Has anyone ever experienced a ring gear bolt shear in the rear differential? Truck has 54,000 miles. 2017 F-150, 3.5 Ecoboost, crew cab, 6.5 bed, max tow, 3.55 ratio.
Ring gear bolt sheared off and flung itself out of the differential. Simplest fix appears to be a replacement axle from the junkyard.

 

I haven't seen this before. I'm curious, any idea what sheared the bolt head off?

 

That's the big question. No answers as of now. Diff has never been opened. Possible over torque from the factory? Possible hairline fracture in the bolt when new? Still an open question with no real answers.

 

Look at the photo!
The Bolt seperated from over torque or fatigue of some cause.
It is clearly not a Shearing action by failing so deep in at the parting surfaces. The surface clearly shows the metal crystallization seperation surface straight outward and is not from a Shearing action. The Ring Gear did not/could not rotate against the carrier to cause any Shearing ..side-wise on the bolt body.
Let's stop calling every failure a Shearing failure when it is not that kind of failure.
Same thing happened with the Axle issue bolt issue and just kept being called a Shearing
Nit picking but let's be accurate about things in posting, where possible, when it can be plainly seen.
Good luck.

 

So you are saying torsional shear stress lol. So the bolt sheared……

As a follow up per a Dana axle engineer I had review the photo.

”Appears to me the bolt was overtorqued from the factory. Ring gear bolts unfortunately are already close to yield when installed. When overtorqued torsional shear stress is introduced to the bolt. Overtime no real time frame the bolt will fail causing the bolt to shear just as in the picture.”

 

I think some one needs to look up the terms for Bolt shear strength and Tensile strength.
They are not one and the same.
The direction of failure is 90* different, in direction.
Tensile failure is along the Axis of the Bolt for sepersation limit failure, as the photo shows.
Shear is 90* side ways, a "sliceing" action to the Axis. I do see not that in the photo. The Ring Gear cannot move to cause any shearing with all the rest of the Bolts still in place.
.
I sure didn't make this up.
Good luck.

 

The bolt failed in tension and it appears from the photo that there was a small existing crack at the root of one of the threads which extended for almost a complete thread length (360°). The crack reduced cross-sectional area in that region. Cyclic loading of the bolt due to normal vehicle operation propigated the crack, further reducing the cross-section until the the tension force overcame the tensile strength of the bolt and it catastrophically failed. The tension was from the torque applied to the bolt. It may not have been over-torqued. As mentioned, these bolts are torqued to a high level so initial tension is high and does not allow for much section reduction before failure.

If the bolt failed at the first complete thread (just bellow the shank) then this would increase the likelihood that the bolt was over-torqued, but would not be conclusive in that diagnosis as the crack could have existed at that location from the fastener manufacturer rather than being started by an over-torque.

The breaking of the bolt likely did not damage the housing initially. The evidence of the broken bolt being hit by the neighbour bolt head is what likely propelled the broken bolt into the differential housing causing that failure.