[AcmeExplosives]

Moderators...sorry, not quite sure where to post this w/turbo N54 motor. - Please move to the correct thread.
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I was reading a Tech Talk leter in Roundel where an E90xi guy was trying to figure out how to drain his rear gear fluid. He noticed there was no drain cock, weep hole, etc. According to Mike Miller (Tech Talk dude), and a correct assumption by the E90xi guy...there is no drain cock in newer rears and one must be drilled.

Mike goes on to explain some other (I was going to say features but...) facts about the rear. - not verbatim but...The rear is essentially disposable...at least on OEM stuff. If it goes...it will go and you just replace it with a new differential. Apparently, it's really not worth taking them apart and rebuilding them. - I guess not even worth tapping some threads for drainage.

Anyone out there that can confirm this..rebuke it...???
I'd like to hear what you think.

K

[Nyulak]

When you warranty an item, you have to take into consideration the cost of repair versus the cost of replacement. There are times when products at my work are replaced with a new item, because it would be cheaper and quicker to give the customer a new unit. We are pretty low-volume, so our differential between repair and replace is significant.

A mass-produced item will be relatively cheap to produce and the cost of the average repair coming close to the price of the original assembly. WHen you look at a differential, they are inherently robust, so when they fail it is normally catastrophic. There isn't too much to do to repair them. If it's just gears, you have to replace the gears. If the differential case is damaged, you can't just bang it straight with a hammer. With the quantities that BMW has with parts and the likelihood of failure, it is more cost efficient to replace a failed differential.

As for the long of a drain plug, this is true. I had an LSD installed by Koala Motorsport and the installation includes a new differential cover that has a drain plug. It's important for a clutch type differential to have a drain plug to allow for periodic fluid changes.

[stressdoc]

Yep. for most major components -- engine, tranny, final drive -- it's more efficient for dealer to pull whole unit out and replace it. Old unit is shipped back to factory for rebuild. Better than having dealer's service guys try to fix stuff that costs a ton to train them for, they might screw up, ...

Very few (none?) dealer mechanics have the skill and experience of someone like Brett Anderson at KMS with final drives.