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The World’s First 8 Speed Automatic Transmission

Monday, December 1, 2014 - 08:00
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The Aisin AW Co., LTD has consistently been the first to market with several different types of automatic transmissions. The longitudinally mounted 8 speed automatic transmission called the TL-80SN (figure 1) is one of these transmissions. It is being used in a variety of Lexus vehicles as far back as 2007 and is now in the 2014 Cadillac CTS. Lexus refers to this transmission as the AA80E transmission.

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A year later ZF released their 8 speed transmission (figure 2) in BMW’s 760Li vehicle and is making quite a splash these days. It is almost easier to list the vehicles not using this transmission as opposed to those that do.

But the TL-80SN is a sleeper in that you do not hear much about the transmission but then you suddenly have one come into your shop and you do not know much about it. This article is designed to get you familiar with this unit so this doesn’t happen to you.

Unlike the ZF8HP transmission, this unit has a pressure tap for each of the clutch and brake assemblies as well as for lube pressure and main line pressure (figures 3 and 4). From a diagnostic stand point to have all these taps available is terrific. Line Pressure is checked between 10°C-80°C (122°-176°F). Drive and Reverse @ Idle: 52-64psi. Drive @ stall: 213-241psi and Reverse @ stall: 226-254psi. Clutch pressure should be close to line at full apply

Another plus is the computer is mounted externally so the external wires going to the transmission (figure 5) allows for checking speed sensor signals and solenoid commands. A chart in figure 6 can be used for bench testing the internal electrical components. Solenoid resistance values are checked at 20°C (68°F).

There are 3 speed sensors in this transmission (figure 7). All 3 are Hall Affect Speed Sensors. The NT is the Turbine or Input shaft speed sensor which is excited by teeth on the input shaft. The NC3 is an Intermediate Shaft Speed Sensor and is excited by the C3 Clutch Drum. The SP2 sensor is the Output Shaft Speed Sensor excited by the rear planetary ring gear integral to the output shaft. These Hall sensors are supplied with battery voltage. When checking these sensors with an O-scope, set tool to 5 Volt divisions at 2 milliseconds. A clean .5 to 12.5 volt pulse should be seen.

Gnd. in the chart indicates placing your negative meter lead to a good known body ground.

The Transmission Pressure Switch (TPS1- figure 8) is a normally open pressure switch. It monitors SL1 pressure. If checking this switch while in operation (connector plugged in and you are back probing wire 17), there will be less than 1 volt on this wire in 1st through 5th gears and will read near 12 volts in 6th, 7th and 8th.

In figures 3 and 4, there are two possible fluid fill locations. A fluid level check plug is located in the bottom pan as seen in figure 9.

The fluid fill procedure needs to be performed within a specific temperature range and is accomplished in the following manner.

Procedure for an entire transmission fill:

1.   Lift the vehicle up while keeping a level state.

2.   Remove the refill plug and overflow plug.

3.   Fill the transmission through the refill hole until fluid begins to trickle out from the

      overflow tube.

4.   Reinstall the overflow plug.

5.   Adjust level by using SST 09843-18040 to connect terminals 4 and 13 for non-

      air-suspension vehicles and 4, 11and 13 for vehicles with air-suspension in the DLC3

      connector shown in figure 10.

6.   Start the engine

7.   AC Must be turned off

8.   Slowly move the shift lever from P to S, then move the shift lever from the 1 to 8.

      Then return the shift lever to P.

9.   Move the shift lever to the D position, and quickly move back and forth between N

       and D (once per less than 1.5 seconds) for at least 6 seconds.

10. This will activate the fluid temperature detection mode.

11. Indicator light (D) remains illuminated for 2 seconds and then goes off.

12. Return the shift lever to the P position and disconnect terminals 13 (TC) and 4 (CG) –

      non-air susp. application

13. Return the shift lever to the P position and disconnect terminal 13 (TC) with air susp,

      applications

14. Idle the engine to raise the temperature of the ATF.

15. When the indicator light (D) turns on, lift the vehicle up immediately (off = temp too

       low, blinking temp too high).

16. Perform fluid level inspection while the D indicator light is on.

17. Remove the overflow plug at the proper fluid inspection temperature, check the fluid

      amount.

Fluid capacities are as follows:

Transmission pan and drain plug removal............. 3.2 liters (3.38 US qts. 2.82 Imp. qts.)

