Transmission for the 2JZ/MA7 hybrid conversion
As stated earlier there are a few options when selecting a transmission for
your 2JZ hybrid project. First of all you have the option of selecting a manual
and an automatic transmission.
I'll keep this story short, as I'm going with the automatic transmission and
I want to show you pictures! For the manual you can choose for the W58, the R154
and the V160. If you're getting the W58, you need the bellhousing off the 2JZ-GE
engine. If you're going with the R154 (standard Supra 5 speed) you need the
bellhousing of the 1JZ-GTE manual. If you're going with the Supra 6 speed, you
need too much custom work (making the tunnel bigger, fitting the rear diff.
Custom drive shaft etc.)
Depending on the available hardware and options, fitting the automatic transmission
can be 'easiest'. Easiest in this case means: Not much custom work and no big
investments in bellhousings etc. If you haven't bought your 2JZ engine with the
transmission, you need to buy the bellhousing anyways. I highly suggest to buy
the engine complete with automatic transmission, as the transmission is stronger
and the electric control is slightly different, although both transmissions are
'A340E'. Let's make a complete overview of what is exactly different.
The bellhousing for the 2JZ mates up to the JZ family of engines, while the
7M bellhousing fits the 7M. Easy modification; you just swap the bellhousing and
The left picture is the output shaft of the transmission from the 7M engine
and the right picture is the output shaft of the 2JZ-GTE engine. Note that the
normal aspirated engines of the 2JZ series have about the same type of
transmission as the 7M engines; these output shafts look the same and the
propeller shaft is of the 'slide in' type as well. Only the turbo models have
the upgrades transmissions with the 'bolt on' type propeller shaft. If you would
go with the output shaft in the right picture you would have to make a new
propeller shaft. This is not really difficult, but unnecessary. Furthermore,
there are more differences among the two output shafts. The shaft for the 7M
engine has two devices connected, one gear for the speedometer cable and one
'gear' for the rear ABS sensor. If we would go with the output shaft in the
right hand picture, we would loose these signals and had to made them ourselves!
The picture in the right hand side has two 'other' signals, that are used in the
JZ series. One connection is for the speedo signal sender, which is now an
electrical signal and one signal is for an additional speed sensor, used by the
ECT. This speed sensor is called 'Speed sensor No. 2'.
I would highly prefer the two signals from the 7M output shaft, over the
signals from the 2JZ shaft. The speedo signal can easily be extracted from the
No 1 speed sensor in the 7M dashboard. This speed sensor converts the speed from
the speedo cable to an electrical signal. Furthermore the ABS signal is very
handy if you want to keep the stock ABS system. I do, as I don't want to screw
around with the brakes and brake system too much. Somehow we have to 'fake' the
extra speed signal from the No 2. speed sensor. If you take a close look at the
sender for this signal in the next picture, you see it sends four 'pulses' every
revolation of the output shaft.
||The speed sensor no 2. sender mounted to the output shaft.
You can see that every revolation four little pieces of metal will pass
the speed sensor, resulting in four signals per revolation. It should not
be 'undoable' to get this type of signal out of the 7M rear ABS sensor or
the 7M stock speed sensor. Note that this signal is only for the ECT
As the output shaft is completely different, the extension housing is
different as well. I wouldn't care that much about the output shaft, but the
mounting points for the transmission to the body of the car are connected to the
extension housing as well, as shown in the next picture.
|Here you see the difference in extension housing. We don't
care that much about the extension housing, but the mounting points for
the transmission are quite different. The width of the mounting bracket is
substantially wider on the JZA8 body (Left bracket). It would be great to
use the extension housing of the MA7 body (right housing in the picture),
so the transmission bolts straight up to our MA7 body.
We've already discovered some slight difference in the electronics at the
output shaft (speed sensor etc.), but there is more difference among the two
transmissions. On the 2JZ transmission there is an extra speed sensor, measuring
the speed of the Overdrive direct clutch. This speed sensor is bolted into the
transmission almost at the front of the housing. It would be very handy if we
can use this speed sensor, as it is very hard to 'fake' this signal using some
other signals in the car. Another 'electric' difference is the neutral start
switch, mounted to the shift lever of the auto transmission (see picture).
||This is the neutral start switch and gear indicator from the
7M transmission. The JZ transmission switch is very much alike, although
more signals are given as output. While the M transmission has signals for
'P', 'R', 'N', '2' and 'L' the JZ transmission has all signals, including
'D'. As a detail we note that the connector is different as well.
