“Britney, why do you pollute my space?”

I look around and all is revealed: A backward capped buffoon in a neon-lit Lancer, long forgotten in a fibreglass frenzy, pulls up beside me...

He seems entranced by the silicone-titted teen diva’s inane moanings. I figure one hard launch on the green and I’ll have wasted this bozo by the end of first. 

Green. Then the unthinkable happens. A cocophony of splintered gears, grinding metal and a distinct lack of forward propulsion. The tinny, farty exhausted Lancer fades into the distance. The lyrics “Oops, I did it again” seem strangely prophetic….. 

I awake from the nightmare, startled, in a cold sweat. With my heart pounding, I reorient myself. I establish this didn’t, in fact, ever happen. But it could. I resolve, there and then, to engage in a pre-emptive strike. To do the Hilux. 

Here is my story. 

Hilux Diff

My diff conversion had to fit a few criteria:

·        Strong and reliable

·        cost effective

·        easily interchangeable gear ratios

·        easily procurable limited slip differential (LSD)

·        disc brake setup

·        5 stud 114.3 x 5 PCD 

This immediately ruled out a large number of potentials. In the running were the Ford 9”, Borg Warner and the Hilux diffs. 

The Borg Warner has major short comings. They are probably the weakest of the three, are prone to developing gear whine and it was impossible for me to easily swap out the diff centre in my backyard. I understand the LSD mechanism is terrible and will start to slip after only limited driving. That said, they are cheap and there is a plethora of disc brake setups readily available. This may be an option for some – but not for me. 

The Ford 9” seemed like a reasonable option. Their strength is world renowned, it possessed the right PCD and the LSDs are readily available and easily interchangeable. Again, there is a multitude of disc brake setups. The main issue here is cost. LSDs in the gear ratios I wanted were not cheap at all. Estimated cost blew out to over $2000. And, damn, are they heavy!!! 

The Hilux diff is the last option. It has an 8” crown gear (G series for the Toyota aficionados), chunky axles, the correct stud pattern, cheap as chips and LSDs that are relatively cheap and readily available (in the ratios I need). The diff centres are easily swapped out. They are a bit lighter than a Ford 9”. The only problem is that there is no disc brake setup that is commercially available for the Hilux. 

Jigsaw puzzle 

G series diffs are found in Hiluxes or Hiaces – there may be others that I’m not aware of but these will be the cheapest options. I needed a track width of approximately 1410mm, and the early Hilux (model RN41) suited perfectly. The Hiace diffs appear to be around 1570mm. 

The next required item was a Hilux LSD. They are a 4 pinion LSD, and use a clutch pack mechanism to limit slip. The clutch packs are metal, rather than the trashy fibre ones found in other clutch pack LSDs. A wide range of ratios is available (3.7 right through to 4.3:1). 

Whilst at the parts importer, I made a fortuitous discovery. There, in the dust, lay some Celica ST205 rear 2 spot calipers. Further scouting around the yard identified the ideal rotors for the disc brake conversion - Supra JZA80 non-turbo rears (307mm x 18mm – DBA746). A Mediterranean haggling match ensued and the calipers and rotors were thrown into the fray for additional bargaining power. After 10 minutes of discussing potential respective bankruptcy, world politics and Megan Gale’s ample breastage, a deal was struck. Herein, lay the beginnings of the disc brake setup. 

So will this crap fit together? 

The Pepsi Challenge 

Firstly, I took the Hilux diff off to have the Corona Mk2 suspension points welded on. Any good diff place will be able to do this, or at least, point you in the right direction. Of course, you will need a diff housing for them to cannibalize for the suspension points. Prices for this seem to vary from the 300 – 500 mark.

The rotors fit straight on to the Hilux axle, but required the central hole to be machined out to 67mm (from the standard 62mm) for an absolutely perfect fit. The calipers were a little bulky – either they had to be machined a little or I had to accept that the pads would sit a little proud of the rotor. I decided on the latter. So, it’s off to the machinist to make a caliper bracket. This is an 8 mm thick mild steel plate with holes for mounting to the diff and also some spacers to set the correct caliper spacing. Easy, so far. 

