, but it is important to reset errors. Sometimes the pump itself wears out: we got a car that had problems with starting, and the reason was just a worn pump. After replacing the pump, everything returned to normal.
Original is better
For diagnostic purposes, it is better to use dealer equipment - Nissan Consult III Plus tester. We have used a lot of multibrand scanners, they really allow you to reset error codes from this transmission, but sometimes their capabilities are not enough. And an original scanner allows for adaptation after repair and recording new calibrations. We came across cars that had all calibrations reset during the "garage" repair. This can be done accidentally, and then the electronic control module will not work with the transmission. Therefore, we always save the calibrations. TCM memory accumulates data during operation, and if we replace parts during repairs, it is better to delete intermediate data, but calibrations must be left.
We do not have a complete database of calibrations, so we take the desired option from the available ones. We are not able to create new calibrations, but we select solenoids corresponding to the existing calibrations.
We have not yet had to replace the valve bodies - these transmissions are still quite new. On the other hand, the solenoids were replaced quite often: if after checking the solenoid at the stand we see that its parameters are out of range and flushing no longer helps, it must be changed. New valve bodies are supplied with a disc for loading new calibrations. But they only work with a new valve body. After repair and replacement of solenoids, new calibrations must be registered.
In Russia, hybrid Nissan Pathfinder was produced from 2014 to 2017, and they are already approaching the age when they need repairs. Experience shows that the valve bodies most likely have to be repaired or changed when the mileage is over 100 thousand km. Therefore, in the near future, customers with this type of CVT will come to you more often.