Wednesday, April 26, 2017 Detailed Auto Topics
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Try to check the automatic transmission fluid on a later model Toyota and they may surprise you. Toyota, like several other manufacturers, has eliminated the transmission dipstick on many of their models. Servicing and checking automatic transmission fluid level now takes much more time and must be far more precise.

Transmissions without dipsticks

Proper fluid level indicated by fluid dripping from overflow tube

Toyota refers to these transmissions, without a dipstick, as overflow models. The term comes from the fluid-level checking method. We remove a check plug in the pan to see if fluid comes out. Unfortunately, we must consider several other factors to prevent a wrong reading.

With a level vehicle at the proper temperature, when we remove the plug, fluid slowly drips through the overflow tube. Too much fluid drains steadily when we remove the plug and no dripping means the transmission is low.

The fill plug may be on front or rear, left or right

Toyota also provides a drain-plug to empty the pan and we remove a separate fill-plug to add fluid to the transmission. The location of the drain and fill plugs vary, based on the vehicle model and the transmission used. To identify the transmission model, we read the option tag, normally on the door post of the vehicle.

Typical Toyota vehicle options tag, on left front door post

When do we check fluid level?

Transmissions require checking the fluid level, when we find a leak or when we service them. The lack of a dipstick makes these jobs more difficult but still within the realm of an accomplished home mechanic. They do not seal these transmissions, as some seem to report, and all transmissions benefit from a proper service. Both the fluid and filter are also replaceable on overflow transmissions. Some dealerships call the filter a screen, but this is a matter of semantics. When we service these transmissions or to check fluid level, we need some knowledge, a few special tools and a proper workplace.

Using the overflow method

To use the overflow method, several things are necessary. A vehicle has to be level when we remove the check plug. This is not optional and is very important. If the vehicle leans, we get a false reading. We also need a means to access the transmission temperature as outlined below.

Importance of vehicle level when checking fluid

Even when a transmission has a dipstick, a level vehicle and a known transmission temperature are important when we check transmission fluid. With the overflow transmissions, these factors become critical.

An unlevel vehicle gives the wrong reading

If the vehicle leans in the direction of the check plug, too much fluid will drain. This leaves the transmission dangerously under filled, even though it shows full. A vehicle leaning away from the plug, means we will overfill the transmission. Only a level vehicle will show the proper fluid level.

An elevated workplace allows easy access to the transmission but it must be level. Before lifting the vehicle, measure the distance from the rocker panels to the ground. If we use jack stands, measure the same spots and make sure the relationship of front to rear readings remain the same.

Measure height before and after lifting

For instance, before lifting, we measure six inches from the front rocker to the ground and seven inches in the rear. After lifting, if the measurement in the front is 20 inches, the rear should read 21 inches and equal side to side. We can allow for a difference of half an inch or less, from the driver to the passenger side. More than a half-inch normally shows a problem that should be corrected.

Fluid level is checked with the transmission at the proper temperature, idling and after shifting through all gears. We start the engine and with a foot on the brake, shift slowly through each gear. Next we must verify transmission temperature is correct, as outlined below.

The importance of fluid temperature

Without allowing for temperature, the level will not be correct)

An improper reading occurs when we do not consider transmission fluid temperature. Fluid expands as temperature increases and contracts when it cools. They design the overflow tube to read accurately at a narrow temperature range. A transmission warmer than specified allows excess fluid to drain. If not properly warmed, we will overfill the transmission, before fluid drips out. A transmission checked at the wrong temperature will not have the proper fluid level. This may cause shifting concerns and can damage the transmission.

The desired temperature range varies from model to model, even with the same transmission. Checking Toyota service data for the year and model we are working on, gives the range. For instance, they specify 102 to 120 degrees Fahrenheit on a 2011 Lexus IS350 with an A760E transmission. We check the same transmission in a 2011 Tundra, with a 4.6 liter engine, at 99 to 111 degrees Fahrenheit.

To tell the transmission fluid temperature, we can use a Toyota scan tool to read transmission temperature directly. This is easiest if we know the range needed. Fortunately, Toyota also provides an alternative method.

Toyota tool #09843-18040 to access temperature detection mode

Without the appropriate scan tool, we can use a jumper tool at the transmission diagnostic connector. Tool number #09843-18040 is available through Toyota and connects pin number four to pin number 13. When connected we start the vehicle and use the ‘D’ or drive indicator light to suggest transmission temperature. To use this method, we must enter temperature detection mode.

Using temperature detection mode

Jump terminals 4 and 13 to enter temperature detection mode

To access temperature detection mode, we connect tool number #09843-18040, between terminals four and 13.  Next we start the engine and allow it to idle. We should turn off electrical accessories, such as the air conditioning, radio and lights. Slowly moving the shift lever from park position, through all gears and back again, circulates the fluid.

To enter temperature detection mode we quickly shift between drive (D) and neutral (N), about once a second for six seconds. This will start the temperature detection mode. The drive (D) light will come on for about two seconds and then go off.

Allow the vehicle to idle and when the temperature reaches the proper range, the drive (D) light will come on again. With the engine idling, we can now remove the check-plug to verify the fluid level. If the D light starts to flash, we stop and let the transmission cool. A flashing light shows the temperature is too hot.

Fluid that is at the proper level will drip slowly from the check plug. No fluid dripping means we need to add until it does. We should allow A steady steam of fluid to drain until it barely drips.

An emergency ballpark fill-method

If we know the fluid level is correct before beginning, we might also catch and measure the amount drained. For instance when we service the transmission, we drain the pan and catch the fluid. We also need to account for any fluid that drains from the filter or valve body. Replacing fluid in the exact amount removed will put us in the ballpark, but is not as accurate as the preferred method. Fluid level should be correctly checked and adjusted when possible. This method will not work for a leaking transmission or where the original fluid level may be incorrect.

Finding the fill plug

Toyota type WS automatic transmission fluid

The location of the fill, check and drain plugs vary from one model to another. We check Toyota service data to find the plug locations. Other specifications, such as pan-bolt, drain and fill plug torque are also dependent on the vehicle model. Using the proper transmission fluid is also imperative. Most late model Toyota transmissions use world standard or WS. This is not compatible with Dexron or previous Toyota fluids and is not optional. Using the wrong fluid can cause shifting concerns and may damage the transmission.





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