Transmission valve body removal......................... 4.2 liters (4.44 US qts. 3.70 Imp. qts.)

Torque Converter removal..................................... 6.7 liters (7.08 US qts. 5.90 Imp. qts.)

Entire Transmission assembly................................ 9.9 liters (10.46 US qts. 8.71 Imp. qts.)

This transmission requires Toyota Genuine ATF WS transmission fluid.

There is an interesting tag on the transmission as shown in figure 11. This is called the QR label and it contains encoded automatic transmission property information such as fluid pressure characteristics compensation values. This 60 digit compensation code is used to improve the initial quality of the shift after the computer or transmission has been replaced. In short, you need to have Toyota’s Intelligent Tester to input this data to.

The procedure is located in the “A/T Code Registration” utility. It then simply walks you through several steps like making sure you are in Park, vehicle is not moving, the engine is off and the ignition is on. It will then ask if you would like to set the compensation code or read the compensation code. Once all 3 columns and 4 rows of digits are in place (whether you manually inputted the data or scanned it in) you instruct the tool to save the information. You then navigate your way to a Sub System Utility where the function is located to reset the compensation code and initialize the TCM ECU.

Shift timing control, Clutch to Clutch Pressure Control, and Line Pressure Optimal Control are all associated with this compensation code. And as with many of Toyota/Lexus computer controlled transmissions, the TCM ECU also contains a program called AI (Artificial Intelligence) which is used to adapt to the operators driving habits and road conditions. Lock-up Timing Control and Flex Lock-up control in previous transmission are features also used in this 8 speed transmission. Other programs that are available are Neutral Stop control, Coast Downshift Control, Manual Shift Control called the Multi-Mode Automatic Transmission Control and Power Train Cooperative Control.

An extra note on the Neutral Control, most other manufacturers partially disengage 1 clutch for a neutral control operation. ZF for example performs a 20% decoupling of the A clutch with their 6 speed transmission and the B clutch with their 8 speed transmission. The A6MF1 in Hyundai vehicles reduces UD Brake pressure. This TL-80SN operates the SL1 and the SL5 solenoid to half engage two clutch assemblies for a Neutral Control; the C1 and B2 clutch. Direct inputs to the ECT ECU needed to control this operation are all 3 speed sensors, transmission fluid temperature and the Park/Neutral Position Switch. Network inputs would be the A/C Switch, Crank signal, Accelerator Pedal Position, Engine Coolant Temperature, Stop Light Switch, Yaw-rate Sensor, Deceleration sensor and Master Cylinder Pressure Sensor. What this means to you and I is, if any of the items are skewed or malfunctioning, it may have an affect with the proper operation of the Neutral Control strategy.

Figure 12 identifies the location and identification of the solenoids on the valve body. The SLT is a line pressure control solenoid. The SLU controls both TCC and B2 Brake apply. The SL1 controls C1 Clutch apply, SL2 the C2, SL3 the C3, the SL4, the C4 and the SL5 the B1 Brake. From this review of the solenoids and the clutch they operate you can see they are using three driving clutch assemblies and two brake clutch assemblies to achieve reverse and 8 speeds forward.

The placement of the clutch assemblies begins with the B1 brake located right behind the pump (figure 13). Next to come out are three driving clutch assemblies. From left to right; the C1, C3 and C4 (figure 14). Then next two components is a one-way-clutch (F1) and the B2 brake clutch assembly (figure 15). The last clutch assembly all the way in the rear of the transmission is the C2 driving clutch (figure 16).

Having now provided both solenoid and clutch identification and location, the application chart in figure 17 becomes helpful in knowing what is on and off and when.

When you compare solenoid activity with clutch apply, you’ll see how each of the solenoids have control over their respective clutch assembly. If you read a previous article in Powertrain Pro about GM’s 6T40 series transmissions, I made a comment about gear ratio codes being replaced with solenoid performance codes. This transmission utilizes the same strategy. You will not see P0731, 732 etc. for gear ratio errors. You will pull solenoid performance codes in their place.

One helpful last point related to solenoid codes is the way these solenoids may be identified. The SL solenoid will be referred to as the TCC Solenoid while the SLU will be referred to as the TCC Pressure Control Solenoid. SL1 may be called Solenoid A, SL2 as B, SL3 as C, SL4 as G, SL5 as H, SLT as D and the SR as E.

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