brake booster upgrade

I thought the HJ 61 had a twin diaphram booster. Maybe source one of those. If braking is a problem is the vacuum pump actually creating sufficient vacuum depression. If not, changing booster may not solve your problem. If vac pump is clogged by crap from dirty oil it may not work well. Also, the oil viscosity delivered to the vanes may be a bit thin, which also affects degree and quantity of vac being made. Has the alt been changed and has a larger pulley than before? Do you have larger wheels/tyres which degrade brake performance?

Give Bramac Brakes in Rockhampton a call (after holidays,closed until ~Jan 3). They are very knowledgeable and helpful. Just an old customer.

Sooo
long story short of it is..
I have a hj47
Standard 84 with nil factory upgrades like power steering or 5speed but i have the factory AC.
I have always had terrible brakes.
I went to slotted rotors.. and that helped the front a little.
Rears are drums..
We pretty much run exactly same drivetrain except you have wider diffs.
I run a heavy setup around 3t gross with the canopy ... fridge
I adjusted the lpsv myself.
But brakes were still average.
Soo after a few years i found a really good brake shop who does custom stuff.
He made up a pressure guage and tested the brake pressure.
Vacuum was lazy..
Soo we replaced the alternator.
As the V Pump is on this in the diesels.
Ok.. soo we got vacuum.
The rear pressures needed to come up .
Soo lpsv was adjusted again.
A further 25mm via a new bracket.
Now pressures come good.
But when im on a steep hill.
I really have to put 2 feet on the brake pedal to stop me from rolling back.
Soo its really struggling to hold hills with light brake pressure.
We used a toyota surf booster and it bolted straight up.
But the pushrod needed cutting down or something.
We then were able to source a new hz80 master cylinder for even more pressure.
It works brilliantly
I can be 3tonne gross AND tow a 1tonne trailer and hold it on a hill with very little brake pressure.
One foot and possibly 2 -3 kg of force will hold the ute on any hill.
Where as before at 3t gross
I would need both feet on the brake pedal and id have that much pressure on the pedal my back would be pushed into the seat !!!.
It wasnt a very expensive exercise in the end.
Funny though..
I was getting this brake work done and while he was testing the old setup..
The pushrod snapped on the brake booster and he had to use the good handbrake i had in the ute.
Of which he never even got on the road.
This happened between the rear yard of the shop on the driveway.
Soo i really did perfectly time this upgrade.

I would suggest raise your lpsv 30mm at a minimum
And maybe another 15 - 20mm on top of that if you feel no difference.
A crued method is to find a dirt road and try locking the brakes up at a low speed like 20 - 40km/h.
I did find a small improvement as i felt the back end did help the front a bit..
But i didnt go any further adjustment but i should have done and 25mm.

Im running 33x 12.5 x 15 bfg muds
Drum rear
Factory disc... but now slotted
Noo braided brake lines.

The booster and master cylinder upgrade is the best thing ive done
I now feel confident in pulling the ute up in any gross weight i am.
Cruisers from 40 - to the current hdj to the newer vdj series have woeful brakes as they were made from factory.

I had a 1985 HJ75 which has the same 2H engine set up.
From the day I bought it the brakes were woeful and over time checked this, that and everything looking for the problem. I pulled the vac. pump to pieces a couple of times thinking the vanes were sticking in the rotor but no.
Then one day was discussing this with a mate and he asked for a look under the bonnet. Funny thing, he says, your vac. pump looks shorter in length than mine?
And so it was, got one from the wreckers same length as his but something was in the way behind the alternator which prevented it going on.
I was able to change something to make it fit, its a long while ago now, but the brakes were excellent from then on.
I have no idea why there would be 2 different lengths of vac. pump fitted.
mike

If the brakes on the HJ61 has the twin diaphragm as RMD mentioned it may be an easier change over. I had 1986 HJ61 sahara they are a couple of hundred kg heavier from the factory than the base 60ser and I found the brakes fine empty, loaded or towing with standard brake pads as well.

It would also pay to replace all the old rubber brake lines if you haven't already that can make a noticable difference and fit a better brake pad that offers more grip like Bendix. Make sure the rest of the brakes are clean, adjusters work correctly and you have no fluid leaks at all. You can do the discs, drums but it may not be needed. It's easier to upgrade the basic items first before the booster as well it may be all you need.

If you have a lift kit of any height above factory make sure the rear brake bias has been set up to suit so it's back to factory spec to start with every bit helps as it will effect the braking.