Replacing an auto gearbox

Buying a replacement box to fit your gto is not as straight forward as going by just the year of the
car alone…

Firstly the box has a number stamped on it which needs to match the replacement box… BUT
it doesn’t end there as there are different variations within the boxes that all have the same part /
box number…

Once getting the correct box number you then need to check where the bigger of the two wiring
looms connects the box to your car loom…

one box will have just a plug where your car wiring loom plugs directly into the box next to
where the gear selector arm enters the box itself

another may have a short wiring loom coming from just beneath the gear selector lever on the
box and connects to the car wiring loom further over next to the car battery…

Buy the wrong one and you could find that your car wiring loom finishes just by the battery and
doesn’t reach the plug a good foot away on the gearbox selector lever socket

There is also two different ways in which the oil temperature wire goes to the gearbox ( The
single Blue wire ) that is a separate wire on it’s own and not wrapped within the main loom.
although this is a simple conversion to make either type of temperature wire fit.

However… if you have both types of box in your hands ie… the one in the car and a replacement
one but even thought both will have exactly the same box / part number it is possible with a bit
on mechanical know-how to make one good box that will fit out of the two…

You will find the box number just below the thermostat on top of the bell housing and this is the
first bit of info you will need to have and will get to it easier by unclipping the air filter box lid
and moving it to one side if it still has the original air filter fitted. :wink:

Just another thought… and may or may not be or any use…

It could also be handy to know what type of TCU is fitted to the car… the TCU is much like the
Engine ECU but the TCU runs the auto box…

On the gearbox your in need of there are two different types of TCU’s fitted to the car… I know
this because I have 2 gto’s both using the exact same gearbox but both having different TCU’s
fitted to the car…

Forgetting the TCU part / id numbers they are easily seen without having to remove the TCU
from out the car but removing the drivers side carpet panel on the side of the center consul and
looking behind the stereo… The engine ECU is fitted upright behind the stereo and the gearbox
TCU is the one laying flat on the floor…

One type has 3 loom plugs that plug into the TCU and the other has only 2 plugs… both have a
slightly different wiring setup going to them and use different pins that the wires go to…

The reason I’m saying this is because the 3 plug TCU uses a low oil temperature sensor as well
as a high temperature sensor… the 2 plug TCU uses ONLY a high temperature sensor and No
low temperature reading…

This is only theory at this moment as another cub member and myself are still in the middle of
trying to create a patch lead that will convert both types of TCU’s to fit both types of wiring
looms in a gto and is just a thought that is in my mind at this moment is…

If fitting a gearbox which has a low temperature reading sensor inside it and is normally
connected to a 3 plug TCU… But is connected to a 2 plug TCU that doesn’t have the ability to
read a low temperature reading then it should make no difference as it wont be looking for a low
temperature reading …

But if fitting a gearbox that doesn’t have low temperature reading sensor inside it and is
normally connected to a 2 plug TCU… But is connected to a 3 plug TCU that can read and look
for low temperature reading… whether when turning the IGN on the gearbox TCU does like the
engine ECU and check itself and if so whether it not receiving any signal from the low
temperature sensor as it now has a gearbox fitted that doesn’t have a low temperature sensor
fitted inside it, whether it may or may not cause it to throw up a fault.

As said before I have 2 gto’s both using what look to be identical gearboxes including the way in
which they both connect to the main car wiring loom… but both use a different 2 and 3 plug TCU
to run them… it’s just a thought thats worth keeping in mind as a 3 plug TCU is gold dust and
taken me over a year to get a replacement where as the 2 plug TCU is much easier to obtain

The impression is that the gear box that has the car main wiring loom that reaches the gearbox
and plugs into the socket directly next to the gear selection lever as it enters the box appears to
be the most likeliest one of the two boxes that has the low temperature sensor fitted in it and is
probably not being used or looked for by the TCU on my gto that has the same gearbox fitted but
using the 2 plug TCU that doesn’t have the ability to read a low temperature reading :wink:

Interesting stuff… just me then :rofl: