Live Axle Setups

[TheStitt]

Hey guys.

I'm looking at playing around with the mounting points on the wagons diff.

The reason for this is that after pulling the body from the chassis, some damage was found where the diff has been twisting and driving the right top shock into the chassis, and damaging both!!!

Now currently the wagon runs a 4 link set up

2 lower control arms and a single upper arm and a panhard rod. (the single upper arm is on the drivers side of the diff not centred)

My first point and easiest fix is to just attatch another upper arm. On the other side of the diff.

However after talking to a few mates and doing a little research on the net. I came accross trianglulated set ups, which run two uppers arms that run at angles to the diff and form a triangle. The benifit here is that because of this trianglation the car doesn't require a panhard rod.

Which for me would be great cause i'm having exhaust vs panhard rod issues.

So what do you guys think, what are they like in hard driven situations, has anyone ever worked on a car with this set up. I believe gemini's had it???


Also I have also been to one way to help with the twisting is to mount the lower arms in line and inder the axles. As right now they are mounted in line but in front of the axle. Can some one confirm or deny this???

Thanks guys any imput woiuld be great.

[clubagreenie]

Look under the rear end of a range rover. They have the exact setup you describe, I have one laying around to look at next time you are around.

[The Witzl]

Nissan/Datsun "Series 3" bluebirds use this triangulated setup you speak of from memory. The upper trailing arms dont come to exactly the same point, but they are at around 30-45 degree angles to the lower trailing arms and come to within 200mm of each other......

..... this is all off the top of my head from looking underneath a couple out at piccies about 3 years ago however....

[Darren]

Bare in mind that the arms will all move in an arc as the diff moves up and down. If the arms are triangulated then they'll want to be closer together at the top of the travel, this would probably be absorbed by the rubber bushes (assuming you're not rose jointing) but is still going to load up and want to bind. It will be worse the shorter the arms are too, the shorter the radius the tighter the circumference.

4 long parallel trailing arms with a watts link and roll center adjustment would be best in my opinion
I'm sure some 9" diffs come with the watts link mount on the back of the housing, food for thought.

From dodgy alcohol affected memory Gemini's had the nose of the diff (torque tube) mounted to the car and still used a panhard. Drop the clutch, the nose of the diff try's to turn up lifting the back of the car transfering weight to the front instead of squatting and transfering to the back.

Darren.

[mrshin]

Long live the HQ! They use the type of system you're talking about. While I guess it would make it easier for the exhaust, personally I don't think I'd be getting rid of the panhard, unless you replaced it with a watts link.

[oldcorollas]

Mal McKiggan runs a triangulated thingy on the bottom of his diff.,.. stil with leaf springs, in his classic adelaide KE15..
i think he saw it on alfas? can't remember...

but yeah, it's a simple system and seems to work.... check around if the triangulated bits are usually used on the top or the bottom.. i believe it changes the roll centre of the diff depending on where it is attached..

[takai]

Triangulation is normally on the bottom of the diff from what ive seen. Pretty common among rally cars as well.

[BeRad]

look on some minitruck sites there all into that stuff to use airbags etc they'd know a lot more about it all

[crownv8]

You may be able to solve a lot of the issues with urethane bushes and maybe a second upper arm. A triangle style system would have to be pretty rigid to entirely take the place of a watts link or panard rod. Even the HQ's had rear end issues that were fixed by fitting a panard rod.

The MS112 crowns had a bracket that bolted to the chassis at the top so a "pin" type top mount shock can be used. That may even solve some issues.

Shane

[Gold28]

G´day Stitt,

I think you will run into more problems with the triangulated set up as it will more than double the load in the arms and mounts, plus you have to clear things like exhaust and tail shaft and I know you don´t want to damage one of them again... I know how you drive and you definitly don´t want to compromise the strength of any part in that pore old car.

A good 5 link setup is hard to beat for a live axle and it shouldn´t be too hard to fit in. If you are having problems with the panhard rod, I would have a look at a watts link, something like what is on an XD/XE Farimont (old boxy ones like Nerolies).

[Rodger]

A book I have been reading has a fair bit on chassis setup and tuning.

It is called "Chassis Engineering"

Author: Herb Adams

Published by HPBooks

It is all about chassis design , building & tuning for high performance handling.

Well worth the read as it goes through a lot on rear end setups and the various configurations it is biased to typical "yank tanks" (pontiacs, transams corvettes) but relates to all car makes.

I could start to quote from it but there is a lot of info.

Chapter 9 is titled "Live Axle Rear Suspension Design". Herb describes one version using two lower angled arms mounted to meet at the axle centreline. This eliminates the need for a large high-strength joint at the axle housing if using a single solid A shaped arm instead.

Basically he says you can use standard bushes or rods ends, that are sized the same as the original arm mounting bolts (12mm or 14mm, I think they are?) and standard OEM sized materials for the chassis and diff brackets.

Regards

Rodger

[TRAV-KE55]

The triangulated top arms arnt the go, trust me on this, i have driven a couple of race cars with this setup standard from the factory and they are just a comprimise to a good 5 link. Datsun sunnys, bluebirds, torana's, HQ's all had this setup, and they all suffer from rear suspension bind. Both the sunny and the bluebird steer the rear axle asemble making it good awefull trying to balance a car on the limit, and the torana and HQ suffer pretty bad from single wheel action due to the suspension not working well. All of these simptoms are exagerated when the rear bushes start to suffer a bit ecspecially the rear steer part.
For what its worth keep the panhard and turn it into a straight 4 bar setup.
Trav

[Pube]

Check out this address http://www.mcdonaldbrosracing.com.au/ might help explain a few setups as there are a few pics here. I think you should also take into consideration on what the car is going to be used for ie. for street, track or strip. I would personally still take into consideration a triangulated setup for its simplicity and effectiveness. For street duties especially. Have a look at the mini trucking scene, they are using these setups and are having great success with them and when designed and installed correctly will not bind much at all and these trucks have far greater suspension travel than any race car will ever have.

[TheStitt]

thanks for the repleys guys Crown V8 I am running a MS112 rear end can explain more whbat you are talking about

[crownv8]

The rear shocks in my car and on the MS112 have a top mount similar to the top mount on the front shocks in your car. Just a threaded pin sticking straight up. Gives a better range on movement.

They have a mount that fits to the shocker and then bolts up to the chassis. If you can measure between the bolt centres on the top shocker mount on your chassis I can measure these brackets to see if they will bolt straight up.

Cheers