I dropped my oil pan last week to install a new gasket, as the old one had a growing leak on the passenger-side rear, and had sprouted a couple more over time. Was losing about a quart of oil every 1500mi (with track driving).
Had some pretty bad rust around the level sensor and a few other places, and a bunch of the paint protection pulled off when I removed the gasket, so I sanded the bad areas down to the metal and sprayed some high-heat Rustoleum to seal it.
Repair was going well until one of the studs holding the oil level sensor snapped when I was torquing it down (at 30in-lb!).
Apparently, the oil pan on N51/N52s differs between automatics and manuals - the autos got an aluminum pan 11137552414, while the manuals (like mine) got a stamped steel pan 11137553164.
Unfortunately, my speed shop said that the steel was too thin to guarantee that a new stud would not leak, and even worse, the stamped steel pans are impossible to come by second-hand. New OE is $700+, and new OEM are $1600 for some reason...
I was able to source an aluminum pan from an auto for $150. However there are some differences:
These pans take the same gasket, but the aluminum pan is constructed a little differently, and has a large rear face which requires longer bolts. The auto bolt kit is 11132210959, and the manual kit is 11130396707.
EDIT: There is also an extra opening on the pan, which I believe is to allow for a crankcase vent return line, but my car doesn't have the line, so there is another drainplug made of plastic, part: 11137553165
I also found when attempting to install the new pan, that the cover plate over the bell housing of the transmission is different between the two. As mentioned, the auto oil pan has a rear face that butts flat against the bell housing, and there are three bolts that go through the bell housing to secure the oil pan against it, and hold the cover plate in position. These three bolts exist on the manual as well, but to hold the cover plate in position, the plate has three threaded nuts either cast or pressed into the plate. These nuts are about 1/4" thick, and interfere with the rear face of the aluminum pan.
My plan is to grind these nuts off, as the bolt holes line up from the transmission to the new oil pan, so I do not foresee any more issues. Will update the thread once it's all together. Lots of pain for a simple snapped stud...