Holden Adventra 6 Speed conversion

This page outlines the conversion process to install a Tremec TR6060 6 speed manual gearbox into a Holden Adventra all wheel drive.

The following are the Holden V8 VY & VZ cars from 04' & 05' suited to this conversion.

Holden Adventra CX8
Holden Adventra LX8
Holden HSV Avalanche
Holden crewman Cross 8
Coupe 4

WARNING: Fitting a six speed manual gearbox to your Holden Adventra is going to wake your car up !
Your Adventra will now have more get up & go & a gear for EVERY situation.
It will put a never ending smile on your face & every time you see your car parked in the driveway you simply cannot resist taking it for another drive...................because it's so much fun.


Photos on this page show the conversion of an Adventra CX8.
All V8 cars in the above listing will be exactly the same as they all use the same NV124 transfer case.
For V6 cars they also use the same NV124 transfer case, but an adapter plate between the TR6060 bellhousing & the V6 engine would be required.

NOTE: You will need to have good mechanical skills to perform this work.
Some fabrication work is required to modify the transmission cross-member & grinding work on the C5 tail housing.
There will be small problems to solve along the way.
This outline is a guide only & not a definitive step by step every nut & bolt type framework.
General mechanical fitment of parts is not covered here, it is presumed you have those skills.

The kitset for purchase is listed at the bottom of this page.

The picture above shows from left to right the whole assembly on the bench.
(these components were setup on the bench to work out the conversion).

LS1 sump pan with differential.
LS1 Tremec bellhousing
Tremec TR6060 6 speed transmission
Corvette C5 Tremec trailhousing
Conversion housing
NV124 transfer case


When converting your own car this is what you will need to do, build up the gearbox & transfer case assembly on the bench.
Except you don't need to set up the sump & the front differential, those parts can stay in the car.

The assembly ends up approx 47mm longer than the factory setup.
Which means the front section of the rear prop-shaft will need to be shortened by 47mm & the front prop-shaft lengthened by 47mm.

You need to purchase one of these.
Tremec TR6060 6 speed transmission from a VE Commodore.

You will need to remove the output flange & the tail housing as pictured above.


This picture above shows the Corvette C5 Tremec tail housing fitted to the TR6060 gearbox.
The reason why this housing is used is the convenience of having a flange face to bolt the conversion housing onto.
The original TR6060 gearbox has a standard tail housing which has no suitable areas to bolt adapters onto.

This picture is the Corvette C5 tail housing.
AC DELCO Part number 19206298.
It's sometimes listed as an "Automatic transmission case rear extension"
Ignore that reference, This part number is a manual transmission rear extension as used on the Corvette C5 fitted with a TR6060 transmission.
You can see from the above image it has two studs sticking out of the case, these need to be removed.
Also it has as part of the casting two wings sticking out the left side.
The lower wing needs to be removed as it simply gets in the way.
This wing can be carefully cut off using a 5" grinder with a 1mm cutting disc fitted.

A handy tip here is to apply wax, (candle wax etc) to the cutting disc sides.
This prevents the cutting disc from clogging with aluminium.

After cutting off the wing, sand with a flap disc on the grinder to blend the casting.
Do this work to the case before fitting to the transmission.

You can see here where the wing used to be & how the finish face has been cleaned up, (circled in red).

This picture shows a small red area that needs to be ground in the top of the C5 tail housing.
This small recess in the case allows added clearance for the gearshift push rod which passes over the top of the gearbox assembly.
The recess needs to be around 10mm deep.

This image above shows the male threaded spigot on the end of the Tremec gearbox removed, (circled in red).
It can be carefully cut off, again using a 5" grinder with a 1mm cutting disc.
DO NOT cut into the spline.
It's best to cut off the threaded section & leave a tiny amount still on the shaft.
Then finish blend the end of the shaft with a flap disc.
Be sure to cover up any exposed areas of the transmission to avoid cutting dust contamination.

The inside of the C5 tail housing needs to have all of the internal parts transferred over from your Tremec TR6060 tail housing & fitted into the C5 housing.
MAKE SURE IT'S CLEAN !

The TR6060 Tail housing has installed what is called a Reverse lockout solenoid.
The reverse lockout solenoid is there to prevent accidental selection of reverse gear in the 6 speed transmissions when shifting from 4th to 5th gear.

