Gearbox conversion on a HJ47

Jim, I did a simular conversion on my 83, 47 using a earlier 75 series gearbox and transfer case.

The whole thing moves back about 70mm so you have to lengthen the front shaft and shorten the back one, and cut the floor pan as both levers move back the same amount.

The handbrake goes back on the rear of the transfer case and the lever stays in the same position.

The tube welded between the rails has to be modified and new mounting brackets made, but it all fits in with the 80 ltr aux fuel tank.

As for power take off you can use the 75 series pto and shaft and this will mate up to the thomas.

All in all a great conversion, but when you do the power steering bit it transforms the 47 into a real good off roader.

That's ok Jim, what ever 5 speed you use they are longer in the gearbox section, the 5th gear is outside so to speek, that makes it longer.

I reckon you will have buckleys trying to find a 40 series 5 speed, so why not go for the later 75 series.

The welded tube is situated at the rear of the transfer case, and with the handbrake attached you cannot slide the gearbox into position as it hits against this tube. It must stay there as it gives the strength to stop the rails from moving appart/together.

Once again its worth the effort.

hey jim,
i have the same vehicle as yourself and was going to do the same thing or put an overdrive on my 4 speed. got heaps of info but ended up not doing it.lack of money.
however i got some useful info i thought you might like to know. after talking to a few mechanics and conversion specialists i decided the best option was to get an overdrive. apart from the huge price difference between an overdrive and a 5 speed box i found the 4 speed box was considered a stronger box than the 5 speed. also the overdrive was far easier to install.basically bolt in on to your 4 speed and put the gear lever next to your 4 speed lever.(i think there is a spot in the floor for the overdrive lever to go into).
the thing i was told not to do was leave the overdrive on all the times. it destroys the bearings.only engage it when the appropriate speed was reached.
i would say in your case as well with a pto by putting the overdrive in you wouldnt need to worry about it affecting the pto.
well anyway thats my 2 cents worth.hope it helps. go the troopies.

have a look here this guy is in to al sorts of conversions and easy to talk to on the phonehttp://www.rodshop.com.au/index.htm

I have been through the whole issue before with my HJ47 2H diesel 84 model. The esiest, cheapest and simplest method is to buy your own low maintenance overdrive commonly known as 33 inch tyres. You can get parts for them anywhere, maintenance is a simple blow up with air and you will not have to change clutch, box, tailshafts and diff centres. The 5 speed option fitted will be $3500.00 for it to be a proper job. If your springs are standard height they will fit. I used BFG 33 x 15 x 9.5 and they can legally go on a 7 inch rim. Any wider they will need an 8 inch rim. All terrains will give a quiet quality ride. I bought them from Competition tyres in Warrigal rd Murrumbeena Vic. They were $215.00 each. The best price in Aus. With this change I got a new top speed of 130 and the engine revs on 100 dropped 600 rpm. Reduced engine noise and fuel consumption. Speedo was a bit out however a gear can be purchased for the speedo cable that will correct this. Positive thing is that 1st gear becomes a bit more usable and gets you going much better.

Do it its is the best option. Andy

Hey Jim, Take it from Me I did the conversion and it is easier than a lot of people are telling you . I performed this conversion on my HJ47 ute and it is easy(depending on your mechanical aptitude of course). I installed a '86 HJ75 Box and transfer but the 60 series is the same I think
I did not have any problems but you need to do the following.
1. The Gearbox mount needs to be re-positioned slightly lower, I achieved this by slotting the holes in the mounts so the gearbox did not hit the body. It only needs to come down by 5mm so you dont lose any ground clearance.
2. the transmission cover needs to be re-cut and MIG welded to accomodate the different lever positions and the transfer lever needs ot be bent slightly so it does not hit you leg and you dont know it out of gear accidentally.
3. The transmission handbrake goes, unless you find a transfer case from a 5 speed 47 and swap it over. Put on 60 series rear backing plates with all the insides and a 60 series handbrake cable will fit, although a little tight when activated, just protect the cable on the sharp edge of the fuel tank so it doesnt rub
4. You need to have your tail shafts lenthened and shortened to suit. I chased the wreckers but could not find any the right length.

I installed the gearbox with the engine attached so had no problems with the cross member. I have since rebuilt the transfer case and the only issue with the tubular cross member was that I had to drop the rear of the engine down to get the transfer out which was no probelms.

Well worth doing, reduced the fuel consumption considerably, adding a turbo is also a worthy conversion.