- Control (Electronic Control)
A complete explanation of the auto transmission is currently beyond the scope
of this article, but to get a long story short: the automatic transmission is
controlled by 'pressures'. Normally you have 'line' pressure, 'throttle'
pressure and 'speed' pressure. At the 7M transmission, throttle pressure is
controlled by a manual throttle linkage. This is a cable you connect to the
throttle body, so the more 'gas' the more pressure in the transmission. Other
pressures are regulated in different manners. For gear selection the 7M
transmission uses 'solenoids'. These solenoids are used as actuators for
hydraulic valves to control shifting and lock-up timing. The M transmission has
three of these solenoids. One solenoid is used for 'Lock Ups' and with the other
two solenoids you can select one of the four gears (two on/off switches, four
The JZ transmission has the same amount of solenoids for the gear and lock-up
mechanism. These solenoids work in exactly the same manner as the M transmission.
However, the JZ transmission does not have a manual throttle linkage. Instead of
this mechanical way of regulating pressure, the JZ transmission has two extra
solenoids. The first solenoid is the "SLT" solenoid, regulating the
line pressure. The second solenoid is the "SLN" solenoid, regulating
the Accumulator pressure. It would be nice to adopt this new control unit in our
automatic transmission for the 2JZ project.
Yes people, I said clutches. Although most of us associate a clutch with a
manual transmission, the automatic transmission has clutches as well. And loads
of them! Furthermore there are brakes in the transmission also. These are used
for preventing various parts in the transmission from turning either clockwise
or counter clockwise. Let's make an overview on what is available in the
|O/D Direct Clutch (C0)
||Connects overdrive sun gear and overdrive carrier
|O/D Brake (B0)
||Prevents overdrive sun gear from turning either clockwise or
|O/D One-way clutch (F0)
||When transmission is being driven by engine, connects
overdrive sun gear and overdrive carrier
|Forward Clutch (C1)
||Connects input shaft and front planetary ring gear
|Direct Clutch (C2)
||Connects input shaft and front & rear planetary sun gear
|2nd Coast brake (B1)
||Prevents front & rear planetary sun gear from turning
either clockwise or counter clock wise.
|2nd Brake (B2)
||Prevents outer race of F1 from turning either clockwise or
counter clockwise, thus preventing front & rear planetary sun gear
from turning counterclockwise.
|1st & Reverse Brake (B3)
||Prevents rear planetary carrier from turning either
clockwise or counter clockwise
|No. 1 One way Clutch (F1)
||When B2 is operating, prevents front & rear planetary
sun gear from turning counter clockwise
|No. 2 One way Clutch (F2)
||Prevents rear planetary carrier from turning counter
As you can see in this table, only the Forward Clutch (C1) and Direct Clutch
(C2) both have one disc more in the 2JZ transmission. This will result in a
'stronger' transmission so whenever possible it's best to use these discs.
What we want to have is a transmission with the output shaft of the MA7, so
we can use the propeller shaft of our car, the ABS and speedo hookup. Then we
want most of the internals of the JZ transmission (preferably all) including the
speed sensor of the overdrive direct clutch. Then we use the control unit of the
JZ transmission as well, so that we have the five solenoids and the right
neutral start switch. Right? Well, LET'S START!!!
Step one. Getting the output shaft from the 7M transmission
||On the left you see a detailed component overview of the
A340E transmission from the 7M engine. If you click the image you can view
a full-size picture. The snap ring which is in front of the front
planetary gear holds the output shaft in the transmission. We need to get
to this snap ring by removing all parts that are in front. This starts
with the oil pump which is pictured in the lower left corner.
|I started with removing all electronics and the throttle
linkage cable from the transmission case. If you still have the bell housing
and extension housing on the transmission, you should remove
these as well.
||When you unbolt the oil pan, make sure you don't turn it
over, preventing all the foreign material in the bottom of the pan from swimming
around your transmission. There is quite some junk in the pan and you
don't want that to go to the transmission. Removing the pan is done by
unbolting all the little bolts and then cutting the gasket material with
some sharp knife.
|When the pan is removed from the transmission you can unbolt
the three bolts holding the oil strainer to the valve body.
||These two tubes connect the valve body with the pressure
plates for some gears and clutches. Use a big screwdriver to pry them out
carefully and remove them.
