2018 Toyota Sienna transmission problems

POWER TRAIN

Vehicle: 2018 Toyota Sienna XLE AWD, VIN [XXX], approximately 112,000 miles. Component: Power Train / Automatic Transmission (UA80F 8-speed). The vehicle has developed a pronounced whining noise from the transmission that rises with road speed, accompanied by harsh/rough shifting. A Toyota dealer inspected the vehicle and diagnosed a failing transmission requiring replacement. The symptoms and diagnostic trouble codes match those described in Toyota TSB T-SB-0160-18 ("Transaxle Whine Noise, Harsh Shift, MIL ON, or Reduced Power") for the UA80 8-speed transmission. This is the same failure mode Toyota acknowledged in Customer Support Program ZJC, which attributes the defect to a washer/locking tab that was not sufficiently bent during assembly, allowing an internal nut to loosen and causing progressive internal damage. However, this vehicle's transaxle serial number falls outside the range covered by ZJC, so Toyota has not provided coverage despite the identical defect and symptoms. This represents a safety concern. Based on documented failures of this transmission across the UA80 platform, the condition can progress to loss of power, limp mode, or sudden loss of forward propulsion while driving — including at highway speed and without further warning — creating a risk of a crash or of being stranded in traffic. The vehicle has been maintained through authorized Toyota service. I am requesting that NHTSA investigate whether the UA80/UA80F transmission defect warrants a broader safety defect determination and recall, given the volume of similar complaints across affected model years INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA complaint #11750202 — an unverified report by a vehicle owner.

POWER TRAIN

Since owning my 2018 Toyota Sienna, I have experienced hesitation and erratic shifting with my transmission. I have the UA80E transmission which upon research others are experiencing issues with as well. It appears Toyota is not fully acknowledging the problem. The problem is a safety issue as sometimes when you go to quickly accelerate (merging, making a turn while starting from a stop, etc) the transmission hesitates and doesn't engage for a few seconds. This is an ongoing problem with the transmission. Toyota really needs to fix these transmissions!

NHTSA complaint #11745443 — an unverified report by a vehicle owner.

POWER TRAIN

My 2018 Sienna had developed a whining noise when accelerating. After taking it in to the mechanic, they advised the transmission was failing. Estimated price tag of $6500-7000 to repair. The vehicle has less than 140K miles. Looking at different issues with this make/model and year, it seems like its rather common. I bought a Toyota for its reputation of getting at least 200K if not more miles. I called both the dealer and Toyota themselves. Both said too bad, so sad - nothing they could do for me.

NHTSA complaint #11719964 — an unverified report by a vehicle owner.

POWER TRAIN

The contact owns a 2018 Toyota Sienna. The contact stated that while driving 30 MPH and ascending a hill, the vehicle started making an abnormal whining sound and hesitated while accelerating. The vehicle was driven to the dealer to be diagnosed. The vehicle was diagnosed with transmission failure. The manufacturer was notified of the failure. The failure mileage was approximately 126,000.

NHTSA complaint #11715126 — an unverified report by a vehicle owner.

POWER TRAIN

Transmission has been whining. A P27137F Code appeared and the vehicle is only in 2WD mode currently. Concerned to drive vehicle due to further damaging transmission or getting stuck while on the road.

NHTSA complaint #11711540 — an unverified report by a vehicle owner.

POWER TRAIN

My husband and I bought this van brand new 6 years ago. We have taken very good care of it and have had it serviced only at the dealership. We haven’t had any problem with the van outside of regular maintenance. On 10/29/25, I had a van full of children when I felt a slip in my acceleration and a warning light came on that read, “ A malfunction in the electronic control of the engine, throttle, or automatic transmission has been detected. Contact your dealer in order to have your vehicle inspected immediately.” Thankfully, I was able to get it to the parking lot. The van didn’t leave that parking lot until the next morning when we took it directly to the dealership. That is when we were told the solenoid and the transmission had gone out. We had to have the whole thing replaced. The van only had 89,388 miles on it.

NHTSA complaint #11708394 — an unverified report by a vehicle owner.

POWER TRAIN

Transmission Whine and Hesitation. Low gear it will hesitate from stop. Know issue with this transmission. There should be a recall on all ua80 transmissions.

NHTSA complaint #11678376 — an unverified report by a vehicle owner.

POWER TRAIN

Whining sound coming from vehicle while in drive and accelerator is depressed. Confirmed by dealership that the transmission is failing and needs replacement.

NHTSA complaint #11656942 — an unverified report by a vehicle owner.

POWER TRAIN

This is a reoccurring issue on numerous occasions but the transmission programming is a danger to drivers when it is in economy mode (the default setting when car starts up). The transmission constantly starts at a higher gear (3rd or 4th) and reduces throttle input from a stop. It makes for a slower takeoff when making a right turn on the stop sign because the engine would be lugging. Similarly when trying to overtake or merge lanes and you try to speed up the vehicle, the car does not want to downshift. The above mentioned problems are not there when eco-mode is disabled or the car is put into sport mode.

NHTSA complaint #11605484 — an unverified report by a vehicle owner.

POWER TRAIN

There has been a "whining" noise or "hum" upon acceleration noticed for several months to a year, could be longer, but getting worse over time. There is also a delay when pressing on gas for the vehicle to actually accelerate. I have had many instances where I am almost hit from behind because of this delay. Obviously the person's behind me have been following me entirely too closely, but nonetheless, scary. This is our primary vehicle for our family, which carries 4 precious boys. I am aware of the CSP already in place for this issue but have been told that my specific vehicle does not qualify for the customer protection program. That seems very odd given the amount of vehicle's listed as "affected"(83,700) sienna's and 66,500 highlanders. You cannot tell me that there are not more out there like mine that are having the SAME problems but being told "not covered". I do not think anyone should have to drive a vehicle with children in it that you are unsure when your transmission is just going to go out or fear getting hit from behind because of the delay in acceleration. Please please do something about this in order to hold toyota accountable!

