IRS center section bolts

[Alec]

I can't put my hands on the bolts for the IRS center section. On my POL list is something vague labeled "IRS fasteners" (17157) in box 2, under the heading "IRS package parts". Is that the center section mounting bolts? Does anyone know the exact bolt style/sizes so that we can get them at ace?

[edwardb]

If you're talking about the four large bolts that hold the IRS center section to the chassis, according to my records, they're (2) M14-2.0 x 100 flange head bolts, and (2) M16-2.0 x 130 flange head bolts and (2) M16 x 2.0 deformed thread flanged locknuts. They're all called out specifically on my inventory list. Looking at my build pictures, I see those are metric class 10.9 high-strength parts. Doubt very much those are Ace hardware parts and wouldn't recommend anything that doesn't exactly match.

I don't see any record of 17157. But my list is a few years old. They often group parts together with a number. Maybe something that's changed since mine.

[k-roy]

Unfortunately, the parts you are looking for are with the IRS fasteners, and are also on my POL. I emailed Factory Five with missing parts and asked what the ETA was, but never heard back. You are supposed to chase the front mount holes with a 5/8 bit. My father and I are building this together, so he went to the hardware store and bought 5/8" bolts for the front. We ground down the tips of the bolts to help align the holes. I believe the back bolts are 1/2"-13. Do not quote me on that, as my father used my thread checker to get the proper size and he bought the bolts. I assumed (as stated above) that the bolts are hardened, so I have used temporary bolts to hold my diff in place, but are only half threaded. I figured I would take one bolt out at a time and replace it with the proper bolt when the POL was shipped.

174069
174070
174071
174072
I believe this was the nut for the bolt we used.

Hope that helps

[edwardb]

The threaded holes into the back cover of the Mustang IRS are definitely metric. Don't mess up the threads with SAE bolts. It's not unusual for metric and SAE threads to sort of fit into various thread checkers. You could get away with matching SAE bolts and nuts for the front mounts. But need to be the proper type and hardness. The bolts I listed above should be on your inventory list (that's where I got the details I posted) and if you don't have them should be on your POL. Organization is super important with these builds. Especially if you're dealing with backordered parts. Be careful.

[kbmyers]

Thanks Paul, this information really helped! Like Alec, my original packing list showed "17160 IRS PKG PARTS" quantity 1, back ordered. When they did show up, they came in with many other parts in a box and no packing list. Two of the bags were 15963 (M16-2.0 x 130mm bolts) and 15962 (M14-2.0 x 100mm bolts)

Nowhere have I found in the manual what bolts were needed. Just "The larger/longer bolts and nuts are used for the front mount".

Thanks for the info to help me put the puzzle together!

[BRRT]

I pulled this from another post here on the forum. Hope it helps.
https://thefactoryfiveforum.com/attachment.php?attachmentid=192133&d=1699813501

I was missing the long M16 bolts for the front of the differential. I subbed in 5/8-16 Grade 8 bolts and nylon lock nuts, all yellow chromate finished.