RAV4 EV Motor Repair

Toyota RAV4 EV Drive Unit/Motor Repair

The Rav4 EV is an electric car sold by Toyota from 2012 to 2014. It was only sold in California and a total of 2,600 units were produced. Unlike the first generation RAV4 EV from the 90’s the second-generation EV used a powertrain sourced from Tesla Motors. This includes the motor/inverter, the battery, onboard charger, DC-DC converter, and powertrain controller. Tesla would produce the powertrain components in California then ship them up to Ontario, Canada where the RAV4 is assembled and then it is shipped back to California to be sold.

Mariordo - Mario Roberto Durán Ortiz, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

This sounds like the best of both worlds when it comes to reliability. An overbuilt Toyota paired with the simple Tesla drive unit. One would think that with only four moving components it should be easy for the drive unit to last hundreds of thousands of kilometers. However, when the RAV4 EV was in development Tesla had only been a company for just over 5 years. This means that any issues Tesla had with the early Model S drive units would also be an issue with the RAV4 EV drive units. There were many issues…

First there was the motor bearings that failed creating excess side to side play in the motor rotor. This play caused the motor to emit a “milling” noise when moving. Another likely result of the play is the motor rotor coolant seal failing allowing coolant into the motor and inverter case. This coolant would not only damage the bearings further but also destroy the inverter if enough leaked into the case. Another problem is due to the use of an induction motor. With a permanent magnet motor the rotor is a permanent magnet and is spun by the magnetic field generated by the current running through the stator windings, this does not produce any excess current in the rotor(This style is used by other Tesla drive units and most other EV manufactures). However, with an induction motor the rotor is not a permanent magnet. The rotors magnetic field is generated by the current flowing thorough the stator inducing a magnetic field in the rotor. This generates excess current in the motor rotor. To prevent this current from damaging the motor bearings a silicon nitride bearing is used. This means that the next path to ground is the drive unit input shaft bearings. Tesla knew this when they were designing the motor and put some brushes on the motor shaft to ground out any current before it can get to the input shaft. This was not enough to fully remove all the current and the input shaft bearings are damaged as it makes its way to ground.

These issues affected a large majority of Model S and RAV4 EV drive units. Tesla revised the drive unit many times to fix the problem however when the drive units are replaced by Toyota under warranty they do not get the latest revision. This becomes a problem when the drive units fail in places that do not have a RAV4 EV certified Toyota dealership or the car is no longer covered under warranty.

This brings us to the reason I was working on a Rav4 EV.

A customer had his Rav4 EV towed in from an island off the coast of Vancouver to have the motor bearings and seal replaced. To confirm that the coolant seal is leaking you can take the motor rotor speed sensor out and inspect for moisture. The easiest way to get to the sensor is to go through the passenger side wheel well. As you can see this motor has coolant on the sensor. So out the drive unit comes. This is surprisingly easy with only about two dozen bolts, three electrical connectors and two coolant lines. The drive unit does weight quite a bit so a lift table like in the picture makes this job significantly easier. Once I removed any miscellaneous brackets from the drive unit it was time to start disassembly.

This picture shows one of the benefits of electric vehicles. This unit contains the motor, inverter and gear reduction. When integrated together it can be a very compact package.

Behold… The Flux capacitor…. Ahem, I mean the inverter.

The disassembly.

The first thing to remove is the coolant manifold and line. The motor rotor has a toothed wheel for the speed sensor press fit onto the shaft. After that is removed we can carefully pry the cover off. All of these parts are made of aluminum and are not easy to find replacements for.

I could not get the motor rotor out of the drive unit with both sides of the case together. So if I couldn’t pull the rotor out I would have to push the rotor out. With a hammer. There are two temperature sensors located in the stator windings. The harness for these sensors passes though with the three HV connections for the motor. It must be unplugged from the inverter control board and pulled through the opening when the case is split.

To get to the motor shaft all of the gears will have to be removed from the case. First is the differential, then the output shaft and input shaft. Once the motor shaft is exposed it can be hit with a dead blow hammer to free it from the casing. The picture on the right shows the oil seal with the rotor removed.

Here it is. The rotor is finally out of the drive unit. Located on both ends of the rotor are the bearings. One end of the shaft has the spines that connect to the input shaft of the gear reduction. The other end of the shaft is hollow to allow for coolant to flow though.

Inspection and Repair.

I used a puller to remove the two bearings from the motor. A bearing installer tool was used to press the new bearings onto the motor shaft.

Something I noticed while the drive unit was being disassembled is that almost every single part is labeled with a part number. Some of them even have date codes on them. However just because they have part numbers does not mean that tesla will sell you the part. In fact the only parts that tesla will sell you on this drive unit are the external parts like the speed sensor, axle seals, coolant outlet and breather vent.

Bearing Info

These are the bearings that Tesla used inside the drive unit.

Almost all of the bearings are made by SKF. The one exception is the output shaft outer bearing, which is made by Schaeffler (FAG).

All of the bearings are C3 clearance.

Input Shaft Outer Bearing	SKF 6207/C3
Input Shaft Inner Bearing	SKF 6208/C3
Output Shaft Outer Bearing	FAG RNU2207E
Output Shaft Inner Bearing	SKF 6308/C3
Differential Outer Bearing	SKF 6310/C3
Differential Inner Bearing	SKF 6309/C3

Reassembly

Now that the bearings have been replaced it is time to start assembling the drive unit. After all the old silicone has been removed and all the parts have been cleaned it becomes time to put the input shaft, output shaft and differential all back in to the casing. When the new silicone is applied it is important to make sure the coolant passages are not blocked. With the 3 phase HV connections and temperature sensor hooked back up the inverter cover is reinstalled. Now the motor rotor is carefully slid back into the housing. The stator windings can be fragile. The motor end cover is reinstalled with more silicone and a new coolant seal is installed. Installing the coolant seal was probably the most difficult part of this whole job. The seal fits very tightly over the motor shaft and must be installed dry. Once the coolant manifold and seal are installed all that remains is the speed sensor, coolant line and motor mounts.

So what did I learn?

Simpler is not always better. There are just too many problems with these drive units. This is made extremely problematic when neither Tesla or Toyota want to service or sell parts to repair these vehicles.