Boxer differential failure

I was accelerating onto the highway, heard a clunk, and then saw black smoke billowing from the rear of my Boxer. After I stopped, I could see oil dripping from the tranny where the left driveshaft connects. When I took the transmission apart, I could see the left flange that carries the left differential bearing, had cracked, see picture. The differential had also cracked apart where it was welded together, see picture. Because of the cracked parts, getting the broken differential out took quite some time, as the quill shaft had been pinched by the broken flange and wouldn't move.
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Situation normal -- the weld in the diff carrier breaks and then the irregular angled surfaces move against each other "ramping" apart = breaks the structure holding the bearing outer race.

 

It happens, that is why many have replaced welded diffs.

 

What year and mileage ?

 

this is more typical for TR´s.
as I always say: the question is not if it will break, only when
but sorry to see this
what about the crwon gear? also damaged a little? on the photos still look ok

 

Sorry for what just happened to you, Nelson.
Glad I preemptively changed the differential on my Testarossa 3 months ago.

 

You could reach out to Newman and see if he has a billet diff that might work for you.

 

A known problem with no way to predict when it will happen. Like earthquakes.

Hopefully the repair process goes smoothly. GT Car Parts has the side covers machined from billet.

 

Nelson, you seem to be handling this a lot better than I would.

Surprised this happened on a Boxer. I'd be very curious to know what mileage the car had. Or maybe what tires were on the rear. I thought this was more prone to happen on the more powerful cars (TR).

 

Good day Robert,

Given the past threads on here, a number of Boxers also suffered a similar fate... and so it is not uncommon at all.

Cheers,

Sam

 

My car is an '84 with about 75k miles. The crown gear was fine.

 

the new diff
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I had to re-shim the flanges/bearing carriers to get the right clearances
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the transmission had been rebuilt in the early 2000s, so I assumed the differential had been replaced then. Silly me.

 

you are very lucky

re-shim is normal to get the right result

where you got an other cover from?

 

I second Sam ....+1

There are many stories on F-chat of "cream-puff" / lo-miles Boxers of all variants that the weld gives out and causes surprisingly light damage (like just the carrier, and somehow everything else was fine), to OMG / sick feeling for the parts hunt for precious, rare, and very expensive hardware needed to sort out. The connection to the failure and resulting damage is not necessarily a direct correlation. Some bad events occurred at low speeds etc.

I couldn't stand it knowing, or rather not-knowing I might just take the car out on a beautiful day for a coffee etc, and have this thing break. I replaced it and now feel much better about taking her out.

Maybe others can chime in as to predictive things linked to the failure like car was built on Tuesday etc ?? I just don't know and gathering that data is unlikely at best.

BTW: Is that a hockey puck holding the diff in position for the photo? Awesome !

 

Two lines on a graph. One is how well welded that specific carrier was. The other line is the totality of high stress events in the life of the carrier. One is always an unknown. The other is in all but a very few cases an unknown.

Good luck predicting failure.