The Toyota A750E was first
introduced in the 2003
4-Runner and Land Cruiser,
and the Lexus LX400 and GX470.
Since then it’s become quite popular,
showing up in the Tacoma, Sequoia
and Tundra in 2005 and the FJ Cruiser
in 2007.
These transmissions have been on
the road for up to seven years and are
getting a lot of miles on them. With all
the cars using this transmission, there’s
no doubt you’ll be seeing it in the years
to come (figure 1).
A common complaint is the trans-mission
falling out of gear when com-ing
to a stop, sometimes so harsh that
it feels like someone has rear-ended
you. This happens because the trans has
fallen out of gear due to low pressure,
caused by a faulty SLT pressure sole-noid.
The ECM then ramps up the pres-sure
to max and it slams back into gear.
Replace the SLT solenoid is the fix for
this concern. But before we get into
fixes let’s learn a little about this unit
Line Pressure
Specifications
Line pressure tap location and
specifications (figure 2).
ATF Temperature Sensor
This transmission uses two tem-perature
sensors, each with a different
function. The ECM uses ATF tempera-ture
sensor 1 to modify pressure control
for the clutches and brakes. If this sen-sor
fails, the ECM will prevent upshifts
into fifth gear and lockup. The ECM
uses ATF temperature sensor 2 for shift
timing control when ATF temperatures
are high.
In some vehicles equipped with the
A750E, the MIL may light intermittent-ly,
and the computer may store DTC
P2742 in memory (Transmission fluid
temperature sensor 2 circuit low).
To diagnose this, monitor ATF
temperature sensor 2 and watch for it
to short to ground intermittently. When
the sensor shorts, ATF temperature sen-sor
2 will indicate 302ºF (150ºC). This
is usually due to a faulty internal wiring
harness; replacing the harness will cor-rect
the problem.
ATF temperature sensor 2 has two
blue wires; ATF temperature sensor 1
has two orange wires (figure 3).
Solenoid ID and
Location
This chart provides
the repair manual ID
for each solenoid in the
A750E transmission,
and the part name and
description provided
in the electronic parts
catalog.
Figure 4 shows the solenoid ID and
location.
Valve Body Disassembly
There are a few procedures you
should always keep in mind when
working the A750E valve body. Two
things that you need to do are:
Make sure you record the
1.
accumulator control pressure setting
prior to removing the accumulator con-trol
valve (figure 5).
There’s no factory preset specifica-tion.
From the factory setting, you can
turn the stepper in to provide a firmer
shift feel. Backing the stepper out will
offer a softer shift feel.
Make sure you record the pri-2.
mary regulator valve setting before
removing primary regulator valve from
the valve body. The tallest step will pro-vide
the highest base pressure reading;
the shortest step will provide the lowest
base pressure reading (figure 6).
Always inspect the valves and
springs thoroughly during disassembly.
Check the valves for scoring and make
sure the valve bore is clean. Pay close
attention to the valve layout, and make
sure you put them back in the way they
came out.
Exploded View Upper
Valve Body 1
Install the checkball in the C3
check valve lineup (figure 7). If you
leave this checkball out, the transmis-sion
won’t go into reverse.
Always check the B1 accumulator
in the upper valve body (figure 8). This
is where debris will build up. It can be
difficult to remove, but it’s important
to take it out and clean the bore thor-oughly.Exploded
View Lower
Valve Body 1
The primary regulator valve and
the accumulator control valve are locat-ed
in the lower valve body (figure 9).
Record the settings for these valves.
Once you’ve recorded the settings, disassemble the lower valve
body, check the valves for scoring, and make sure the valve bore is
clean.
Always install the solenoid filter screen (figure 10) with the open
end up. The screen will snap into the separator plate when properly
installed. Install the torque converter check valve as shown.
Upper Valve Body 1 and 2 Checkballs
There are three sections to the
A750E/F valve body. Upper valve bod-ies
1 and 2 are the only valve bodies with
checkballs (figures 11 and 12).
All of the checkballs are composite.
Make sure the checkballs are in good
shape; replace any that are damaged or
have decomposed. All of the checkballs
are the same size: 0.217” (5.5mm).
The coast brake relay valve is locat-ed
in upper valve body 2 (figure 12). Be
sure to remove, clean and inspect this
valve body.
Lower Valve Body 1
The purpose of the pressure limit
checkball is to exhaust pressure if it
becomes too high (figure 13). The limit
valve will blow off at about 300 PSI.
Now that we’ve covered all sole-noids,
control valves and checkballs in
the valve body, reassembling the valve
body should be a snap.
The A750E valve body isn’t dif-ficult
to work with. But without the
proper information and understanding,
you could easily cause yourself problems
later on. That’s why it’s so important to
have all the information close at hand.
It’s not just smart… it’s Street Smart!
