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

[BMR Tech]

Found some bent vertical link bolts....

Upgrading them to a through-bolt. Pics coming. :O

Sponsored

 

[BMR Tech]

3 people with diff bolt issues in the past 24 hours. Sharing this thread with them, so figured it needed a good bump.

 

[EcoBOSS]

Is there a bolt kit for use with NO inserts?
DD, want to keep the NVH to a minimum.
EcoBoost PP, 6R80

 

[BMR Tech]

What I have people do on stock bushings, is I have them run a replacement front bolt with a large washer. This bolt will place the SHANK of the bolt INSIDE the center aluminum bushing sleeve on the stock bushings. The factory front bushings have a machined relief - which makes it easy to use a bolt with a longer shank.

I have a VERY hard time believing that some guy who likes to make cars go fast, can figure this stuff out and improve upon Ford's designs. So I am going to guess that placing the shear loads on the threads, and also having the threads exposed outside of this relief is done intentionally. That being said, not my style! I have a bunch of cars around the country testing my stuff and I have not single issue with durability - and several of those people broke/severely bent the stock bolts.

So anyways, here are some pics to explain what I do to make the system more durable in extreme applications.

The photo that really shares detail is the comparo, where the scribed mark (where the pen tip is) shows where the shear path is (where the bushing meets the diff)....and as you look to the right, shows where and how the OE bolt is positioned.

For the rear bushings, just a sleeve like I have shown above with a nice bolt works. The only way to make it better would be to drill the diff ears out.

 

[BMR Tech]

To add, here is the OE bolt that sheared and the one I replace them with.

 

[cop on my back]

I'm getting some strange noises from my rear end. Don't think it is the slop in the diff and splines, might be a bolt. Once my garage floor is poured I will get under it and look.

 

[SteveW]

What seems to be the way to get a broken diff cover bolt out? Get a new cover, lol?

I found a broken bolt on my car.

 

[BMR Tech]

What seems to be the way to get a broken diff cover bolt out? Get a new cover, lol?

I found a broken bolt on my car.

Depends. Enough sticking out to grip it? Was a ton on loc tite used?

Lower the diff to access the hole. Slot the tip and use a screwdriver or bit...and unthread it.

If that's not working...drill it out and through bolt it.

Or get a new diff cover.

Can you share more info? Stock bolts? Aftermarket?

 

[SteveW]

Depends. Enough sticking out to grip it? Was a ton on loc tite used?

Lower the diff to access the hole. Slot the tip and use a screwdriver or bit...and unthread it.

If that's not working...drill it out and through bolt it.

Or get a new diff cover.

Can you share more info? Stock bolts? Aftermarket?

Hello, I don't know much yet. I got under the car this afternoon to work on the rear sway bar and noticed one of the rear inserts missing and by the depth of the hole it's sheared off at the cover. Haven't done anything else with it yet.

I am using red poly inserts by another vendor on here with the original hardware. Probably should have taken the preventative steps of replacing that stuff a long time ago. Dang. I didn't use a lot of locktite putting them in so maybe I'll get lucky with extracting it.

Thanks for the reply! I'm sure we'll be in touch once I get deeper into this.

 

[BMR Tech]

Ah gotcha. Sorry to hear.

What happened to you is pretty common with those items, so don't feel too bad.

Let me know of you need any assistance.

 

[wildcatgoal]

Drill out the threads in the bushing and through-bolt it with 9/16" grade 8's. Issue resolved, more strength than the stock size bolt, and the bolts are easily acquired. Will need to drop the IRS enough to get a drill up there and a long bolt through, but not hard. Through-bolting will increase NVH a little bit - keep that in mind. Steeda's drag cars use the upgraded 12.9 grade bolts (if using inserts). Zero failures and frankly you're more likely to break the ear off of the pumpkin or blow out the bushing than break or bend a 12.9 bolt. This is a weak point in Ford's design and I can't recommend through-bolting enough, although I'm sure someone will break a through-bolt eventually and a needless scare will come from that.

Has [MENTION=16275]SteveW[/MENTION] contacted Mike D (@SteedaTech) and asked for help yet? Would be my first step.

