all right heres my sorry attempt at a right up

3.15 to 3.46 rear diff swap on a E46 sedan
I did most of this swap by myself but I highly recomend have a a extra set of hands to help. its also much saffer.
I got my 3.46 diff out of a 02 auto at a junk yard for $300. when purchaseing one make sure to check that its is good working order. if you spin the front that both sides move and there's no binding. check for cracks. check the threads on the front bolt mounts for damage.

tools needed
socket wrench
extenion socket
E12 star socket
13mm socket
20mm socket
14mm hex head socket
13mm wrench
18mm wrench
20mm wrench
breaker bar
torque wrench
floor jack
jack stands
wheel chocks

also needed
one 3.46 rear diff
two quarts 75w90 gear fluid
fluid pump
and one E46

the long process
first start by chocking the front wheels. then jack the rearend of the car then place jack stands under the car and lower the on to them. remove the floor jack to give you some room.
now with the car in the air start taking out the rear axle bolts. you will need the E12 star socket and a breaker bar to loosen them. I found that useing the e-brake to stop the axles from spinning. If you have a helper you might have them set and release when you need to gain access to the next bolt. prevents trips from under the car to the e-brake (that sucked and ate up alot of time).
http://a453.ac-images.myspacecdn.com/images01/88/l_4d79b428eab1fd34e384f5b086fa9124.jpg (http://viewmorepics.myspace.com/index.cfm?fuseaction=user.editAlbumPhoto&albumID=642876&imageID=9763222)
after removing the axles move on to the the driveline there are four bolts and they are also E12 stars. if you look at the heat shield you should she a hole inwhich you can put the socket and the extenion to reach the bolts to remove the drive line. use your helper to put the car in gear to loosen the bolts have them take it out to spin it to gain access to the other bolts.

now with the axles and the driveline bolts removed you can start the hard part. first I applied slight preshure to the bottem of the sway bar then useing the 13mm socket and the 13mm wrench loosen the sway bar. it should be able to move freely forward and back. then loosen the rear exheust bracket.

now use the 20mm socket with breaker bar and the 20mm wrench and loossen and remove the not off the bolt holding the rear of the diff in place. make sure to leave the bolt in at this piont. take the 18mm wrench to the front of the diff and loosen the two front bolts you can see them in the picture.
http://a206.ac-images.myspacecdn.com/images01/84/l_abdb224e4a02086823c4cb1e634d0505.jpg (http://viewmorepics.myspace.com/index.cfm?fuseaction=user.editAlbumPhoto&albumID=642876&imageID=9763279)
now support the diff with the floor jack. once its supported remove the rear bolt. now procede to loosen the front to bolts you wont be able to remove them from the brace but they should back the diff out. these two bolts will take a very long time.

now that the rear diff is loose and supported by the jack the fun part will begin I suggest haveing someone there to help. first push the front of the diff up and toward the drivers side. then let the jack down slightly the diff should lower alittle and rest on the swaybar. then lift on the rear of the diff and slide the swaybar back toward the rear. pull the rear of the diff toward the passanger side it should fall out on to the jack you and your helper should control this to prevent injury on damage to the car or diff.
at this point you it should look like the picture above.

if I were you I would take a break have a cold drink and compare the two diffs to make sure that everything is correct.
http://a683.ac-images.myspacecdn.com/images01/113/l_6c6d99884f7b41a4a544b9bc6735aeda.jpg (http://viewmorepics.myspace.com/index.cfm?fuseaction=user.editAlbumPhoto&albumID=642876&imageID=9763245)

okay to make the install of the new diff alittle easier I recomend draining the fluid out before hand this can be done by the the bottem plug and using the 14mm socket. you can use this DIY thread to help. http://www.bmw325i.net/maint_rear_diff_fluid.shtml

after draining the diff place it on the floor jack postion it under the gapping hole that is your rearend.
http://a514.ac-images.myspacecdn.com/images01/123/l_0980564903f4befd752fbba26c079519.jpg (http://viewmorepics.myspace.com/index.cfm?fuseaction=user.editAlbumPhoto&albumID=642876&imageID=9763293)
http://a440.ac-images.myspacecdn.com/images01/86/l_684e1c7dd40420202c159a088330fa3f.jpg (http://viewmorepics.myspace.com/index.cfm?fuseaction=user.editAlbumPhoto&albumID=642876&imageID=9763302)

