Over the past few years, owners of Toyota Highlander and Sienna minivans with the direct shift 8AT transmissions have experienced many problems. This involves the eight-speed transmission known as UA80, UA80E, and US80F. As a result, a class-action lawsuit has been filed in California. It covers over 1 million Toyota 8-speed transmissions.

Chevrolet Performance has adapted the production-based 8L90-E eight-speed automatic transmission for use with our LT1, LT4, and LT5 crate engines. 19419039 8-SPEED AUTOMATIC. It’s no secret that the GM 8-speed transmission is not great. Also known as the 8L90 and 8L45, the 8-speed pairs to rear-wheel-drive architectures in GM’s bread-and-butter products, including. The Hydra-Matic 6L90 (production code MYD) is a six-speed automatic transmission produced by General Motors for use in rear- and rear-biased all-wheel-drive vehicles with a longitudinal powertrain. 8-speed automatic transmission (AT) for high torque capacity SUV Achieves 8-speed with equivalent installation to the 6-speed AT, based on the conventional high torque capacity 6-speed AT Improved fuel efficiency and vehicle performance by weight saving and efficiency improvement in addition to the optimal gear ratios.

The issue has been owners of either 2017 and up Highlanders and 2017 and up Sienna minivans experience harsh or delayed shifting, delayed acceleration, hesitation, jerking, unintended acceleration, lurching, and excessive RPMs before upshift occurs. The plaintiffs claim Toyota actively concealed 8AT automatic transmission defects according to CarComplaints.

The dealership said the Toyota Highlander was performing normally

RELATED: 2020 Toyota Highlander: Consumer Reports Biggest Knocks Aren’t Dealbreakers

Florida plaintiffs purchased a new 2018 Highlander XL. Within the first few hundred miles, they experienced “hesitation and surging while driving at low speeds, in stop-and-go traffic, and as they accelerated to join the traffic flow.” When they took the Highlander into the dealership they were told the vehicle was performing normally.

At 2,000 miles, 8,730 miles, and another time the Highlander was returned to the dealership. Each time the owners were told the car was performing normally. After the last return to the dealership, a senior technical service advisor allegedly said the eight-speed transmission problems “were common to Highlanders and other Toyota models and were well known to Toyota and its dealers.”

A Toyota technician “found it to perform like a known good vehicle”

At 11,930 miles it was returned yet again. The dealer didn’t inspect the Highlander but informed the owner that a “Toyota District 2 Fixed Operations Manager” did. He reported that he “found it to perform like a known good vehicle” and did “not exhibit any warrantable concern.”

He continued, “Today’s vehicles . . . are driven by wire which means they do not have a throttle cable so they may exhibit very slight lag due to the ECM processing. The current eight speeds transmissions are geared to keep the engine in an optimum operating condition which may not meet the customer’s desired performance but in every case, a little extra pressure on the gas pedal improves responsiveness, and customer satisfaction can usually be obtained.”

In October 2019 the owners took the Highlander to a different dealership. The technician there said the transmission problems were caused by an internal failure on the transaxle assembly. They “replaced the transaxle assembly and associated parts per bulletin T-SB-0160-18.”

Since that transaxle replacement, the owners say the Highlander performs worse

Since that transaxle replacement, the owners say the Highlander performs worse than before. In another bulletin, Toyota said some 2017 Sienna minivans can experience a lack of power. Additionally, high RPM at shift points 2-3 shift, hesitation in lower gears, and stays in gear too long before shifting.

Two more bulletins were issued before Toyota technicians were advised to replace the transmissions with remanufactured transmissions. The lawsuit alleges that the 8AT transmission makes driving vehicles it is installed into dangerous and hazardous to passengers. It also says surrounding property is in danger from the transmission hesitation, jerking, lurching, and acceleration issues.

General Motors has been a leader in pushing for additionalgears in automatic transmissions and there has been both success andfailure. How did we go from 3 and4-speed transmissions from the 1960s through 2000s to 11+ speeds in unitstoday? The increase in gears withintransmissions is tied to key objectives including (1) lowering vehicle emissionstandards and (2) maximizing driver comfort. Some of the transmissions with 8-speeds were only integrated within themanufacturer’s lineup for a handful of years but it’s worth discussing giventhe millions of these units on the road.

The 8-Speed GM Transmission

The GM 8L90 and 8L45 transmissions were developed to replaceearlier 6-speed automatic transmissions in General Motors rear wheel drivevehicles.

• The 8L90 was introduced in 2014 in vehicles likethe Chevrolet Silverado / GMC Sierra pickups, the GMC Denali, the Corvette andCamaro, and several Cadillac applications.
• The 8L45 is a lighter transmission introduced in2016 for vehicles equipped with a V6 engine such as the Chevy Camaro, CadillacCT6 and the Chevy Colorado pickups.