The C5 tail housing does not have provision for this lockout solenoid.
On my installation I retrofitted this lockout solenoid to the shifter mechanism.
And it works really well. It's not wired in, it just relies on the plunger spring pressure.
So it takes a little more effort to select reverse to overcome the spring pressure, but still easy enough to select.

The grey coloured bracket has been fabricated to use as a mount for an aftermarket VE short shifter & also houses the lockout solenoid.
There are aftermarket lockout solenoids that are really just a spring with a plunger, (no actual solenoid). Which is better suited to the above installation as the aftermarket units are more compact & take up less room.
I ended up fitting the item below as it's more compact & easier to install.
As pictured below.

A quick note here on shifters.
I used the original VE shifter push-rod, (has a forked type clevis on each end).
And as you can see in the above photos I made a steel bracket to hold an aftermarket VE type shifter onto the top of the transfer case.
But the bracket I made is likely not required.
The original VE push-rod was used & the shifter ended up exactly in the right position.
That indicates you could use the original VE shifter mechanism.
You would need to make mounts to attach it to the transmission.

Above picture is a standard VE shifter.

When removing the original TR6060 tail housing there is a shaft that is attached to the rear of the internal shift shaft.
It's held in place by a 3/16" roll-pin.
Tap out the roll-pin with a pin punch & remove the shaft.

The shaft looks like this, (above).
It's no longer required as this is what engaged the reverse lockout solenoid & it will not fit into the C5 tail housing.

When you have installed all of the internal parts from the original tail housing into the new "modified" C5 tail housing you are ready to install it onto the TR6060 gearbox.
Make sure it's all clean & free of old gasket compound.
An issue with installation is the TR6060 shaft has a fairly large snap ring groove & this can interfere with the output seals in the C5 tail housing.
The seal has to 'hop over' the snap ring groove.
The seals get hung up on the groove & you will damage the seals if you persist with trying to put on the case with force.
What I did was first remove the seals from the case.
Install the case & then fit the seals from the outside.
You still need to be really careful with that snap ring groove as the seal lip wants to drop into the groove.
Use a good quality RTV based gasket compound on the case join.
RTV compound is what the cases originally had as a sealant.

Now you can install the adapter shaft as pictured above.
It should be a fairly firm fit on the spline.
Make sure the spline is clean & free of any damage or burrs.
The end of the adapter shaft, the male spline has a groove for the original snap ring.
The snap ring is part of the original adapter shaft.
I didn't bother fitting the snap ring as when the shaft is installed it can't really float forward or backward.
But it's there if you want it to fit up like the original.

Now the adapter housing fits in place.
Again use RTV gasket compound between the C5 tail housing & the adapter housing.
Bolt up with M10 bolts, flat washers & nyloc nuts.

Pictured above is the Adapter housing.

You can now fit the transfer case that you have removed from your car.
On two of the bolt locations there are tube type location dowels.
Re-use these dowels on the oversize holes between the transfer case & the adapter housing.
The dowels normally stay in the transfer case anyway.
Clean the contact face, again make sure it's free of gasket compound.
Re-apply fresh RTV type compound & bolt together using M10 bolts, flat washers & nyloc nuts.

You should now have something that looks like the picture above.

Remove the speedometer sensor from the side of your original gearbox.
It is held in place with one bolt.
The steel mounting tag needs to be removed from the sensor.

To remove the mounting tag, gently bend the tags apart, tags shown in the above picture & the arrows show the direction the tags need to be moved.
To do this you can clamp the steel mount in a vice & use a flat blade screwdriver to tap the tags apart.

The sensor can now be fitted to the Adapter housing.
First batch of housings ( 01/01/24).
Remove the original O-Ring on the sensor & when installing use a small amount of RTV gasket compound around the underside of the sensor head.
There is no oil in this part of the housing.
The RTV is just to keep moisture out.
The sensor requires fitting with the new stainless clamp supplied with the kit & the M5x12 capscrew.
NOTE: The second batch of housings, (from 25/09/24) uses the original O-Ring on the sensor, no need for RTV compound in this area.

Now you need to look at the clutch slave cylinder.
It's worthwhile installing a new one as once the gearbox is in place the only way to change the slave cylinder is pull the gearbox out again.

You need to install the flywheel & clutch to the motor.
The clutch you use depends on the year of your gearbox.
And you need to install the correct spigot bearing into the end of the crankshaft that suits your gearbox shaft.