now useing your helper first lift the front of the diff into the front driverside. then jack the diff up slowly. make sure to have the rear of the diff toward the pasanger side. once you have the diff approximtly above the spot where the sway bar normal rests slide the swaybar under the diff. aline the front of the diff with the front two bolts this will be hard but you can do it. tighen the two bolts down. then push the rear bolt through and tighten the nut down. now once both are in place torque them down. the front bolts should be torqued to 70ft-lbs. and the rear bolt should be torqued to 128ft-lbs

reinstall the swaybar I was unable to find any spefic torque on the exhuast mount or the swaybar mount so I tightend the as tight as I could.

with all the main bolts in place you can start putting the axles and the driveline back in be repeating the same process you used to remove them.
axle bolts should be torqued to 61ft-lb and the driveline bolts should be torqued to also 61ft-lbs. after all of that it should look like this
http://a796.ac-images.myspacecdn.com/images01/72/l_4cf10c4da12267bba2c01568c465d9f3.jpg (http://viewmorepics.myspace.com/index.cfm?fuseaction=user.editAlbumPhoto&albumID=642876&imageID=9763319)

after that putting the gear oil in is easy using the 14mm socket remove the fill plug. use a fluid pump and pump the gear oil in.

http://a472.ac-images.myspacecdn.com/images01/115/l_386903012ea768f6fc46fe728c501f3f.jpg (http://viewmorepics.myspace.com/index.cfm?fuseaction=user.editAlbumPhoto&albumID=642876&imageID=7604990)

after filling and tighting everything up you can jack the car up with a jack remove the jack stands lower the car back to the ground remove the jack and wheel chucks. and drive the car around warming the fluid up.

after the all of this you have installed you 3.46 diff know go have fun.

ive been looking for the upgrade to a 3.46 diff all the ones that are applicable for my car are open diffs, i havent found LSD for that application. I would have a custom one made but im looking at a lot of money. How do you like yours?

with the 3.46 what are your rpms at 80 in 6th?

Would a 3.91 be a good fit for the 330i six speed?

ive been looking for the upgrade to a 3.46 diff all the ones that are applicable for my car are open diffs, i havent found LSD for that application. I would have a custom one made but im looking at a lot of money. How do you like yours?

I like mine alot a LSD would be nice but unless your tracking the car its not a must I leave my DSC on while driveing hard and it keeps the inside wheel in check

with the 3.46 what are your rpms at 80 in 6th? NO 6th for me

Would a 3.91 be a good fit for the 330i six speed?
yeah that might make first way short. but I have heard of people swaping x3 diffs in

How is the torque now with the change. Does it help off the line. I am asking because I want to do the same thing to mine but have never got an opinion on how it effected their cars performance. Mine has A AA twin screw, headers and exhaust. This is about the last thing I can do but I want to make sure I get something out of it.

What does this acualy do and what is the stock differential?

How is the torque now with the change. Does it help off the line. I am asking because I want to do the same thing to mine but have never got an opinion on how it effected their cars performance. Mine has A AA twin screw, headers and exhaust. This is about the last thing I can do but I want to make sure I get something out of it.
well as far as the 0 to 60 its to close to tell but the car feels alot stronger. in third gear the car pulls so much better.

What does this acualy do and what is the stock differential?
think of it like a ten speed in first gear its very easy to move the bike but you cant go very fast. and in tenth gear it is very hard to move the bike but you can go very fast. so to put it a simple a higher gear ratio is like droping from tenth gear into nineth so its easier to pedal with a decent top speed.

as for the gear ratio stock for my car (2001 325i 5 speed) was 3.15 and for a 2001 325i auto it was 3.46 so buy swaping a 3.46 dif into my car I have a higher gear ratio makeing it easier for my car to turn the wheels but I lost some of my top speed so instead of being able to do 163mph my cars top speed is now 151mph I dont think I need to go that fast.

Thanks for the info /\ I'm very interested in this but what are your rpm's in 5th at 80?

^ right around 3500rpms I think I dont tend to look at my speedo when Im driving at a high rate of speed.