Independent Rear Suspension, OEM, aftermarket, stock configuration or heavily modified, all makes and models, everyone is welcome here!!!

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12/14/2013 5:12 pm  #31

Re: HugoW's Jag IRS conversion project and plenty questions!

There is or were kits with the nylon bushes being made. Not sure if they are still available. The bolt pattern on my Jag RA is the same as the Chevy 5 x 4-3/4 so that opens up wheels choices a bunch.  I narrowed mine so 15 x 10s would flush with the wheel well instead of sticking out. I still have room for 12" wide rims if I go with a 6" backspace. 


1/30/2014 6:31 am  #32

Re: HugoW's Jag IRS conversion project and plenty questions!

Well, after a long rest I took another look at this project, and here's what I came up with:

I think I will make brackets so I can fit the tops of the coil-over units in different locations. So, normally, with no load at all, they will be set inward. Should I ever decide to use the truck to actually haul anything, it takes a few nuts and bolts and the suspension is stiffened up. Not likely this will happen often, hence I think it is an easy choice.

What to you guys think?


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6/10/2014 4:12 am  #33

Re: HugoW's Jag IRS conversion project and plenty questions!

Hi guys,

slowly working going both forward and backwards on this project. I have the truck frame all measured up and drawn (progress) but I seem to have lost my files in a server swap so I lost the CAD I made of the IRS unit, the one I made the pictures above with. Would someone be so kind as to share some dimensions I miss:
- What is the horizontal dimension between the upper strut unit mounting points? I no longer have the cage.
- What length are the struts compressed, when the drive shafts are horizontal?
The rest I got pretty much figured out from measuring parts again.



Last edited by HugoW (6/10/2014 4:13 am)

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6/11/2014 1:11 am  #34

Re: HugoW's Jag IRS conversion project and plenty questions!

Progress! Well, design-wise. I’ve taken all the tied up pieces off the truck, and started to take it apart further. The first major project will be the rear drive set-up. The rear now looks like this:

Back to front: the rear bumper bar is missing, then there is the first cross member, then we see the axle, then the second cross member. The first and second cross members are mounted at the location at which the current leaf spring suspension is mounted to the frame. Yesterday I measured a lot and made a sort-of template of the frame to copy to CAD. I first cut a piece of cardboard to fit around the suspension mounts:

This cardboard I mounted to the frame:

And with a black marker I traced the frame:

I did both the left and right hand sides, because it seems the truck is not perfectly symmetrical. You can see the left hand side tilts inward, I measured 8 degrees:

The right hand side only tilts in 3 degrees:

This means the new sub frame will also need to be a-symmetrical to fit right, and to have the IRS unit mounted central to the main frame.
At home, I transferred all dimensions and the traces to CAD:

So, here’s the first sketch of what I am going to build as a rear axle sub frame:

I will make a simple new rear bumper bar. Both original cross members will be replaced, and mounted to the frame with flanges using the original holes to which the leaf spring suspension was mounted. There will be a new third cross member, to which the IRS diff will be mounted. The cross bars I hope will add a lot of strength / rigidity to the frame. Because currently the frame is very flexible. All cross members and bars will be sheet metal, U shaped.
Please feel free to comment.

Last edited by HugoW (6/11/2014 1:12 am)

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