Broke Diff Cover

[reelizmpro]

you think corteco puts crap versions out for aftermarket only?

Although I can't say for sure it's the case here (OE BMW parts haven't been that high quality these days) ...OE BMW part versions are typically subjected to stricter QC standards and only the best parts qualify. The rest are offered up as OEM parts. OEM parts offer the same function at a lower price, however, sometimes depending on the part...the parts aren't as good as OE BMW. It could be a minor blemish or a critical flaw. For example, Laso water pumps for the S14 many years ago were known to leak. Many people experienced the same problem so now only OE BMW Laso's are recommended. It could have just been a bad batch but who's going to take a chance overheating their S14 to find out?

[LowR3V'in]

Interestingly, when looking for a diff bushing I noticed parts houses were blowing Corteco's out for $20 each while OE BMW Corteco's were still 3-4x the price. After some research I found that people were having the same problem with the bushing being slightly oversized and cracking diff covers. I opted to go with the Powerflex diff bushing for $40.

you think corteco puts crap versions out for aftermarket only?

[LowR3V'in]

i bought some cortecos for my e36 cover.
they were slightly slightly too big so the metal around the bushing pealed back like lead.
luckily the metal was very soft and the cover was ok with it.

it seems like the rubber is softer then the oe but maybe it's because of the old rubber dried out.

[reelizmpro]

Interestingly, when looking for a diff bushing I noticed parts houses were blowing Corteco's out for $20 each while OE BMW Corteco's were still 3-4x the price. After some research I found that people were having the same problem with the bushing being slightly oversized and cracking diff covers. I opted to go with the Powerflex diff bushing for $40.

[jeffnhiscars]

Corteco is OEM but nothing surprises me any more. I had mine pressed in by my machinist who probably has a more delicate touch.

[Five5peed]

3x the roundness error and a larger nominal diameter
As an engineer, this doesn’t surprise me. What does surprise me is there is not THAT much difference between the two samples...just enough to take it over the edge.



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[muppetman342]

It was an aftermarket bushing, Corteco to be specific.

I posted up about this problem on the r3v facebook page, to which multiple other people came out saying they had the same issue with Corteco diff bushings.

I called FCP telling them the story to which they immediately covered the cost of the used cover I bought on eBay and shipped me a new BMW bushing at no charge. They also pulled the Corteco bushing from the site, pending investigation of this issue. FCP is the real MVP here, seriously, who else would pay to replace a 28 year old part that I didn't buy from them!? Any other company would have laughed at me and told me some bs about me being an idiot and not knowing how to use a press. They gave me no fuss, and made the situation right. Love them so much.

Anyway, I took some measurements when I had both the Corteco and BMW bushings in hand: interestingly neither is perfectly round, I found the Corteco one to be 3.338" at it's widest point and 3.328" at it's most narrow, the BMW one is 3.324" at it's widest and 3.321" at it's most narrow. When pressing in the BMW bushing, it went in with noticeably less effort and didn't break my diff cover, so I'd call that a win.

tl;dr Don't buy a Corteco diff bushing, it will destroy your diff cover

[AndrewBird]

Cast aluminum inherently has stress in it, so the gap isn't all that surprising.

Was it a stock bushing or aftermarket?

[muppetman342]

Alright guys, here's a new one: I'm pressing in a new diff bushing, got it in ~99% of the way, then *plink* and this happened: https://photos.app.goo.gl/hGp82M2pB2wzgDhP7

The fact that it's still gapped with the bushing now removed makes it seem like that piece was already under stress. I wonder if I tweaked it when removing the old bushing or something?

Anyone else had this happen to them, have a diff cover for sale (already got a post up in the classifieds), or have any advice on how to avoid this when I inevitably do the same job on the new diff cover?