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Differential Bushing finally failed...

AlbertD

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Noticed clunking in the rear at low speeds (10-15mph) over rough patches of road so checked the rear suspension and noticed the driver side differential bushing to have significant damage. The car has 51k miles and over 25 hours of hard track time so I'm guessing the repetitive heat cycles from track abuse may have lead to the failure.

I searched online at Ford parts sites and it doesn't look like they sell the OEM bushing separately. I would have to buy the entire sub frame. Ugh...

I'm torn whether to replace with a poly or aluminum bushing. I'm leaning towards the aluminum option from BMR since the car is 80% track 20% street and NVH isn't necessarily top priority, although if I could avoid it that would be a plus. Poly would provide less NVH, but would it stand up to the track abuse (high heat) or will it eventually fail like the factory bushing did?

Anyone else had their bushing fail from repetitive track use and if so, what did you end up replacing them with? Happy with your decision?

Picture of the damaged differential bushing:
49003499536_fa7fe2ec93_b.jpg
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JohnD

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I have black bushings in my diff, BMR steel lockouts and CBR05 on the cradle and the rear gear howl is phenomenal! Can't imagine what it would be like with aluminum ones. I actually have grown to like that sound, it varies with throttle and sounds real racecar-ish!! Simple things....LOL! This stuff was all put in when the car was new so the stock bushings are undamaged.

For aluminum, I dunno did not try them on the rear end. But I replaced Steeda motor mounts with BMR motor mounts and with the black aluminum pucks they were completely unlivable on the street, poly was much more reasonable though still way more NVH than stock.

My car is only street driven to get to and from the track or maybe to bed brakes, but even that was too much with aluminum inserts in the motor mounts. I was seriously concerned the vibration was going to cause major issues with fasteners loosening and components getting rattled to death. But that was motor mounts, diff may not be that bad.
 

BmacIL

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Unfortunately, they fail because Ford put a 2 mm oversize sleeve in it compared to the bolt. It can only take so much shock loading. The first thing I'd tell a new S550 owner to do is get the Lethal extreme hardware upgrade kit, and push the sleeves provided into the rear bushings. This creates a correct size condition and no more uncontrolled shock loading from the oversize.
Screenshot_20191103-130827_Chrome.jpg
 

BmacIL

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To the question: I would do through-bolting and poly bushing inserts.
 
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AlbertD

AlbertD

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Thanks for the feedback.

I did quite a bit of reading and I am leaning towards getting the Poly bushing replacement for the diff (BMR BK049), it also seems to address the other issue you bring up Bmac. While the sub frame is out I plan to also install BK048 (delrin cradle bushings) to eliminate any movement in the cradle. Looks like some folks have found out that if you spray Great Stuff (foam) into the sub frame that it helps mitigate some of the NVH incurred from the diff so I plan to try that out as well
 

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AlbertD

AlbertD

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Installed the BK048/BK049 combo this weekend

All the low speed clunking noises I was hearing before are completely gone. There is certainly new NVH from the bushings, but it was a lot less than I expected. There is now some pronounced clunks in between shifts which I imagine is the driveline slop. It is surprisingly loud, but... I can live with that. I can also hear the exhaust a tad more.

The improvement from the bushings is night and day. The rear end feels a lot more communicative to me and doesn’t wiggle over road irregularities like it did before. Zero wheel hop. Powering out of a corner feels WAY smoother which is an enormous improvement for me. The rear end is just overall completely planted.

Cant wait to see how it feels out on track.
 
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shogun32

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I went with the Whiteline diff bushings (70 shore) so a bit softer than either the BMR or Steeda alternatives, and also half the price. Ford needs to be forced to recall every diff and at minimum install a correct sleeve. Just unforgivable engineering F'up.

I used the CB010 for IRS stability.
 

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I went with the Whiteline diff bushings (70 shore) so a bit softer than either the BMR or Steeda alternatives, and also half the price. Ford needs to be forced to recall every diff and at minimum install a correct sleeve. Just unforgivable engineering F'up.

I used the CB010 for IRS stability.
Which one? KDT933 or 934?
 

shogun32

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Which one? KDT933 or 934?
933.
For the EB car I might just do the fastener fix ($29?) for the moment. But I do have another 933 and also Steeda kit which likely need a new home.
 

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I noticed mine also failed during my pre-weekend safety check a few months ago. I was starting to get some bad wheel hop during launches and shifts so that explains it. I run F-Street so I'm going to have to get the whole subframe replaced. My car had about 29k when it failed.The car had close to 200 autox runs on it at the time also.

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nrm101

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I noticed mine also failed during my pre-weekend safety check a few months ago. I was starting to get some bad wheel hop during launches and shifts so that explains it. I run F-Street so I'm going to have to get the whole subframe replaced. My car had about 29k when it failed.The car had close to 200 autox runs on it at the time also.

69703791_427475214841235_4392483175540981760_n.jpg
Looking for some feedback / advice ... i started hearing a clicking sound from the rear of the car, gone thru retighten everything and confirm all aftermark parts are good and installed to spec, I have Peddlers Coilovers height settings 1" lower than factory, and Steeda IRS Subframe Bushing Support and alignment sleeves. here is my drivers side sub frame-bushing the car has 9k miles on it?? i haven't tracked the car, yet at all , just typical spirted driving, and pzero tires .. is this possible cause of the clicking, and will just get worse, should i push for Dealer warrenty fix even with the after market parts installed?

Would bolt insert solutions out there prolong its life? or just do a steeda / bmr replacement now?

I have quickJack but not sure there is enough clearance to get the subframe out without true lift...
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shogun32

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Would bolt insert solutions out there prolong its life? or just do a steeda / bmr replacement now?
at the minimum shim the bolt - I haven't made the inserts, so just buy the $35(?) grade12 bolt kit.
Otherwise you can do the Steeda/BMR "puck" solution but it'll make a fair bit of noise. I highly recommend the Whiteline replacement bushing solution instead. PITA to install since you have to cut the dumbass OEM part out but it's practically silent. Plus it's cheap compared to the aforementioned. You just pay for it in labor and hassle.
 

TeeLew

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Those look interesting. The most interesting of which are the subframe inserts that are very similar to the CB010 but composite instead of metal. Should perform similar function with less impact noise.
I used to use their bump rubbers, but they said they had a factory fire which killed the machine which made the ones I liked the best. They were never available again. It was really good stuff, though.

The reason I was looking at them was exactly what you just mentioned. Metal subframe mount bushing are a no-no.
 

TeeLew

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Very interesting indeed. This stuff + the Superpro arm bushings could make for a somewhat competitive and legal STU car. The 285 width max hurts the Mustang though.
Those cars you mentioned only get 265, for whatever that's worth.
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