The bolts breaking is not common - in the macro sense, it is rare. Just like, in the macro sense, it's rare that your AC unit will fail despite it being perceived as very common on this forum. Forums make it seem like it's happening to everyone and it's getting frustrating considering the blame seems to always be on Steeda, which has sold significantly more of these than BMR. Steeda's poly inserts actually fill more of the bushing than BMR's comparable offering, so in that respect they're more secure. Is it more likely with inserts, sure - that's logically obvious. Can it happen with a totally stock setup though, yes.

In all instances involving inserts that I'm aware of, either the bolts were shown to be loose (improperly torqued; i.e., one that didn't have an issue was loose so it is assumed the other may have been as well), the threads in the bushing were stripped due to overtorquing and therefore the bolt could never achieve proper torque, the driver wheel hopped the life out of their car and got mad when something broke (that's Ford's problem, not BMR or Steedas), and/or N-drop launched on sticky tires (that's racer boi's thinking their M/T production car should handle sticky tires from the factory). Steeda conveniently gets the "blame" by default of them selling so many of these. BMR's poly inserts aren't immune to this. And this doesn't mean that properly installed insert cars can't have issues. But, it's not actually common - relative to the number sold - when installed and torqued properly.

I went about 10K miles with the standard red inserts and supplied bolts and about 6 drag nights with god awful launches (because I just can't pull of a smooth launch for the life of me...) and numerous road course track days... and no issues. I upgraded to 9/16" through bolts and Steeda aluminum inserts for piece of mind (with very little NVH increase). The through-bolt suggestion was made on this forum by Kelly and tested about a year prior by Steeda (and avoided as a product because it increases NVH and requires dropping the IRS more than most can handle). Doesn't mean it would have never happened to me... just saying.

Ford, not Steeda or BMR, made an accountant's decision with the way they secured the differential to the IRS subframe - it's a weak point of the car and you can get upgraded bolts from either Steeda or BMR. Frankly the entire driveline of these cars from the output shaft to the differential has the refinement of a tractor and it's laughable that it has so much rubber, yet still makes sharp clunks right off the dealer lot.

 

[BMR Tech]

Through bolting does not increase NVH.

I've actually been called about this topic by another company and told this is NOT an issue, hasnt happened OR that it only happens when BMR parts are in the mix. L. M. A. 0.

I also have screenshots of early on when I was told I was spreading misinformation when suggesting people through bolt in random posts.

Our poly diff bushing (not inserts) kits had through bolts included in them well before I knew of many of these issues. We also provide through bolts standard in our poly diff lockout kits.

 

[CustomS550]

What would the thread size and pitch be of the stock bolts? Better yet, would you happen to have a link for that replacement front bolt? How about that sleeve for the rear you mention?

Thank you!

What I have people do on stock bushings, is I have them run a replacement front bolt with a large washer. This bolt will place the SHANK of the bolt INSIDE the center aluminum bushing sleeve on the stock bushings. The factory front bushings have a machined relief - which makes it easy to use a bolt with a longer shank.

I have a VERY hard time believing that some guy who likes to make cars go fast, can figure this stuff out and improve upon Ford's designs. So I am going to guess that placing the shear loads on the threads, and also having the threads exposed outside of this relief is done intentionally. That being said, not my style! I have a bunch of cars around the country testing my stuff and I have not single issue with durability - and several of those people broke/severely bent the stock bolts.

So anyways, here are some pics to explain what I do to make the system more durable in extreme applications.

The photo that really shares detail is the comparo, where the scribed mark (where the pen tip is) shows where the shear path is (where the bushing meets the diff)....and as you look to the right, shows where and how the OE bolt is positioned.

For the rear bushings, just a sleeve like I have shown above with a nice bolt works. The only way to make it better would be to drill the diff ears out.

 

[SteveW]

I dropped the whole cradle out of the car and got the diff out of it. The rear driver's side bolt was broken off about an 1/8" or so into the cover but I was able to easily extract it with one of those Irwin tapered extractor/drill bit kits, #5 I believe.

So, whew, at a point now to go forward.

 

[BMR Tech]

I dropped the whole cradle out of the car and got the diff out of it. The rear driver's side bolt was broken off about an 1/8" or so into the cover but I was able to easily extract it with one of those Irwin tapered extractor/drill bit kits, #5 I believe.

So, whew, at a point now to go forward.

Updates?

Sponsored