 You may want to change the oils in the gearbox & transfer case at this stage as it's easier to do on the bench before fitting the whole assembly to the car.

Pictured above is the original automatic shift lever & cable.
This needs to be removed from the car.
The shift lever comes out from above & first requires the plastic centre consol to be removed from inside the car.
The alloy casting of the shift lever has four M8 nuts that hold it in place, which are up under the car, inside the tunnel.
These nuts can only be easily accessed once the Automatic transmission has been removed.
The cable mount also need to be removed which are a further two nuts under the tunnel, the bracket is pictured above circled red.
Now, because Holden made these nuts so inaccessible when the transmission is in place I did not want to have dramas with future access to this area.
So up under the car within the tunnel I welded in 6 x M8 plain nuts.
I held the nuts in place with six M8 x 16 bolts passed through from above.
Then under the car & put three short welds on each nut to fix in place, then remove the bolts.
This means that attaching anything from above to these holes now just requires bolts screwed in from above.
There is a hole in the tunnel that allowed the original shift cable to pass through.
The red circled bracket in the above picture bolted into this area & covered the hole along with it's rubber gasket.
This hole needs to be plugged up to stop fumes entering the car.
So, make a plate from 3mm steel to cover the hole & bolt in place from above with a liberal mount of silicone sealant to seal up the hole.
The plate bolts down to two of the M8 nuts you have just welded in.

Shift cable cover plate drawing above.

The standard transmission cross-member needs to be modified.
This is because the transfer case sits further rearward than stock, about 47mm.
The major modification is to cut a section out of the front of the cross-member for transfer case clearance.

The whole transmission/transfer case assembly sits about 30mm lower than standard at the transfer case.
This is so that wing on the right side of the C5 tail housing does not hit the inside of the tunnel.

The cross-member has a 35mm deep long notch cut out of it to clear the back of the back of the transfer case.

You can see the modified cross-member in the above photo painted grey.

The easiest way is to support the transmission is with a transmission lifter.
Then bolt the cross-member in place with some over-length M10 bolts into the chassis rails.
Now looking straight up you can see what area of the cross-member will foul on the rear of the transfer case.
Use a marker pen mark on the cross-member to determine the section you need to cut out.
Cut the cross-member with a 5" grinder with 1mm cutting blade.
This exposes the hollow inside of the cross-member so then you re-box in across the front exposed cut face using 40x6 flatbar, fully welded in.

A spigot welded into that notch area that picks up the original transfer case rubber mount.
The Spigot is made from 25mm diameter solid bar with an M12 thread through the centre for the mount bolt.

You can see two other brackets that I made in the above photo.
The top one is the steel ring bracket that was originally on the back of the transfer case.
I have welded that bracket to the top of the gearbox mount from the TR6060 transmission. (this mount was on the bottom of the TR6060 original tail housing).
You can see two holes in the top of the cross-member.
This new mount bolts down to the cross-member & the ring mount onto the back of the transfer case again.
It may be overkill & not required but I decided to install this extra mount.

When you removed the transfer case from your car it would have had the above alloy transfer case mount attached to it, (pictured above).
I didn't bother using this part as it's so big & bulky & gets in the way.

The other bracket picks up the three threaded holes in the bottom of the chassis rail & the opposite side of the original transfer case rubber mount.

Also, there are other parts you are going to need to install.
Get yourself a pedal set, brake & clutch pedal from a VZ manual Commodore.
You will need to remove the original brake pedal & install the new pedal set.
You will need to reconnect the brake light switch & cruise control switch on the brake pedal.

You will also need a VY or VZ clutch master cylinder & reservoir.
As well as a clutch hose that goes between the master cylinder & gearbox slave cylinder.
All of the mounting points for these items are in the car.
I'm not going to get into how to install them as it's basic mechanical work.

Prop-shafts.
Front prop-shaft needs to be made longer by 57mm.
Rear prop-shaft needs to be made shorter by 57mm.
You may need to get a driveshaft repair/balancing company do this work for you.

When re-installing the rear prop-shaft it would be a good idea to replace the rubber donut on the back of the transfer case.
Be careful with the M12 nuts that hold the donut to the output flange & the M12 nuts that hold the donut to the prop-shaft.
The three nuts on the output flange studs are M12 metric fine.
Where as the three M12 nuts that hold the donut to the Prop-shaft are M12 coarse.
The nuts outwardly look the same, DON'T GET THEM MIXED UP !