|After disconnecting the three wires that control the
shifting and lockup solenoids, and getting rid of the manual throttle
linkage, you can remove the valve body from the transmission. Removing is
done by unbolting the 17 bolts that hold the valve body to the
transmission. Do this in a couple of turns as the valve body is under
pressure from springs underneath it.
||Gently remove the check ball body (with the little ball on
top) and the spring.
|On top of the C0 accumulator piston (the one piston alone,
not grouped with the three others) are two springs. Remove these.
||Normally you can just remove the B2 accumulator piston as
one piece. There is one spring underneath it. If you cannot remove the
piston, you possibly need some compressed air or try to take the piston
out in parts.
|Removing the other pistons is quite the same procedure. When
you are complete you should have the same parts laying on your desk as in
this picture on the right. On the top left are the two springs from the
C0, then you see the B0 piston with it's one spring. The next two pistons
are C2 and B2.
||When you remove the seven bolts holding the oil pump into
the transmission, you find two holes with extra thread tapped in. Use two
bigger bolts to screw into these holes and gently push out the oil pump by
screwing these big bolts completely in. Use even passes for the bolts so
the oil pump comes out straight (and not diagonal or something).
If you are so fortunate to have the special puller from Toyota available
(SST 09350-30020 or 09350-07020) you can use this one.
|If you pull the input shaft, the overdrive planetary gear
unit with the overdrive direct clutch, one way clutch and the overdrive
planetary ring gear will come out as one big assembly.
||Remove the overdrive planetary ring gear from the overdrive
planetary gear. Take special care for the bearing and races between the
two. If you've laid everything aside, we can continue with removing the
overdrive brake pack.
|The overdrive brake consists of a couple of clutch plates
which are kept in the transmission body by a snap ring. You can remove
this snap ring by using a screwdriver (gently please).
||You can remove the overdrive brake disks as one assembly
now. The assembly consists of a flange, five plates and four discs and
|On the side of the transmission is a snap ring holding the
second cost brake cover in. Remove this ring. It is very likely the cover
will not come out yet.
||Getting the cover off the transmission when the snap ring is
removed is easy. Just blow some compressed air into the oil hole and
remove the brake cover, piston assembly and spring.
|Here you see the whole coast brake assembly. The spring, the
piston (with a rod), the dust cover and the snap ring.
||Continuing with the transmission internals, we are going to
remove the overdrive support assembly. First remove the bearing with the
race which might still be in the transmission (it's possible it came off
with the last removal, check that as well).
|The overdrive support assembly is bolted into the
transmission with two little bolts. Remove these two.
||When you remove the big snap ring (special tool needed, big
snap ring wrench), you can pull out the overdrive support assembly using
the same methodology as used for the oil pump. Just use two bolts and
press it out gently.
|Now pull the little shaft inside the transmission. You will
take out the direct clutch and the forward clutch as one piece. Take extra
care for the bearings and races.
||At the arrow is a little E-ring. You can remove this with a
small screwdriver. After removal you can gently pull out the pin. When the
pin is removed you can remove the brake band through the big hole in the
transmission (front side).
|Pull out the front planetary ring gear from the case. Again,
mind the bearings and races that might be on / in.
||Take out the last race that's laying on / sticking to the
front planetary gear unit.
|Now go into the transmission and find a little snap ring
holding the output shaft in the transmission. Get your snap ring wrench on
the ring and remove it. This is very difficult, but after a couple of
tries you will succeed (when you got the right tools). Note; picture might
not be exactly as the transmission. I took this while experimenting with
two transmissions at the same time.
||When the little snap ring is removed you can take out the
front planetary gear.
|Now pull out the planetary sun gear with no. 1 one way
||Now you can pull out the 7M output shaft (from the rear).
This is the base of our transmission!
|Consider yourself half way of the hybrid
conversion. Now let's disassemble the A340E transmission of the 2JZ. As
the transmission is about the same in design, I'm only showing the real
|The valve body of the 2JZ transmission looks substantially
different than the one from the M transmission. This valve body contains
the 5 solenoids and some other control stuff. Remove it carefully. No oil
pipes are attached. The body is very big.
||In the Japanese mkIV transmission I found this little
'dampener' at the first discs (the O/D discs). This little device was not
present in my mkIII transmission.
|One note on pulling the output shaft from the
mkIV transmission; my transmission had the bolt at the end screwed up so I
was unable to remove the extension housing from the transmission. I ended
up pulling the extension housing with output shaft together. Not a bad
So let's build our hybrid transmission. You have two transmissions in
parts laying on the work bench, so let's start quickly. We take the A340E
of the 2JZ engine as a base. There are still some parts in. First we
should compare these with those of the M engine, to make sure we don't
have any differences or so.
