Making a plug-in hybrid vehicle is quite complicated. There’s a combustion engine and an electric motor that need to be meshed together. Different automakers employ disparate strategies for how to handle the process, with varying levels of success.
Volvo, being Swedish, did things differently. The approach was not necessarily bad, but different. While companies like Volkswagen and BMW sandwich an electric motor somewhere between the gas engine and transmission, Volvo basically splits its all-wheel drive PHEVs in two: the front half is powered by a 2.0-liter gas engine, while the back half is exclusively powered by an electric motor.
That electric motor is integrated into something that the company calls an Electric Rear Axle Drive (ERAD). The component has proved to be problematic ever since its introduction in 2015, with many owners experiencing catastrophic failures and facing huge repair bills, according to forums, social media posts, mechanics and technical journals published by Volvo.
Volvo Drive-E Electric Rear Axle Drive (ERAD), 2016
Photo by: Volvo
The ERAD drives the rear wheels independently of the front one, providing all-electric driving and enabling all-wheel drive when the gas engine is running. It’s a very clever system that eliminates driveline losses associated with systems that integrate the e-motor into an automatic transmission.
It’s also complicated, which can scare off traditional mechanics when it does go wrong, according to some Volvo technicians I spoke to for this story. This, coupled with repair bills that can easily go over $10,000 if done at a Volvo dealer, could scare potential customers away from the automaker’s plug-in hybrid offerings.
I don’t blame them. Some owners have had their ERADs replaced multiple times in the span of less than 100,000 miles, while others have driven well over 200,000 miles without a hiccup. That said, it’s hard to pinpoint exactly how common this issue is. If you only read what affected owners have to say, it’s very bad. However, after speaking with some mechanics and technicians who repair Volvos for a living, things get a lot more nuanced.
One shop in Bucharest, Romania, said it has had to replace roughly eight ERADs in a month, while another Volvo specialist in Canada said it hasn’t seen a failed ERAD in over a month. I also contacted Volvo directly to get an official word on how many warranty repairs it has had to do since 2015 and what improvements have been made to lower the failure rate. I have not heard back from the company until publishing time.
All of this hasn’t stopped me from buying a plug-in hybrid Volvo V90 with my own money. Despite the potential issues, I think it’s a fantastic family hauler with excellent fuel efficiency and enough electric range for the daily commute.
After talking to several Volvo technicians and doing a lot of research on the Volvo ERAD failures, my conclusion is that there’s light at the end of the tunnel, and it could be much simpler than one would expect. So let’s dive deep into what causes a Volvo ERAD to fail and what owners can do to mitigate the issues.
What is an ERAD?
The electric rear axle drive is a single unit that integrates an electric motor and a single-gear transmission that drives the rear wheels. It gets power from a lithium-ion battery pack located inside the transmission tunnel.
All SPA-based plug–in hybrid Volvos from 2015 onward have an ERAD at the rear. This includes the XC90, XC60, S60, V60, S90 and V90, the plug-in versions of which have had different names over the years. Depending on the market and year, the models were called Twin-Engine, T6 Recharge, T8 Recharge, Extended Range or simply T8 AWD.
2016 Volvo XC90 T8 Twin Engine. The blue parts are powered by electricity, while the green parts are combustion-powered.
Photo by: Volvo
The ERAD is not physically connected to the front wheels. This means that an SPA-based Volvo PHEV can be rear-wheel drive when there’s enough juice in the battery, front-wheel drive when the battery is depleted and all-wheel drive when the gas engine and electric motor are working together.
What are the symptoms of a failed ERAD?
Common symptoms of a failing ERAD include unusual noises like grinding, clicking or knocking. Hesitation or jerkiness under acceleration can also occur, with the final blow being a loss of rear-wheel propulsion. Usually, if the rear electric motor fails, the car can still drive using the gas engine and automatic transmission that drives the front wheels.
That being said, it’s worth noting that most issues start in the transmission part of the ERAD, and if they’re caught and repaired in time, they can be repaired for far less.
What model years are affected by failing ERADs?
Since its introduction in 2015, there have been three versions of the ERAD. The first two are more or less the same, while the third is completely different. All three have had their own issues, but generally, the later versions are more reliable than the first-generation models.
First introduced on the second-generation XC90 SUV in 2015, the initial version of the ERAD had 82 horsepower (60 kilowatts) and 177 pound-feet (240 Newton-meters) of torque. Just a year later, when the car made it to the United States for the 2016 model year, power was raised to 87 hp (65 kW). On the transmission side, there’s a built-in clutch mechanism that engages and disengages the electric motor depending on the driving scenario.
XC90 T8 Twin Engine – A Siemens-made integrated electric drive unit (2015)
Photo by: Volvo
All of the mechanics and service technicians I spoke with for this article said that this initial version of the ERAD is the most problematic. The most common issues are related to the clutch mechanism and thermal sensor. Anecdotal evidence points to the XC90 model being the most affected, and that may have something to do with the fact that it’s the heaviest of all the SPA-based Volvos. Furthermore, the XC90 was the only ERAD-equipped Volvo for the 2016 model year, before the 2017 S90 and V90 joined the list.
Getting back to the issues, the clutch inside the transmission can degrade over time, sending metal flakes into the differential fluid. This makes the fluid more abrasive. The degraded fluid then rubs on the splines of the shafts, leading to even more flaking. This slowly damages the bearings, which results in more heat and ultimately leads to the weakening of the C-clip that holds the main differential shaft in place. When this happens, the differential shaft no longer aligns with the output shaft of the electric motor, which can damage the splines on the e-motor shaft, rendering the whole ERAD useless.