Because the transfer case sits lower by around 30mm I fitted some 30mm spacers between the chassis & the rear prop-shaft support bearing mounts.
So the rear prop-shaft was sitting at the correct height.

In the above picture the spacers can be seen made out of 30mm diameter Aluminium round bar.

Once you have the shifter installed it's going to require a cover boot to seal off the underside of the car to prevent fumes entering the cars interior.
This is not to be confused with the leather boot under the shift knob of the cars interior.

Above is pictured a VY or VZ Holden manual transmission shift boot.
These items can easily be purchased online.
This is installed from above & uses a custom clamp flange to hold down in position.

Above is a drawing of the shift boot clamp flange.
This bolts down to the 4 x M8 nuts welded into the underside of the tunnel.

There are a few minor jobs that need to be done with the wiring.
The engine will not start as the ECU expects the Automatic transmission to be in park.
To solve this issue I unbolted the selector switch from the side of the Automatic transmission, put it in the park position & simply plugged into the original wiring socket & cable tied in place.
If you have better wiring diagnosis skills than I do you may be able to figure out which wires need to be bridged to solve the problem in a tidier manner.

The reverse switch on the TR6060 6 speed needs to be connected.
To do this you need to first obtain the correct electrical plug to plug into the right side of the transmission.
The reverse switch is simply two wires.
On the rectangular plug that plugged into the Auto transmission you need to cut away two of the wires.
Wires:
Brown/Blue
Light Green
Instead of these wires going into the Auto plug, take these wires to the reverse switch plug.
Then you have reverse lights.

When installing the new pedal set you need to re-connect the brake light switch as well as the cruise control switch.
The wiring on the cruise control switch needs to be bridged over to the clutch pedal switch.
This is so if you depress the clutch pedal it cuts out cruise control.

The cable, (two wires) that connects to the speedo sensor needs to be extended to reach the new position of the speedo sensor.

A list of required parts for the conversion:
1 x Tremec TR6060 VE Commodore six speed transmission.
1 x Tremec LS1 Bellhousing, (sometimes comes with transmission).
1 x LS1 flywheel.
1 x LS1 clutch.
1 x Crank spigot bearing.
1 x Adapter kit, (Housing & shaft).
1 x Corvette C5 tail housing, AC Delco part 19206298.
1 x VZ Commodore manual Brake & Clutch pedal set.
1 x VZ Clutch master cylinder & reservoir.
1 x Clutch hydraulic hose, (from Master cylinder to slave cylinder).
1 x VE type shift lever
1 x VE shift pushrod
1 x VZ manual internal shift boot.
1 x Boot clamp flange.
1 x Tremec reverse switch plug.

First impressions driving the Adventra with the six speed manual.
Friggin WOW !
Why did not Holden make this a standard feature?

After a few seconds the dash will come up with an audible engine warning.
Hitting the "mode" button gets rid of that, but a small icon will remain.
The dash will also display the Auto is in second gear.
Yeah I know you don't have an Auto anymore, it's just the ECU is a bit confused.
Apparently re-flashing the ECU & telling the ECU it's now a manual will get rid of those hiccups.
But as of writing this, 12 weeks in, it's doesn't bother me & it's not a priority.
Something I will do later.
Cross Trac & ABS still work perfectly.
The car is also a great deal more economical on fuel.
It will cruise along in 6th gear from 60 kph right up to 110 kph + without having to change gear, (on flat ground).
Cruising on the highway at 90 kph I'm getting 10.5 litres per 100 k's, sometimes much better.
Around town it hovers around 11.5 litres.
But that's only after you have been driving it several weeks & the excitement has worn off a little & you're now driving a little more responsibly !
(yeah right!).
Economy will depend on your tyre size as well, as tyre diameter effects gearing.
I'm running 235/60-17 Goodyears, (714mm overall diameter).
714mm is the absolute maximum diameter you can fit at standard ride height & they occasionally just touch the front inner guards on extreme lock.
After driving it now for 12 weeks I still get an absolute buzz out of driving it.
And I know I will do for many years to come.
Without needing a transmission rebuild every so often, like the old 4L60E.

Any questions can be emailed to the following address:
tony@theedgeproducts.com