i got a diff from a scrappy and i have noticed it has some very very fine fracture lines on it. is this normal or is it trashed?? there are no visable gaps. any information would help!

 

fracture lines on the outside? Sounds like the casing is knackered.

 

yes its on the outside. i was told it came of a car that had done 20k miles

 

it's a casting so won't have a smooth finish, sure it is fractures and not just lines on the surface. Best pic i can see of a close up here

 

When the diff 'blows' it's the casing that gives way - I don't know which bit specifically but it would be worth investigating further before fitting it.

 

Give it a really good clean and take it to your local engineering shop (Yellow pages should find one) Ask them to do a crack test on it. They'll probably be able to do a dye penetration test. Not infalible but a quick way to know. It should not cost much and you don't need to take the diff to bits. (although sealing up any vents is a good idea.)

 

thanks for the help guys. i just hope its the casting process that has left wrinkles in it!

 

It sounds like head cracking from the casting process but without seeing it i can't be sure. If it is it's just surface defect and not a functional issue.

SShort of getting it into work Aldfort's suggestion is probably the best way to be certain

 

hope you can see the lines that i am talking about

 

The only ones I can see are on the left hand side of the picture following the rib and then turning 90 degrees and heading in the direction of where the oils draining.

If you mean those ones they look very much heat cracks which will be surface only.

What happens is when the molten aluminium flows into the die. If hits the colder die wall and skins over. When the molten aluminium behind it comes in it starts to solidify too. Once the dies filled and the aluminium cools then the material starts to shrink as it cools. This can cause surface cracks and a kind of crazy paving effect. From the photo it looks like this is the case and shouldn't be a problem at all.

Crack detecting is the way to be sure though