I think I might have a problem...

[porsche735]

I was getting my transmission ready to take to the shop to get the differential setup and found this inside the differential housing:


Looks like a crack from the carrier bearing race to the bottom of the case. and maybe another one to the right of it. Here are some pictures from the outside:






Looks like a hairline, maybe for about 1/2", but then I don't see anything continuing the way it does on the inside.

What do you think? Is it a crack? If so, should I get it welded, or should I try to find a new case (this is a 1986 915)? If I need a new case, anyone have one with tight pinion and mainshaft races?

Thanks!
Chris

[Flieger]

Can you tell if it is raised or sunk in? The part on the outside just looks like a casting mark, but the inside view looks like a crack.

[porsche735]

It is slightly raised on the inside. Running my fingernail across it catches...

Thanks,
Chris

[RWebb]

use a scraper on it & see what you find

it can be repaired if need be

[Flieger]

If it is raised, it is a casting mark. It is where the sand mold got a small crack in it as the hot metal was poured in and solidifying. It is extra metal so the stress concentration is not much to worry about, but you could try to lightly grind/file it down.

[porsche735]

I took it to Jerry Woods and they suggested getting it dye tested (I guess the analog to magnafluxing for aluminum). Turns out the testing is about $100. So, I took it to a mil spec welding outfit to have a look. Yep, its actually 2 cracks. They said they could fix it for $85....wata bargin....and they do it right:

grinding out the crack
heating up the case
doing the welding
heating the case and allowing slow cooling

I am confident they know what they are doing and it will be done right...

Thanks for the feedback,
Chris

[Flieger]

Depending on the Silicon content of the alloy, it could overage in the regions which do not melt (welding) but are heated up and slow cooled. Heating a precipitation hardened alloy allows diffusion and growth of (fewer) precipitate particle size to occur quicker, making it brittle.

[nesslar]

Originally Posted by porsche735

I took it to Jerry Woods and they suggested getting it dye tested (I guess the analog to magnafluxing for aluminum). Turns out the testing is about $100. So, I took it to a mil spec welding outfit to have a look. Yep, its actually 2 cracks. They said they could fix it for $85....wata bargin....and they do it right:

grinding out the crack
heating up the case
doing the welding
heating the case and allowing slow cooling

I am confident they know what they are doing and it will be done right...

Thanks for the feedback,
Chris

Jeez, matching look on either side; I think you made the right move. And sounds very reasonable. Whew! Hope it's all good!