Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.
I was motivated to do the conversion because I love the car but the gearbox has always been a weakness. Most people who I discussed it with either just laugh or told me I was crazy and wasting my time and money. In the end the car was off the road for 6 months, it cost a little more than I initially expected but the results are totally worth the time and effort it took.
I had a great opportunity to undertake this project while studying, I am an engineering student so I have accesses to some cool toys and am working with some very skilled and knowledgeable people. I had lots of help along the way, a massive thank you has to go to all my friends who helped out, you know who you are and you know how grateful I am for your help.
I bought my Adventra LX8 sight unseen from a bloke in Perth (I live near Sydney). I fell in love with the car on the internet and had to have it. It has all the usual mods for these cars with a few fun extras which made it irresistible.
Multi-point injection LPG system, so cheap to run. Pacemaker extractors, into an Xforce exhaust. OTR and maffless setup. A 40mm suspension lift, with Pollyair bags in the rear and smaller 16” VE wheels, at the time I bought it had cooper discovery tyres on it.
Despite waiting 6 weeks for the car to come over from Perth, thanks to a transport company that went into liquidation, I fell in love immediately. Unfortunately not long after the gearbox started playing up. For ages it would struggle to decide between 2nd and 3rd. Then a couple of times it just started slipping in 3rd. Eventually the gearbox let go completely and only first and second gear worked, some of the time. That weekend I had a mate over and we decided to pull the gearbox out.
I had already looked into getting the auto rebuilt and decided that that was not a long term solution. The choice was then do I want to stick with an auto and get a beefier one or go for the manual option. After discovering that the larger auto was only really available from the states and was going to cost lots of money and not fit very well the choice became clear. Manual was the way to go.
First trip was to a wreckers to check out the physical size of the manual box, I first measured a T56 from an YV SS, but just happened to notice a complete motor and gearbox package from a VE which had a TR-6060 box on the back. The TR-6060 is around 100mm shorter in length than the T-56 so I decided that would be the easier one to work with given space as going to be at a premium.
After finding a conversion package with a t56 box and then somehow finding someone to swap the T56 with who had a tr-6060 I had all the parts I could buy. So it was off to my mates workshop to start the fabrication.
You can see in the photo that the manual is a fair bit longer than the auto, there other issue is that the spline on the TR-6060 does not match the 4l60e/t56 pattern.
I also took the opportunity to inspect and service the transfer case while it was out.
The first part of the build was to manufacture the drive line components. This meant custom shafts between the gearbox output and transfer case input. The standard auto setup uses a small adapter shaft that has a female to male spline adapter. It also has the speed sensor on it, so this had to be moved. My first idea was to modify the input shaft of the transfer case to fit the spline from the gearbox output. The issues with this idea was getting the parts within a close enough tolerance and because the output of the TR-6060 is not a slip yoke this proved impossible. This meant that he system had no tolerance for misalignment. My second and sucsessful solution was to use the male section of the original adaptor shaft to go into the input shaft of the transfer case. A tripod plates was CNC Plasma cut, milled and welded to this shaft to create half of the linkage. The other half of the linkage was a modified version of the original TR-6060 output yoke. Both of these plates where joined with a rubber couple.
Getting in the expert from some precision welding
Finished couple
Now that the drive line parts were done it was time to start making brackets to hold everything together. The hardest part was working out the geometry of everything and trying to keep it all aligned. Luckily I had some help from my little mate ROMER, the CMM machine. CMM or coordinate measuring machine is a tool that measures 3d objects and translates the points into computer software. Also made some models of the cross member for later use when fabricating the custom one.
With a lot of help from my mate we modeled the entire gearbox and transfer case interface.
From there it was simply a case of drawing a bracket in cad that fit between the two.
I then got the parts CNC plasma cut and welded it all together. The bracket uses the existing mounting points on the bottom of the box, as well as relying on the strength of the rear of the housing. The shifter mount points were used to support the bracket but hey take very little force. I also fabricated a new shifter mount, as the old one did not fit.
Here is a mock-up of the bracket on the box.
And the finished product, always nice when it looks something like the model.
After a quick test fit it was obvious that no amount of modification was going to get the original cross member to work, so a need one was designed base on the geometry of the original one and using the same mounting points.
The earlier CMM work really paid off.
After the cross member was done and everything was mounted I got a new set of tail shafts made up, as the old ones did not fit with the new transfer case position.
While I was waiting for the shafts I started work on the electronics. I had the PCM reprogramed with a manual tune, also opted for the 300KW option while I was at it. I chose not to swap the looms as my gas system is integrated into the auto loom and it would have been a lot of work to move it over to the new loom. So instead I swapped a few pins around and got all the wires needed to run the manual out of the auto loom. The only thing I had to add was a relay on the clutch switch so that is kill the cruise and also closes the auto inhibitor switch/clutch switch so the car can only start with the clutch in.
Mounting the shifter turned out to be a little tricky and required a few custom brackets and mounts. Also the original shifter just rubbed the top of the transfer case so I installed a short shifter kit, so that the lower section of the arm was shorter.
The first drive was interesting, I was a little worried down the driveway as it seemed to be labouring and the clutch seemed very heavy, I was in 3rd. This only became apparent when I floored it out of the driveway. So you can take off in 3rd, I just wouldn’t recommend it. However with a few adjustments of the shifter I managed to find 1st instead of 3rd and the relief was real.
The car had spent 6 months in the drive and was filthy and due for rego, so it was off to the engineer for a certificate and then to the mechanic but bath time first.
I think it was one of the very few pink slips that saw the car go up on the hoist, the boys at my mechanic all needed to have a look, I didn’t mind it gave me a good chance to get some photos. I also realise just how much easier this would have been with a hoist!
The build has been really fun, but the best part is having the car back on the road after so long. There are a few small issues that I still need to sort out, but all in all I am very happy with the result. All up it cost me around $5,000 but that was with lots of favours from mates and many hours of mine and their time.
I have now been driving the car as a manual for about 6 months and the system has done 5000km without any major issues. The biggest change apart from the fun of having the manual is the economy and performance. The cars 0-100kph time has gone from 6.9 to 6.2, there is definitely room for improvement too (I need to learn to launch it), yet to run it down the ¼ but I will update when I get a chance.
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The economy is now much better as well, I am getting 11L/100km on long freeway trips and that’s on LPG, sits just under 2000rpm at 110kph, in 6th.
So what is the future of the project, I would like to get it to a stage where I can sell it as a kit, but that will require a fair bit more development. I am not ruling it out, but at this stage I don’t have the time or money to do what is required, so for now I’m just going to enjoy driving the car.
Hey mate unfortunately the pictures are not working but sincere respect for what you have done, I have always wondered what they would be like with a manual. Now due to your inspired genius I am looking at getting a VZ cross 8 but want to ditch the 4 speed gearbox and replace it with a later 6 speed auto. Do you think this is possible and what do you think I would need to do? Thanks for your time and awesome job on your ride.
If it is significantly cheaper than $25,000, then put me down for a preorder.So you guys might be interested in the kit when I get around to designing it
Hi would it be possible to get a copy of the photos of your conversion ,it would be much appreciated.
