Diff bolt sheared?

[TimJM]

I was working on my car again on Saturday and came to separate the diff to fix the leak and noticed this:


See the bolt centre top - should that be a bolt head there?

What is really odd (and doesn't really show on these photos) is that the head of what is there is really smooth and well formed. It doesn't look like a head has sheered off at all. It also has what looks like machined marks on the head - 10-15 perfectly round circular marks like tree rings on a trunk. THese look like machine marks and I can't image a sheared head would look like this:


I don't have any bolt extractors and I don't want to start separating it unless I can finish the job and refill the diff with oil. Should this be a bolt head here and if it should be then what has mine got in it and how to I get it out?

[pmessling]

I think that is a locating dowel, so its okay.

[pmessling]

Although looking at a photo of mine when i resealed it mine doesn't have it

[TimJM]

That's kind of reassuring...I was hoping it was some sort of dowel/peg for location. Although the fact yours doesn't have one makes me wonder if this has been modified for some reason.

[pmessling]

doesn't look like a mod because of how the cover has been cast. but if the cover can't be moved then you'll need to get it out.

[TimJM]

You're right. This is a 98 car and I see yours is an 04. Perhaps they changed the diff cover? I wonder if your diff casting has a hole the other side or if your diff is different too?

[Tanguero]

My diff has a dowel in that position so I don't think you will have a problem.

[TimJM]

Tanguero said:

My diff has a dowel in that position so I don't think you will have a problem.

Great - that's what I wanted to hear!

I will get on with splitting it and resealing then.