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Ford 8.8 IRS Conversion


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You're not actually planning on running it just like that with the diff bolted to the uprights, are you? You need to make a MUCH stiffer assembly to bolt the diff to. Have a look at blueovalz's rear plate that he made, or some of the diff mounts from tssfab.us, the various V8 miata mounts, etc. If you put power to that you're going to fold it like a wet napkin.

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ITS guys crack the uprights at the top, and they're just using them to locate the suspension and they're limited to near stock size wheels. The front mount should control lifting of the nose, the rear has to control the twisting. The twisting is a big deal, which is why the stock mustache bar is thick spring steel and wide.

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I'm also concerned about the strength of the small bolts that connect the uprights to the unibody (and the unibody steel tearing). However, what is the worst that can happen? It breaks and Josey goes to a back-halfed straight axle? Gonna have to cut all that sheetmetal out then anyway. As long as SUNNYZ is doing all the work, I'm all-in and axious to see his first trip down the 1/4-mile!

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Yours looks more expensive! Haha. I'm interested to see how you do the mounts. I was drawing up some braces last night, but in the 25 degree shop, I was having trouble getting motivated.

You would think more expensive but its just a brand new housing with races. So it was a bargain. This way I can choose which lsd to put in. Also it will be alot lighter during fab being empty! I have a couple ideas on how I will mount it but it will be a bolt in setup to stock points on the body. Axles I will wait until you get that figured out. :icon45: Almost time to dust off the tig and get working again.

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It's too late now but i think the weak link was the mustache bar and uprights not the axles, the flexing from the oem components would of caused twist in the algnment of your drivetain causing a break probably consistant with the breaks your having. imagine putting a stick between your legs and pulling the end of it untill it breaks.  Anyway good project and nice build i plan on doing the cobra irs swap in mine as well.  also another note to consider: the angles in which your axleshaft normally reside should match that of which the vehical you pulled them off of ie the for and aft geometry. another anology the way the rear end and the transmission have to be the same angle.

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Got a little done today.


Here is the diff mounted.  PLEASE refrain from the "you need to reinforce it more" comments. Its in the plans!




Perfect clearance, as planned




I also cobbled together a diff mount from cardboard. Probably going to cut out the pieces from steel, maybe tack them together, and then get this rolling. Again, being at a huge disadvantage not having a welder here.




Another shot of the "diff mount"




surprisingly, just eyeballing it  - its fairly square.


Just hanging there, it is sitting with +2 degrees of pinion angle. The trans is sitting at -1 degree, for a total of -3 degrees. I will probably shoot for somewhere in the -2 to 0 degree range, as there is no needed negative as with a live axle.

Edited by SUNNY Z
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