The dilemma arose in my quest for a handbrake setup.

There are 3 options:

  i.)        integral caliper and handbrake

 ii.)        hydraulic handbrake, and

iii.)        internal drum handbrake.

Scrap option 1 – I already had the calipers so I wasn’t going to spend more money. It certainly simplifies things, but generally they are of poor design and are big heavy cast iron units. They are most commonly seen in Ford Falcon rear disc setups.

Option 2 made me nervous – although very commonly used by rally drivers, this is more as a ‘driving aid’ than an emergency stopping mechanism. Should I have a hydraulic failure, I would have no means of stopping. Er, no. 

So option 3. As it happens the JZA80 utilises an internal drum handbrake. The drum diameter is 190mm. 

So what else runs a 190mm internal drum handbrake? After an exhaustive search of the DBA database, I came up with these 5 options:

  i.)        JZA80 Supra/xZ30 Soarer

 ii.)        MA70 Supra/GZ20 Soarer

iii.)        MY02 Subaru WRX Sti

iv.)        VT Commodore

 v.)        Tickford Falcon. 

MA70 and JZZ30 rear hub carriers/backing plates seemed to be in plentiful supply at the import wrecking yards. When I checked them out, they had a central hole that was almost the same size as the Hilux axle bearing carrier outer diameter. With only a small amount of machining I reckoned these would be the go. I obtained some MA70 backing plates. Unfortunately, I had to buy the whole hub carrier and press out the hub to get the backing plates - I was able to sell the rotors and calipers to offset some of the cost. The central hole was machined to fit over the Hilux axle bearing carrier (from 102mm to 105mm). Four holes were drilled in the backing plate to suit the Hilux diff bearing flange pattern but this required the removal of a small amount of material which supports the drum pivot pin. The backing plate was installed with new bearings pressed on to the axles. Four splined, high tensile steel bolts then hold the backing plate, axle bearing carrier, and caliper bracket to the diff bearing flange.

A trial fitting outside the car showed it all went together beautifully. It was dismantled and reassembled on the car. Perfect! I was able to use the factory handbrake cable and the general fit looked factory. Very happy!

To save money, I'd suggest that you just use the MA70/GZ20 rotors and calipers as you have to buy them when you buy the backing plates. They are 291 mm in diameter and will fit under a 15" wheel, and can fit under certain 14" wheels (Ford 14 x 6 steel wheels).

Pricing 

Here is an approximate pricing for my Hilux diff conversion. Obviously, prices will vary from wrecker to wrecker, machinist to machinist. My suggestion is to shop around and use who you are happiest with. I did all my own removal and assembly work - expect costs to escalate exponentially if you decide to get a shop to do all the work for you. All prices quoted are in AUD.

Whilst many hours of research (scouring databases, pottering around shifty wrecking yards with Verniers) went into this conversion, it is really only a suggested method of converting a Hilux diff to disc brakes. Of course, there may be other ways and there may be cheaper ways. It does demonstrate that it is possible. I hope it helps you with your conversion.

Fuck off and die, Britney.

Fig 1. A side view, showing the relationship of the caliper, rotor, bracket and diff housing flange to each other. Very neat fit.

Fig 2. A shot showing the face  of the rotor. In the background are some ST205 front calipers, which have made their way on to the front of a certain MA61.

Fig 3. Rotor fits straight on to the Hilux axle after a small amount of machining of the central spigot hole. In fact there is even a hole such that the little drum locator screw can still be used!

Fig 4. Corona Mk2 suspension point brackets welded onto the Hilux diff. Any good diff shop should be able to do this or point you in the right direction.

Fig 5. Here is a shot showing how the bracket mounts the caliper and also to diff housing.

Fig 2. Megan Gale. This delectable West Australian has set Italian hearts racing (mine included) with her classic good looks and ample cleavage. Grrrr.  Specs: Date of Birth:                 7 August 1976 Place of Birth: Perth, Australia Horoscope: Leo Hair Color: Black  Eye Color: Green Height: 180 cm Weight: 60 kg Bust-Waist-Hips: 90-60-90 (cm) Dress Size: 42  Shoe Size: 41  Marital status: Unmarried  Education: High School

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