Rear Differential Support Bracket SNAPPED: Pics Added

[Shoppinit]

Meh, polybushes are a can of worms. I went OE bushes on mine.

[subtacex]

might be on suspension not on support bracket

[LunarWolf]

I must be going mad cos i'm 100% CERTAIN i replied to this late last night!... hmmmm...

it went a little something like this:
Thanks Shopinnit!

Nobby: They have a scissor lift, so no. They wouldn't have lifted it with a jack. (and if they did, they use a flat-headed type, which wouldn't have left the same wound.

DavePerc: Thanks! ... I agree it's been there a while. As mentioned, the edge of the wound was caked in road dirt similar to that of the rest of the perimeter of the bracket. Hence it looked like a manufactured notch until i cleaned it up to see the "bare" ( unoxidised) ally. To answer your question of the discolouration: well... kind of, yes.... it seems to be a small (3mm) black dot near the end of the bracket where it meets where the notch meets, I'll take photos tomorrow>... (see below, as it is now tomorrow!) Incidentally... i did not know that re stress fractures, so thanks! Is it just aluminium that happens to or any metal?>

Mavada: You'll have to refer back to Bam about that! But i doubt it. Probably just the angle. MRC don't make noob mistakes like that!!!LoL

Subtacex & ahooga: I did originally think about the road debris train of theory, but the chink is taken from the rearmost part of the bracket, to the rear of the car, so whatever it was would have had to bounce and hit the precise part and i just can't see that happening! (Unless of course it was done driving BACKWARDS at great speed!!!)
Well... it IS a manual conversion.. maybe they put the box in back to front and it had 6 reverse and one forward speed!!! LoL

And then, i decided i was being too silly for such intellectual persons such as yourselves, so i went to bed!

Today: here are the pictures. Only 2 this time!
Side view, looking longitudinally down the bracket, both sides, as if i've folded it "open" at the split:
See it makes the "3E" image. The notch is at the bottom: on the end of the lower "feet" of the shortened "3" and "E"
Are my "speech marks" annoying "you"??? hehehe.



And this photo, the same, but with the flash on and my lovely assistant pointing at the blackened mark with a biro on the right ("E") Visible on the "3" too, but i can only afford one pen!



PolyBushes: I've had some really <beep> ones on cars when i first started modding vehicles.... and have had some EXCELLENT ones. they really are hit and miss..... a LOT more research has to go in to them before i make a strong advisory verdict to be honest. But that's a WHOLE other thread for another time!

Thanks for your input and interest, lads!
Mitch.

[ahoooga]

Are my "speech marks" annoying "you"??? hehehe.

Noooo .......................but your extra large size font is

[Daveperc]

OK - I'm not a metallurgist, but I have looked at quite a few broken metallic objects as an engineer over my lifetime....

There are, IMHO, possibly three stages to this failure. First something took the bite out, and in the process left a small crack at the root of the missing bit - that's the "C" shaped dark area at the end by the missing chunk. It's dark because the surface slowly oxidised.

In the second stage that crack fairly rapidly propagated across most of the "E" shape. I really can't tell from the photo's (or possibly even from the object itself) if this took place instantaneously, or over a relatively short period of time (eg a few days/weeks). The surface looks very clean and smooth, and I can't see any evidence of limited oxidation on it. It could be that this cracking occurred whilst the car was in the workshop, possibly if on stands in the wrong place or oddly loaded for some reason

In the last phase the unit failed and broke by bending/ripping the top leg of the "E" - this is evident from the change in fracture surface for this area - it has much more pronounced"lumps" in it.

Having said all that, it's hard to tell from the photo's as shadows etc can easily mislead - for example there are some dark areas at the top of the "E" which might be evidence of earlier cracks/oxidation, and several other dark spots that might suggest it was just a crap casting!!

All of which may be vaguely interesting, but doesn't alter the fact that you need a new part - fast!!

Dave

[saulcupra]

i did think it looked like a clean break and therefore a bad casting (casting by nature introduces air into molten metal if done badly)

I would of said an abnormal load across it would cause the failure, accentuated by missing chunk which probably did cause a stress fracture

[subtacex]

+1

[LunarWolf]

Ahooga: Sorry, mate! I'm suffering from Hay fever at the mo quite bad, and i increased the size for my own benefit when reading through oin Preview mode, but forgot to change it back!!! (yes, twice, i know!)

Daveperc: That seems like a pretty spot-on analysis! I think the top part to which you refer is due to the fact that it was the last bit to break so was (pretty much) still connected when we took it off, as the bolts were still holding it on. The CV joint gave way so the diff or bracket didn't have to, if that makes sense!

Not convinced it was a bad cast: It's been on the vehicle 11 years and has taken some playing with!
Also, when the guy launched it (which is what i presume), he said it set off the ASC, (or whatever Audi calls it!) which may have created the imbalance fortified by the notch.

CV joint arrived from Deutchland yesterday so that'll go ion tomorrow! Yay!

Thanks guys! It's been an interesting discussion!