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10/14/2013 10:28 pm  #1

Jag IRS install-- Is this correct?

This is a humble farm truck resto mod. A previous craftsman installed this rear end several years ago. My current builder is questioning the stability and durability of the installation. Do I need to have further fabrication done? This install looks very similar to others I see on this site, kinda encouraging! Any input greatly appreciated!


10/15/2013 7:50 am  #2

Re: Jag IRS install-- Is this correct?

I think I can see on thing wrong but it could be the angle of the picture.  Can you post a picture showing the front of the unit?
There should be a front brace which goes from the lower control arm mounts to the frame.  This prevents a rotational twist. 
Also, if much power is going to the unit (better than say 1 hp per 15 pounds of vehicle weight), the top mount is kind of crummy.  It isn't so much you need an isolation mount (kind of nice though) as much as the four bolts running through the top of the cross member don't do much good.  They may hold it in place but are subject to breaking in this setup. 

Take a look at the Cross Member kits here for an example:

I'm not endorsing them, they just happen to have a good visual.

Your builder isn't far off track.  Be sure though to ask him specifics.  He may see something I've missed.  However, if he starts bashing the decision to use any IRS system, he is either incompetent with IRS needs or he wants more money from you.

Good luck and let us know how it goes!


10/15/2013 11:24 am  #3

Re: Jag IRS install-- Is this correct?

Post more photos. Especially on the front side. I'm not seeing any torque stays or trailing arms.

97' C5 Corvette, 46' International Harvester K3 Street Rod

46' International "Harvester of Sorrow" Build Thread

10/24/2013 12:20 pm  #4

Re: Jag IRS install-- Is this correct?

So here is my plan after talking to a local shop that does a lot of Jag IRS work:     Dave You must have pinion support bars extend from lower inner control arm pivots to frame. parts illustration is on our web site under jag install kits.

I will post more pics soon.

     Thread Starter

10/25/2013 7:49 am  #5

Re: Jag IRS install-- Is this correct?

Once you get the pinion supports, I would suggest one of the following mounting points to the frame:
Box a 1 foot or so section of the frame with the mount going to the pinion in the middle using 1/8th in plate
Place the mount at the top part of the inner C-Channel

Both will help distribute the load through the frame.  If your experienced builder has other ideas, they will likely be better.


10/27/2013 7:42 pm  #6

Re: Jag IRS install-- Is this correct?

Well it looks like I have found the answer to all my questions less than 5 miles from my front door!
Curt Hamilton at Hamilton Automotive has been doing these things for a long time.

Here is the start of what he has hooked me up with:

He's a great guy and is in there every morning inc. Sat and Sun at 5am!(?)

I'm in good hands and can't wait to show some finished pics!

Here is the before pic from the front:


     Thread Starter

10/28/2013 8:07 am  #7

Re: Jag IRS install-- Is this correct?

It's awesome you found a resource so close!  Too bad he doesn't have a web page.

Can't wait for the photos with the updated components.


10/28/2013 12:57 pm  #8

Re: Jag IRS install-- Is this correct?

That is good news - finding a local shop is always a surprise.  Just the other day I found this guy's shop - 3 miles from me - so IF/When I need to spend $ome buck$ on Carbon fiber:  some pretty cool stuff

Looks like you're set up for a great mod - and support as you go.  Good Luck -
Cheers - Jim

UNDERCONSTRUCTION! Highly Modified C3 Corvette
         Dual Wishbone IRS w Subframe + Custom Uprights

12/06/2013 12:03 am  #9

Re: Jag IRS install-- Is this correct?

Still hashing this out with my two experts. Mr. Hamilton would like to know the stock frame height before he can decide what to do next. I am going to tell him to shoot for 20.75 to the top of the frame front and back. This is based on the diagram I found of a stock 56 w/ 16" wheels that is 21.25". He seems to be leaning towards a solution to widen the frame 2-3 inches around the rear axel to provide clearance for the shocks. Mr. Hamilton wants to fab the sub assembly and have my builder cut the frame and install. My builder is stressing out and says this is not within his skill set, which I do understand. One way or another I do believe something very cool is about to happen.

     Thread Starter

12/06/2013 7:40 am  #10

Re: Jag IRS install-- Is this correct?

Just curious  but is there any reason the top shock mounts couldn't be mounted outside the frame? 4 coil overs on that light of a truck I'm not seeing a lot of travel happening. 


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