NHTSA complaint #11581429 — an unverified report by a vehicle owner.

POWER TRAIN

The contact owns a 2018 Toyota Sienna. The contact stated while driving at an undisclosed speed, the vehicle hesitated while accelerating. Several unknown warning lights were illuminated. Additionally, the "Pull Over - Take to Dealer" message was displayed. The vehicle was taken to the dealer, where it was determined that the transmission needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure and confirmed that the VIN was not included in Customer Support Program: ZJC (Coverage for UA80 Transmission). The failure mileage was approximately 132,000.

NHTSA complaint #11513668 — an unverified report by a vehicle owner.

POWER TRAIN

The last week of September 2021 my husband notice a sound like water runing and a leak on the driver and passenger seats, we take the vehicle to the Dealer for an inspection on October 2nd. They said the AC hose was clogged for a spiderweb and the leak can create a mold. This mold can affect my family health. We informed to the insurance and we taked the vehicle to the Dealer for repair. They did an expensive special cleaning to Remove the mold, and disamble my entire vehicle, the worse is my vehicle still unassembled after 3 months at the dealership. All this happens with out any warning sign, symptoms or light. This vehicle is 3 years old and all services on time and by the same Dealership. My vehicle has a lot of technology but not warning about this AC clogged and damage my entire vehicle wich still on repair.

NHTSA complaint #11448917 — an unverified report by a vehicle owner.

POWER TRAIN

DELAY IN DOWNSHIFTING WHEN THROTTLE IS PRESSED. A DELAY OF 1 TO 2 SECONDS OCCURS THEN ABRUPTLY DOWNSHIFTS AND THE ENGINES REVS LOUDLY.

NHTSA complaint #11243088 — an unverified report by a vehicle owner.

POWER TRAIN

I WAS TURNING LEFT ON COUNTRY ROAD AT 25MPH THE CAR DECELERATE AND YELLOW WARNING CAME ON THE DEALER SAID THE CAR THOUGHT IT WAS GOING TO ROLL OVER THEY DID THE SOFT WARE UP DATE THE CAR STILL DECALRATE YELLOW LIGHT COME ON MOST OF TIME WHEN STARTING UP

NHTSA complaint #11210734 — an unverified report by a vehicle owner.

POWER TRAIN

TL* THE CONTACT OWNS A 2018 TOYOTA SIENNA. WHILE DRIVING APPROXIMATELY 45-50 MPH, THE ACCELERATOR PEDAL WAS DEPRESSED, BUT FAILED TO RESPOND. ADDITIONALLY, THE VEHICLE DECELERATED INDEPENDENTLY ON OCCASION. THE VEHICLE WAS NOT DIAGNOSED OR REPAIRED. LARRY H MILLER TOYOTA COLORADO SPRINGS (LOCATED AT 5115 NEW CAR DR, COLORADO SPRINGS, CO 80923, (719) 419-5832) WAS NOTIFIED OF THE FAILURE. THE CONTACT STATED THAT THE FAILURE RECURRED ON SEVERAL OCCASIONS. THE MANUFACTURER WAS NOT CONTACTED. THE APPROXIMATE FAILURE MILEAGE WAS 10,000. THE CONSUMER STATED THE WHILE BACKING OUT OF A PARKING SPACE, THE VEHICLE SUDDENLY STOPPED REVERSING AND THE ENGINE BEGAN TO REV UP AS IF THE GAS PEDAL WAS BEING DEPRESSED. THE VEHICLE WAS PUT INTO PARK AND BACK INTO REVERSE. THE ISSUE RESOLVED ITSELF. THE BRAKING SYSTEM WOULD SHUTTER WHEN IN SNOW OR ICE CAUSING THE VEHICLE TO VIBRATE VIOLENTLY AND LOSE TRACTION.

NHTSA complaint #11184028 — an unverified report by a vehicle owner.

POWER TRAIN

2018 TOYOTA SIENNA LE. CONSUMER WRITES IN REGARD TO DELAYED ACCELERATION WHICH IS CAUSING TRANSMISSION DAMAGE. *AS

NHTSA complaint #11175491 — an unverified report by a vehicle owner.

POWER TRAIN

THE VAN STRUGGLES TO ACCELERATE. THERE IS NO WAY TO TURN OFF ECO MODE. NO BUTTON IS AVAILABLE. VAN STRUGGLES TO GO UP HILLS , EXCELERATE THRU INTERSECTIONS AND ALWAYS HUNTING FOR GEARS OR STUCK IN A GEAR AND SOUNDS AND ACTS VERY HEAVY ON POWER TRAIN END. THERE IS AN OPTION TO TURN OFF ECO LIGHT.TURNING OFF ECO LIGHT DOES NOTHING BUT HIDE THE PROBLEM. WE NEED AN OPTION TO COMPLETE DISABLE ECO MODE WITH UPDATE OR WITH A BUTTON.

NHTSA complaint #11170282 — an unverified report by a vehicle owner.

POWER TRAIN

MY 2018 SIENNA LE IS EXPERIENCING ACCELERATION PROBLEMS. I HAD THE SOFTWARE UP DATED BUT AFTER APPROXIMATELY 1,000 MILES THE PROBLEM IS RETURNING. THIS PROBLEM IS ESPECIALLY UNSAFE WHEN MERGING ONTO THE HIGHWAY.

NHTSA complaint #11131655 — an unverified report by a vehicle owner.