The electric motor in the ERAD is not repairable, but the transmission part is, as attested by several Technical Journals issued by Volvo to address various issues. The clutch pack, differential and some bearings can be replaced.
That said, there is another issue with these first models, and that’s the temperature sensor, which is embedded in the electric motor winding. This sensor has a habit of failing, and when it does, the whole ERAD needs to be replaced, even if there’s nothing wrong mechanically. One of the Volvo technicians I spoke to said that all of these might fail eventually, and almost all of them will be XC90s.
This second iteration is almost identical to the first and retains the clutch mechanism. However, the internal components are more resilient, according to the technicians I spoke to, leading to lower failure rates.
Volvo ERAD2, made by GKN Automotive (2016)
Photo by: GKN Automotive
Some first- and second-gen ERADs were fitted with a failing C-clip, and they can be fixed by changing the affected part, but only if it’s caught in time. Furthermore, there’s a technical journal that addresses a whirring noise caused by a sensor disk.
This is a completely redesigned unit, with more power, more torque, and a different mode of operation. With 143 hp (107 kW) and 228 lb-ft (309 Nm) of torque, the latest ERAD ditches the clutch pack in favor of a permanently engaged planetary gearbox.
The rear drive unit on my 2023 V90 T8 Recharge was made by Schaeffler in China.
Photo by: Iulian Dnistran / InsideEVs
When coasting, the ERAD simply matches the speed of the vehicle without producing any drive force. In similar scenarios, the clutch in the previous versions disengaged the transmission for true coasting.
The latest ERAD is by far the most reliable, and if you’re looking for a plug-in hybrid Volvo, this is the one you should be looking for, mechanics say. Besides the higher output of the electric motor, this version can be identified by the larger battery capacity (18.8 kilowatt-hours versus 11.6) and the Google-based infotainment system instead of the Sensus version.
That said, it’s not perfect. Some early units were shipped with insufficiently tightened bolts, which allowed the differential fluid to leak, damaging the gears inside. There’s also a technical journal regarding knocking. According to Volvo’s instructions, this can be fixed by adding a wave spring inside the differential housing instead of replacing the entire ERAD. However, this means the drive unit has to come out of the car, but Volvo will cover the repair bill if it’s under warranty.
Change your differential oil. That’s what all the mechanics I spoke with told me about prolonging the life of Volvo’s ERAD, no matter what car or model year involved. Specialists recommend changing the fluid once every 30,000 to 60,000 miles to reduce wear and tear, and that’s exactly what I did recently on my 2023 V90 PHEV, which has the latest ERAD version.
The car has roughly 38,000 miles on the clock, and what came out of the rear differential was a bit of a surprise. The fluid was black instead of honey gold, and there were far more metal flakes on the magnetic sump plug than I expected. I like to think that by doing this first fluid change, I avoided catastrophe and a huge bill. But to be sure, I’ll change the fluid again in the next 7,000 miles or so.
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Source: Iulian Dnistran / InsideEVs
I would imagine a previous-generation ERAD with over 50,000 miles on the clock looks considerably worse. But because Volvo doesn’t include a diff fluid change–or an automatic transmission fluid change, for that matter–in the official servicing schedule, customers go on their merry way thinking the maintenance is easy and cheap. This follows a worrying trend in the industry, where automakers have stopped recommending differential and transmission fluid changes even when the evidence overwhelmingly suggests that “lifetime” fluids are a marketing myth.
If you’re like me and want to do a fluid change on your driveway, keep in mind that the first and second versions of the ERAD need one type of fluid, while the fluid for the third version has a different part number.
Also, it’s important to reiterate that this is not a catch-all solution. The failing temperature sensor can bring a hefty repair bill, no matter how often you change the diff fluid.
How many cars are affected by failing ERADs?
Nobody knows for sure. If you read forums and owners’ groups, the issue tends to be exaggerated because people who have had problems tend to be more vocal about their issues. That’s not to say the problems aren’t real. The repair shops I spoke to acknowledged that there are issues with Volvo’s ERAD, particularly the first generation. As previously mentioned, some shops see a broken rear electric drive unit once every few months, while others have at least one per month.
Officially, the rate and severity of failures have not prompted a recall, and Volvo has not answered my questions about the number of cases and potential causes until publishing time.
Conclusion
From my research, I found that many Volvo plug-in hybrid owners buy their cars new, and when the warranty runs out, the car is returned to the dealer. If something were to happen during this time, it’s the dealer’s problem, and issues will be fixed under warranty.
Not everybody can afford a new car, though, so some are going for a used PHEV, hoping they will lower their refueling costs. I did that, so I can relate.
In this case, an extended warranty might be the best solution for those who don’t want the hassle of repairing the car when it goes wrong. However, with or without the extended warranty, it’s a good idea to have the rear differential fluid replaced immediately.
If you can afford it and you’re thinking about keeping the car for a long time, it’s not far-fetched to get the car to a competent workshop that can remove the ERAD from the car, inspect it, and fix any silent issues before they balloon into something bigger. This could cost a few thousand dollars, but it’s nowhere near as expensive as a full replacement.
Look, cars are complex machines, and things break. In the case of Volvo’s ERAD, it’s a game of chance, unfortunately. You might strike gold and drive a PHEV for hundreds of thousands of miles without a hiccup, or you can get very unlucky and change an ERAD every 20,000 miles.
Go for a pre-2022 model, and you might fall into the latter category. Get a 2022.5 and newer PHEV, and change its differential oil regularly, and you’ll have way better odds.