The parts that are inside the transmission are:
- Rear planetary gear. This gear is the same in both transmissions
(assuming both transmissions are from the turbo cars), so we can have
this one in place
- No 2. one way clutch. This clutch is the same in both transmissions.
So no change necessary.
- 1st & rev. brake pack. These clutch plates are slightly
different, but as the unit is one assembly we can keep it all in the
transmission. These clutches don't interfere with the newly installed
output shaft either, so no need to go back to original. Both
transmissions contain 7 clutch disks here.
- Second brake Drum. Another part which is exactly the same on both
transmissions! Keep it there.
- Second brake pack. I cannot trace if these are different among the
two transmissions, but as the rest is the same, we can keep these
disks from the 2JZ without any problem!
So first throw in the No. 1 one-way clutch, which came out of the
transmission together with the planetary sun gear. Both these items are
the same on the transmissions (although the 2JZ got a redesign after may
94). To be sure, just drop in the unit from the 2JZ. If you can't make the
unit in the transmission, you have to remove the complete brake pack, but
I wouldn't do so. (well, I did, but if I had to do it again, I would NOT).
|Now you can install the planetary sun gear. Again, these
units are EXACTLY the same on both transmissions. At first glance, I
thought they were different but that was just a slight detail. The
electronic parts catalog mentions both units have the same number.
||Now gently slide in the output shaft of the 7M transmission
and stand the transmission on this output shaft. I used a small table to
stand it on.
|Now things get tricky! As you can see in the picture on the
right, the front planetary gear units are not the same. The left unit is
from the 7M transmission and the right unit is from the JZ transmission.
As this unit mounts to the output shaft, we need to make use of the M
unit. The M unit comes with it's own bearings and races so use these as
well. Mount the unit in the transmission.
||Now put the snap ring on the output shaft. Quite a difficult
work this is, but trust me: Getting it off is more difficult than putting
it on! Don't forget the race on top of the planetary gear assembly!
|Now we have to create a unit which needs to be mounted all
together inside the transmission. The problem we're facing here is that
the unit needs to be mounted on the 7M front planetary gear unit. As these
units are different we cannot use the unit for the JZ, so we are stuck
with the 7M unit. The unit I'm talking about is the front planetary ring
gear, highlighted in this picture.
||The next 'problem' we're having; as the front planetary ring
gears have different dimensions, is we need to make use of the forward
clutch for the 7M as well! Ahh, that's a pity as the JZ engines come with
a forward clutch with 7 discs, while the M engines are equipped with 6
discs. I haven't found a solution to install the 7 discs yet, but with
some custom work on the size of the flange you can get quite far. But I
wanted to get my car driving BEFORE CHRISTMAS, so I decided to put in the
6 clutches. I did replace them with the JZ clutch discs, as my M engine
was completely worn out because of the previous abuse (400+ bhp). The
clutch discs have different order numbers so I currently don't know if the
replacement of the discs was a good idea! Otherwise I need to go back to
new M clutch discs.
|Now there was some good news. This assembly does fit the
direct clutch drum of the 2JZ. So we can use the direct clutch discs out
of the 2JZ transmission, resulting in one disk more than the M
transmission! These discs did look most worn in my transmission, so very
important to upgrade! The picture shows the complete assembly to be put
into the transmission.
|Getting the assembly into the transmission is
quite easy. You need to keep the transmission case with the big opening
facing downwards. Then you can put the assembly into the case. This is
different than what we did before, when we put everything from top into
the case. Before you can install the assembly, you need to put the second
coast brake band in. These are different in the two transmissions, so I
have put the JZ band in.
||When you have installed the assembly inside the
transmission, you can turn the transmission over again and install the
rest. This includes the second coast brake piston, the overdrive support
assembly, all other O/D related parts, the oil pump and the valve body.
|This should be the result. A complete hybrid transmission
with the output shaft of the M engine and only the number of forward
clutch plates being the same as in the M engine. The rest is all from the
JZ engine. Let's hope it works!!!! Otherwise we have to take the
transmission apart again.