Having eight speeds allows the transmission to stay in the“sweet spot” of the RPM power band and also gives 5% better gas mileage thanthe earlier 6-speed transmissions. There’s probably a 15-20% improvement between the 8-speed transmissionsand their 4-speed ancestors.

GM 8-Speed: Success or Failure?

Since introduction, there have been a number of complaintsabout the 8L90 and 8L45 units. Thesecomplaints have to do with the tendency to “shudder” during light throttleacceleration between 20 and 80 miles an hour. Although a wide range, the intermittent and unpredictable transmissionissue was a cause for concern for many buyers of these vehicles. In some cases, this shudder is severe enoughto cause hard shifting and violent jerking between shifts. In most cases the shudder is less abrupt andleads to a sound similar to driving over a “rumble strip” even though thevehicle is on smooth pavement. In allcases, the transmission is having problems properly shifting between gears andtherefore gives a very erratic ride. Youcan be sure the transmission’s failure to realize a smooth shift is not justuncomfortable for you, but also causing damage within a transmission. Premature wear of the unit due to addedfriction and added heat is a likely outcome. These long term results have not been realized given most of thevehicles have yet to realize 100,000 miles in their lifetime.

Can a fluid exchange or redesign avoid a major liability for GM?

We are not lawyers, so it is unknown whether General Motors has a valid legal liability on its hands. Several class actions suits have been filed against GM in regard to the 8L90 and 8L45 transmissions. In the meantime, General Motors has issued service bulletins to address the problem. General Motors believes that the answer is to do a transmission fluid service to replace the original Dexron VI transmission fluid with a newer low viscosity fluid. In recent years, fluid complexity has increasingly become an area of attention to support the redesign of transmissions traditionally driven from hydraulic stimuli to electronic control. The first attempt at fixing the unit issues with fluid chemistry involved replacing with a Mobil 1 “Black Label” synthetic fluid (GM part number 19355656), and later a “Blue Label” Mobil 1 LV ATF HP fluid (GM part number 19417577). This involves using a machine to flush the old transmission fluid out of the vehicle and then pumping in the newer fluid.

The older Dexron VI fluid has issues being hygroscopic,allowing moisture to build up inside the transmission. Since the service bulletins have come out,many owners have found that the new fluid does indeed fix the shudderissue. After driving for a week or so,the new fluid cleans up many of the internal issues as the adaptive shiftalgorithms go through their “relearning” process. However, this process has not fixed the issuein all vehicles that have had the fluid replacement completed. In these cases, the next step is likely toreplace the torque converter which has become glazed by the excessive temperaturesgenerated by the shudder.

8 Speed Automatic Transmission Problems

Note: a copy of the GM service bulletin 18-NA-355 can be found online.

Local Transmission Shop to the Rescue!

The problem with the 8L90 and 8L45 transmissions iscertainly not unique, and really points out the importance of using the righttransmission fluid! If you are takingyour vehicle in for a transmission service, make sure your localtransmission shop understands the proper transmission fluid that isspecified for your vehicle and is not using a cheaper generic fluid. At Advanced Transmission Center, we work witha number of fluid manufacturers in order to ensure that we are using the properfluid for your vehicle. Don’t settle fora cheaper alternative, as it can cause significant internal damage to yourtransmission and cost you a lot more in the long run! The adage, “you get what you pay for” is verytrue in transmission repair. There’salways the “cheap” or “budget” transmission repair solution, but is it reallyworth it if the problem isn’t’ actually resolved? The 8-speed transmissions are going intorecent vintage vehicles that have high value and extremely high repaircosts. It’s tempting to opt for aneconomic solution. In the case oftransmission repair, it is important to trust whoever is most competent and trustworthy.

GM/Chevy Transmission Experts

8 Speed Automatic Transmission Fluid

The Advanced Transmission Center team consist of technicianswho are specialists in GM vehicles. Wecomplete more repairs on GM vehicles than any other manufacturer. Our Chevrolet/Chevytransmission repair expertise is the best in Denver. We serve over 300 customers with Chevrolet/Chevy,GM and Cadillac transmission rebuild needs each year between our multiplelocations.

If you own a vehicle equipped with an 8L90 or 8L45 transmission and the vehicle is still under warranty, contact your dealer to have repair service performed. If not, contact Advanced Transmission Center at either of our locations and we’d be happy to help! Unlike dealerships or many independent repair shops, we are transmission specialists trained to fix issues related to a vehicle drive-train. You can reach out to either location that is most convenient for you.

8 Speed Automatic Transmissions Rav4

Advanced Transmission Center – Lakewood 1194 S Pierce St Lakewood, CO 80232 PHONE: 303-816-3856 Manager: Keith

Advanced Transmission Center – Westminster 3686 W. 72nd Ave Westminster, CO 80030 PHONE: 303-647-5257 Manager: Anthony

Pleasegive us a call or send us a message ASAP. We look forward to serving your vehicle drivetrain and transmissionneeds. Over 35 years, our goal remainsto be “Geared for Customer Satisfaction!