S550 Rear Differential Mount Bolts - ISSUES & RESOLUTIONS: Pics!

BmacIL said:

Nice pictures! Didn't do the bushing inserts while you're in there?

Click to expand...

No it was not needed. I am going to autocross my car more than drag race so Kelly said the stock bushings for the diff will be fine. The diff bushings only see a bunch of deflection when loading up the driveline and dumping it to take off at a dead stop (Drag Racing). I have other things I did while in there to fix the IRS up. I will post the pictures once I finish everything.

Hello Kelly,
I think I remember awhile back you said you might make a through bolt kit for the stock GT bushings...like it would be part RH018 or something. Don't see that on your website. Are there any plans to sell something like that? I use my GT as daily driver and did not like the noise from aftermarket insert bushings.

Thanks

BC said:

Hello Kelly,
I think I remember awhile back you said you might make a through bolt kit for the stock GT bushings...like it would be part RH018 or something. Don't see that on your website. Are there any plans to sell something like that? I use my GT as daily driver and did not like the noise from aftermarket insert bushings.

Thanks

Click to expand...

I have a stock bushing specific kit.

You have to call to order it.

(2) RM1634 sleeves
(2) HW487 90mm Bolts
(2) HW046 80mm Bolts
(4) HW014 Washers

This kit places more shank into the front bushings than the stock and fills the void in the rear bushings. The front and rear bolts are a grade 10.9 zinc plated design with a shank that is approximately 1.23mm larger in OD than the OE fasteners.

Cost is a touch under $40 shipped within the 48.

BMR Tech said:

-Your through bolt arrangement is a 12.9 grade and can be torqued to a higher value than the 10.9, although slight...that additional amount adds significant clamping force and will likely allow the mating surfaces to stay in place. Remember, the issue isnt necessarily the gap...but the surfaces "slipping"....which enables the bolts to contact the sleeve with force.

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@BMR Tech How much more should a 12.9 bolt be torqued? 129 ft/lbs applies to 10.9 hardware I believe.

Thanks,
Tony

BMR Tech said:

I have a stock bushing specific kit.
You have to call to order it.
(2) RM1634 sleeves
(2) HW487 90mm Bolts
(2) HW046 80mm Bolts
(4) HW014 Washers
This kit places more shank into the front bushings than the stock and fills the void in the rear bushings. The front and rear bolts are a grade 10.9 zinc plated design with a shank that is approximately 1.23mm larger in OD than the OE fasteners.
Cost is a touch under $40 shipped within the 48.

Click to expand...

Thanks Kelly I will call in next week.

lxh89 said:

@BMR Tech How much more should a 12.9 bolt be torqued? 129 ft/lbs applies to 10.9 hardware I believe.

Thanks,
Tony

Click to expand...

We typically torque 12.9 about 15% higher than 10.9.

But, and a big BUT...that doesn't mean we recommend that if you use the stock style configuration where you torque the steel fastener into the aluminum bushing and diff cover. In this case, we recommend sticking to the factory 129ftlbs regardless of bolt Grade.

When through bolting though, 148-150ftlbs is what I suggest.

BMR Tech said:

We typically torque 12.9 about 15% higher than 10.9.

But, and a big BUT...that doesn't mean we recommend that if you use the stock style configuration where you torque the steel fastener into the aluminum bushing and diff cover. In this case, we recommend sticking to the factory 129ftlbs regardless of bolt Grade.

When through bolting though, 148-150ftlbs is what I suggest.

Click to expand...

Great - thanks for clarifying!

Tony

A few people called to order an upgrade kit for the stock bushings, so figured I would show them as the "kit" listed in post #138 above.

These pieces add strength in a few ways.

1: They are the same 10.9 Grade as the OE fasteners, but they feature shanks that are over 1mm larger in diameter.

2: The front bolt shanks actually protrude into the inner bushing sleeve, where the stock bolts stop well short. This does a few things - it places the shear path on the shank, and it also helps to retain the pinion mounting and location IF the bolt snaps on the threads which are tucked deep within the bushing. It does not allow the threaded portion of the fastener to continually bend and deflect. I have had about 25 people install these front bolts with zero issues to date.

3: The rear bolt is essentially a duplicate of the factory piece, except the mass of the bolt and diameter of the shank is larger. However, it is impossible to place the shear path on the shank without drilling through the differential cover. This kit includes the bolts, but ALSO the CNC machined insert sleeves to center and lock the mating of the differential and the subframe. By doing this, it helps prevent the bolt from deflecting excessively as well as helps keep the bolt from seeing damaging shock loads when it is "floating" within the stock bushing.

BMR Tech said:

A few people called to order an upgrade kit for the stock bushings, so figured I would show them as the "kit" listed in post #138 above.

Click to expand...

Thanks for the pictures. Looking forward to getting these in.

BMR Tech said:

I have a stock bushing specific kit.
You have to call to order it.
(2) RM1634 sleeves
(2) HW487 90mm Bolts
(2) HW046 80mm Bolts
(4) HW014 Washers
This kit places more shank into the front bushings than the stock and fills the void in the rear bushings. The front and rear bolts are a grade 10.9 zinc plated design with a shank that is approximately 1.23mm larger in OD than the OE fasteners.
Cost is a touch under $40 shipped within the 48.

Click to expand...

Hello Kelly,
Getting ready to install these stock bushing replacement bolts. Just so I know before I get started, do I have to drop the subframe in either the front or rear to get these bolts in?
Looking at some of the pictures in this thread it seems maybe I don't have to drop the front subframe to replace the front bolts but might have to drop the rear subframe to get the rear bolts out and replaced.
Let me know if that is correct. Thanks!

Wow..I thought the rear IRS bolts had the same problem as well but no reports of them breaking.

This is Fords first iteration of an IRS on the Mustang so we'll just have to let them make it. -shrugg

However I think some of this should be against fastening design rule. A bolt should never be threaded at the bearing surface/length of the bushing surface and this length should be a tight fit??

Also a recommendation on the first page, your picture titled "FACTORY FRONT SIDE DIFF MOUNTING" is still in the mix with the RR bushing explanation. This had me confused for a sec.

JKL1031 said:

This is Fords first iteration of an IRS on the Mustang so we'll just have to let them make it. -shrugg

Click to expand...

Not exactly the first. Though it is the first iteration for IRS being applied to the entire Mustang lineup.


Norm

Trying to decide if i should upgrade to the lockout or leave them stock. Im sure I dont drive anywhere near as hard as boardkat.

Anyone who has put through bolts on the front, how did you lower the cradle enough to drill out the cradle bushings? I have l lowered my cradle as much as I can with it hanging from all four bolts and I’m nowhere near close to being able to get a drill bit in there. Any help is greatly appreciated.