Rear axle coupler assembly (part number 41303-28013) making very loud noise and vibration.

- Phoenix, AZ, USA

Vehicle began 'whirring' metal noise from underneath. Local mechanic said it was coming from rear differential. I took it to a Toyota dealer, they said rear differential coupler needs replacing ($2159) and drive shaft ($992). It seems the bearing ring inside this sealed unit has failed. Noise is continuous while driving, concern of part failure - we are taking vehicle on family vacation. Researching on - line it appears to be common problem with the Sienna's. Toyota had same issue with RAV 4's and issued recall but have not for the Sienna's. I called Toyota corporate in TX (got up 3 levels) to no avail, and it curt tone, they said they cannot help. Based on other similar stories on line from other Sienna owners, this seems to be a common very expensive design flaw problem with this vehicle.

- Kennebunk, ME, USA

My 2012 Toyota Sienna recently began making a loud whining noise from the rear axle area. Upon inspection, we were informed that the differential unit was failing and needed to be replaced. This would cost us between $2,500-$3,000. After some research, I discovered that this is a common problem with the Sienna, likely caused by a design flaw. The same unit was used on the rav-4, and after similar problems surfaced it was recalled and fixed by Toyota. Given the danger posed by failure of this part to a family vehicle, and the known existence of the problem by Toyota, it seems obvious that it should be immediately recalled and fixed by the manufacturer.

- Minnetonka, MN, USA

Service tech at the Toyota dealer said my electromagnetic coupler / viscous coupler and driveshaft ujoint seized. After further research online it seems its common. Wondering if Toyota would put out a recall?

- Brooklyn, NY, USA

Unit is producing a speed dependent whine from the rear differential consistent with a bearing failure in the viscous coupler. Issue first observed with approximately 98,000 miles on odometer. This appears to be a common component failure on many Toyota AWD vehicles manufactured in the last 15-20 years, and the component in question may be under-engineered to perform as expected in normal driving conditions. Replacement part costs $1300+ from Toyota, not including installation.

- Shoreview, MN, USA

Says my rear differential - viscous coupler- is bad and needs to be replaced at a cost oof at least $1,300 and that doesn't include installation. Happened just as car went over 100,000 miles and is covered in rav 4 bc had same problem but not 2012 Sienna nothing happened except it suddenly started not because of anything I did.

- Freeport, ME, USA

The rear viscous coupler on the AWD had gone bad and needs replacement. This part is the same defective part on the rav 4 that had an extended warranty coverage due to bad design but is not covered on the Sienna. This part needs a recall.

- Sauk City, WI, USA

The bearing for the viscous coupler has gone bad. It whines loudly when in motion, and the volume correlates with the speed. According to feedback from online this issue happens a lot. Toyota will not change the bearing ($50 plus labor). They will only change the whole coupler ($1800 plus labor) as they state the coupler is not serviceable. Multiple people have serviced the working coupler to change just the bearing. Toyota released a similar tsb for the rav 4 where the coupler failed.

- Orangeburg, NY, USA

My 2012 Sienna AWD xle has 103K miles and has a whirring noise coming from the rear differential area for a while now. The pitch and volume is proportional to speed and is louder as speed increases. My research tells me this is a common defect with the coupling bearings in front of the rear differential. It seems that rav4 owners got a recall for the same issue, but Sienna owners did not. Toyota has redesigned this part on later models to avoid the issue. Hope you can get this resolved. Thanks.

- Plano, TX, USA

Front axle leaking fluid

- Bridgewater, CT, USA

Rear differential has failed at only 60K miles. Well documented issue for AWD Sienna models yet no recall issued. Safety concern for this family of five.

- Wheaton, IL, USA

When coming to a stop going about 5 mph towards a stop sign, my van accelerated into traffic. Because the van jolted me into oncoming traffic, it almost caused an accident. It doesn't seem to matter whether I am braking or coasting, the van will accelerate uncontrollably.I have two children and not only am I putting their lives at risk, but mine also. I am not able to drive this vehicle due to how dangerous it is.

- Mountain Home, ID, USA

Rear differential coupler dysfunctional without no reason. All of the Sienna especially AWD are suffering from this issue.Toyota denies to cover it.

- Strongsville, OH, USA

While parked, driver began exiting vehicle and van began to roll and continued to roll when gear shift lever confirmed in park and brake continually pressed, eventually hitting a house.

- Greenville, SC, USA

All underwood components are not only vulnerable, but attractive to rodents. While parked overnight on 4 consecutive nights, rodents have chewed through wires despite attractive rodent poison in the engine bay, the poison is untouched and the wires are attacked every night. To date injector wires, sensor sires, fuel pump wires have been compromised, including sensors for the stability control system, which is disabled. I repaired damage by running new wires, clearing nests and set traps and poison, but now the the fuel system has been attacked and the fuel pump does not activate. 3 other cars parked in the same location for the past 5 months are untouched. Safety systems are likely to be compromised for any person who must park these outdoors.

- Edmond, OK, USA

Joining highway in a situation where vehicles giving way cause hesitation and then give way causing braking then acceleration repeatedly, transmission refused to downshift on kick down, vehicle would not accelerate, actually slowed significantly forcing following vehicles to brake.vehicle eventually began to pick up speed.generally poor response from transmission in all modes. Transmission drops out of drive at low speeds causing engine to race before taking up drive, very hard to operate vehicle smoothly.. excessive engine vibration and noise for this price point, known more refined diesels knocking from steering column on constant radius turns when making small steering corrections, detectable at low and moderate to high speed.

- Bayside, NY, USA