Team MightyBoy

Just checking the possibilities of swapping the one leaf for multiple versions...

If the three leaf from the hatch is a straight swap with ride benefits, would the four leaf from the sierra be suitable for carrying a little too much weight in the back (Permanently)?

The length of the end to end measurements is the same, so hopefully this will work out better than my current pump up air shocks!

You will find the ride harder/harsher that is certain. At least talk with your local suspension specialist about your idea & also a mods engineer/approved person - if you have an accident after starting the modification, you will be in more trouble than you need - does not matter who's at fault. A mod that has not been approved changes the status of all insurances. It becomes similar to D.U.I. - the other driver is protected from fault

I understand the caution involved with using alternative suspension, does this mean that the three leaf from the hatch is acceptable without engineering approval - or any change is considered risky?

Even if the four leaf swap requires engineering approval, (it's not for a harsher ride - just for carrying permanent weight that seems to be flattening out the single leaf original) is it a direct fit for a sierra rear axle set up into a mighty boy?

(The reason I initially used the pump up shockers was to avoid the engineering issue)

The three/four leaf is actually better than pump up shocks - the shocks unload the springs & put excessive stress onto the shock mounts. I have seen this fatigue the shock mounts & punch the shock through the floor of the vehicle. I am aware ride is not aim of exercise - but it will change anyway.
Like I suggested, talk to a suspension specialist - preferably one who resets springs, not just install packages. The specialist will have the knowledge & expertise to tell you what your best option is & whether engineering is required for the chosen option.

I say this because 1. I am in Qld. not certain of your Loc. rules may differ.
2. I am not qualified mechanically but experienced with home mechanics & have spent 6years plus in the spare parts industry.

You may find the engineer only needs to be involved if a GVM upgrade is involved - depends on your local modification codes.

if they're a straight bolt in i wouldn't imagine you would any type of approval. Also, 99.99% of people wouldn't know what comes from the factoy on a mightyboy anyway.

I work at TJM and set up 4x4 kits all the time, we use shocks on vehicles that are out of the ordinary that are designed for something completely different.. (eg. 5" lifted patrol using landrover shocks or something similar)
Springs would be a completely different thing (as gadj said) you need to consider that the mightyboy only has a 300kg GVM including passengers so having super heavy springs will mean you'll need all that weight there all the time to make the thing stay on the road and not bounce off.

I may be wrong but from playing with suspension at work and at home thats just what i think...

My own thoughts... poly-air bags
poly-air in sydney can almost custom make you a set in they're red series (the lighter duty ones but enough for a mightyboy/hatch/alto) and you'll have some adjustability in them too.

Take care,
Steve

Ok, I might just give it a go then.

I don't suppose anyone knows off hand if the width (left to right) of the sierra axle and the mighty boy rear is similar?

(Strongly suspect mightyboy to be narrower...)

Narrow track Sierra has the same overall width as an MB, but how you would use a RWD axle/diff setup with 5 stud hubs and larger brakes on an MB is another question entirely!

So apart from the spare wheel not being usable for both front and back, I'm wondering if you were mentioning the larger brakes and hubs from a 'not going to fit anyway' point of view?
(The prospect of a north/south motor set up is the only interesting part of the sierra rear axle...)

My point was more that the brake bias would be thrown out, you'd need to find 14/15" wheels in the right offset to fit inside the arches, and you'd have a rear diff setup connected to nothing. Seems like a pretty pointless modification. If your aim is to eventually change to a RWD configuration then I'd be discussing that with an engineer before you even bothered starting the job.

I've only ever seen a handful of RWD MightyBoys, and none of them were street registered... with good reason!

The springs I need now, but the rwd set up can go in the cupboard for a rainy day...
Refering to the RWD conversions that didn't make it to road use, was that due to the alternate motors being unrealistic?

I'm sure the motor choice was a large factor, but from my discussions with an engineer apparently the amount of necessary firewall modification and lack of end to end chassis rails would make a RWD conversion difficult. I wouldn't say impossible, because anything is possible if you have buckets and buckets of money to throw at it.

Spot on Brayden! All 4wd MightyBoys that I have seen are on LJ50/80 or sierra chassis. There is only one exception, it belongs to a forum member not too far from me & is currently not yet assembled. I hope I haven't divulged too much. It won't be an off-roader

Who's that gadj?
like to talk to them... lol

Steve you have nothing to worry about as long as you don't start answering yourself back!!