Inside Toyota’s UA-UB80E/F torque converter - Transmission Digest

Inside Toyota’s UA-UB80E/F torque converter

The UB80E/F family of transmissions used in Toyota L4 applications, and the UA80E/F used in V6 engine applications, should not be confused with the AWF8G30 transmission. Although similar, they are significantly different. 

The converters used in these applications are like other known systems. Within this system, there are two very important sealing rings that need to seal properly for the converter to function correctly. The converter used in this article came out of a UB80E from a 2021 RAV4 2.5L (see Figure 1, above). 

From the case passage ID seen in Figure 2, this is a three-stage converter, with the stages being:

  1. Torque converter charge where fluid enters and fills the converter. 
  2. Torque converter return where the returning pressure going back into the transmission is then routed to a clutch exhaust valve located in the rear valve body. 
  3. A separate circuit to apply a multiple disc clutch assembly inside the torque converter. 
Figure 2.

The torque converter drives an off-axis pump. One of the important seals in the converter’s hydraulic system is in front of the drive gear support, as seen in Figure 3. This seals on the inside of the converter hub as seen in Figure 4. The other important seal sits on the tip of the turbine shaft (Figure 5). 

Figure 3.
Figure 4.
Figure 5.

Precision International tells us that the ring which seals inside the converter hub is a Japanese-based PEEK plastic compound, while the ring that is on the tip of the turbine shaft is a Polytetrafluoroethylene ring with a 15% graphite blend compound. These rings are designed to handle heat without shrinking. 

To begin seeing how critical these seals are, Figure 6 identifies these the circuits in the front of the transmission. Just a quick glance and you can see how important the ring is on the tip of the turbine shaft. It prevents TC charge pressure from intruding into the TCC apply pressure. 

Figure 6.

The TC return circuit is located below the stator shaft spline and the inner diameter of the pump drive sprocket support. The sealing ring that seals inside the converter hub sits right behind the converter hub seal. The front turbine shaft ring and the rear converter hub sealing ring maintain converter charge pressure. If the converter hub sealing ring is compromised, flow through the converter will change, dropping pressure and affecting torque transfer efficiency. 

With the converter cut open, each individual component can be inserted into place. Figure 7 shows the converter impeller (pump) and hub inserted first. This perspective shows the importance of the inside converter hub sealing ring: It forces the fluid to enter the return slots going back to and through the valve body. Without the seal, this return fluid will have an additional path to exhaust. 

Figure 7.

The return fluid is also part of the flow which is returned to the impeller through the stator, which is the next component seen in Figure 8. The turbine and damper assembly which includes a multi-disc clutch hub is the next component to be installed (see Figure 9). 

Figure 8.
Figure 9.

The multi-disc clutch assembly is built into the cover as seen in Figure 10. When this clutch assembly applies, it locks on to the turbine assembly driving the turbine shaft at engine speeds. The fluid pressure used to apply this clutch assembly comes out of the tip of the turbine shaft as seen in Figure 6. But there is one more aspect to the function of this converter that hasn’t yet been covered. 

Figure 10.

A closer look into the center of the multi-disc clutch assembly where the turbine shaft goes into two separate feed circuits can be seen in Figure 10. The deepest circuit closest to the cover is the clutch apply circuit. The next one up distributes converter charge pressure into this multi-disc clutch assembly. This pressure is constant and is used to push the apply piston into a released position. The TCC apply pressure works on enough surface area of the piston to overcome the charge pressure trying to release the clutch. With this further explanation of the function of the multi-disc clutch assembly, the importance of the sealing ring separating these two pressures becomes more evident. 

The TCC Apply pressure is controlled by the blue connector SLU solenoid on the valve body shown in Figure 11.

Figure 11.

As with all the shift solenoids and line pressure solenoids, this SLU solenoid provides hydraulic pressures that are proportional to the current that flows to the coil. The engagement of this multi-clutch assembly in this converter is controlled by this pressure regulation. 

In short, this is a busy torque converter, much of which relies on two sealing rings for it to function correctly.

You May Also Like

How to fix GM 6T70/Ford 6F50 rattling noise with transmission in gear

A rattling noise is coming from the transmission whenever the engine is running and the transmission is in gear.


The complaint

A rattling noise is coming from the transmission whenever the engine is running and the transmission is in gear.

The cause

Too much clearance develops between the pinion bearing and the park gear—refer to figure 1, above—which causes the park gear to rattle against the differential pinion gear.

The importance of the follow-up road test after transmission replacement

A 2002 Lexus RX300 equipped with a 3.0-liter V6 engine and U140F transmission was brought into our facility with a few concerns. The customer said that “it has a leak, a grinding noise when taking off from a stop, and it just doesn’t seem to shift right.” Related Articles – Sonnax introduces Sure Cure Kit

RR Tech Feature Oct
Tips and tricks for Chrysler switch valve plug testing

As technicians, we are often faced with build issues that can sometimes be frustrating at first. But with a little ingenuity, these frustrations can be turned around and made simple. Related Articles – ETE Reman: Ever expanding – Shift Pointers: Nissan’s no throttle response – Jatco/Nissan JF011E critical wear areas and vacuum test locations In

GM 8L90 #7 Check-ball: The overheat that saved the day

Beginning in October of 2015, GM removed the #7 Check-ball from the solenoid valve control body in the 8L90 transmission (see Figure 1). This was done in conjunction with the elimination of the Lube Override Enable Valve from the upper valve body as shown in Figure 2. Related Articles – ZF 6HP26: A torque calculation

Shift Pointers: Nissan’s no throttle response

Nissan vehicles using continuously variable transmissions (CVTs) are notorious for defaulting to a no throttle response when the vehicle is engaged into gear. There are several malfunctions that can cause this protective failsafe feature to be initiated. A brake switch (stop lamp switch) stuck on, a double-footed driver, blown or incorrect brake bulbs, and wheel

Other Posts

Raybestos offers high carbon torque converter wafer for Ford 10R80

Raybestos has begun offering a high carbon torque converter wafer for Ford 10R80 transmissions. Related Articles – Raybestos introduces 10R80 conical torque converter wafers – 13 BorgWarner OEM/S solenoids move to Rostra – Gray Tools releases insulated socket sets According to the company, it is a bond-in solution that flexes and conforms to fit to

Podcast: Talking CVTs with Transtar, part 1

CVTs, or continuously variable transmissions, have long been a hot topic in the transmission repair industry, but we can safely say they’re here to stay. So what do you do when one shows up at your shop? In this podcast, with Dave Hritsko of Transtar as featured guest, we dive in to the ins and

Back to square one: When a transmission replacement doesn’t fix the problem

The subject of this article is a 2002 Ford Ranger with a 3.0L V6 engine and 5R44E transmission. There were 191,622 miles on the vehicle when it arrived at our shop. The owner said that the transmission was not shifting correctly and the OD lamp was flashing. Related Articles – Watch: Replacing a transmission and

Tips for success with the GM transmission fast learn process

This article is about failure, something we all experience from time to time. If you are attempting to perform a fast learn process on a GM eight-, nine-, or 10-speed transmission, you may have that temporary feeling of failure, as this process can bring on frustration quickly. Let’s talk about what the fast learn process