325ti Differential Help

[tctwnd]

Hello all. I currently have a ti with a 92 325i engine swap. This was done a while ago by someone else. The car runs gfreat, and I have a 3.91 (i believe) diff in the car. The diff is not limited slip, and revs a bit too high for my taste. I want to throw in a 3.25 or similar ratio LSD. I still have the ti subframe, any idea which diffs will fit my car without more mods? Would a 3.25 LSD form an e28 5 series fit? I have a line on one from an 84 533i. Another line on a 3.45 LSD made for an e30 4cyl that. any input would be really appreciated.

Thanks,
Ben

[cali-ti]

large case diffs are going to be a tight fit (need to mod the diff mounts on the car and hammer the trunk floor subframe a bit), but they do work. the 3.73 from an e30 is a common swap. you'll need an e30, z3 6-cyl or m-coupe diff cover that has the single diff mount. the e30 4-cyl diff is most likely a small case diff and would fit, just a question of the power handling capabilities.

[cali-ti]

Thanks for replying about the diffs. I have a non-stock diff in there now, 3.91. I did not do that swap, but how can i tell what car that diff came from and if my half-shafts or flanges were modded? I am sorry for all the quesitons, just branching into the e36 world.
the question is, what size is your current diff? believe the stock ti diffs were 3.45 (manual, open and limited slip) and 4.44 (automatic), so it must be from something else, just not sure what. forget if the e30 had a 3.91 diff. do you have any pics of the install? might be easier to tell from that. i'm guessing it's a large case diff, but it should be much easier to tell from pics :)

[tctwnd]

do you have any pics of the install? might be easier to tell from that. i'm guessing it's a large case diff, but it should be much easier to tell from pics :)

I will take pics tonight when I have the car jacked up. time to put on the snow tires. perhaps even a little late...

[cali-ti]

hehe ... my car hasn't moved in more than a month and i chucked my 3 year old snow tires in the trash (recycled them actually) before i moved to denver this summer. i could take pics of anything though, it's up on 4 jack stands :)

[tctwnd]

here are the best i could do in my work parking lot with my camera phone. prob will need better, let me know if you can tell anything.

hehe ... my car hasn't moved in more than a month and i chucked my 3 year old snow tires in the trash (recycled them actually) before i moved to denver this summer. i could take pics of anything though, it's up on 4 jack stands :)

[cali-ti]

gotta be a small case diff, it looks so tiny! ;)

here's mine (large case with m-coupe cover): http://www.318ti.org/gallery/showphoto.php?photo=965&size=big&cat=500&ppuser=1131&sortby=d&sorttime=999&way=asc

[tctwnd]

this means i need a 4cyl diff, either e30 or e36, correct? A 6 cyll. e30 will not fit without mods. Will a 320is diff fit?

[cali-ti]

there are a few mods, but it's not too bad. there has been a large discussion around whether or not you need to change the halfshafts, but i'm willing to say you don't now (whether you WANT to is something else). you'd need to move the ti diff flanges into the large case diff. you might get away with only having to grind the diff mounts coming down from the floor pan on the ti to get the large case diff to fit. it's tight. you might need to hammer the points where the top diff cover bolts would hit the beam in the floor of the ti (i ground mine away and wish i'd hammered at it instead - if/when i learn to weld, i'll fix it up somehow). otherwise, as you said, a small-case diff would work. the e30 diff should bolt right up with no changes. so should a z3 4-cyl diff or a ti 3.45 LSD.

EDIT: see the pic i posted a link to above. those are the areas i had to mod to get the large case diff to fit. the mount on the left has a counterpart on the other side of the diff cover.

[tctwnd]

the e30 diff should bolt right up with no changes. so should a z3 4-cyl diff or a ti 3.45 LSD.
this is only the 4 cyll. e30 diffs? or also the 325is? I am just unsure which cars came with large diffs and which came with small ones.

Ben

[cali-ti]

the 325 has a 6-cyl and has the diff that i now have in my car (3.73 LSD large case diff).

[ClubSport]

There are small, medium, and large diffs. The 318ti came with a small 3.45 (manual) or small 4.44 (auto). I put a medium 3.25 from an m coupe (6 cyl) into my ti last winter. I had to pound the floorpan of the trunk up about an inch in one spot and grind away a little on the diff mount "ears", plus put in half shafts from an e30 6 cyl car. I did not want to mess with putting 4 cyl half shafts into a 6 cyl diff, although some have done it, it is weaker that way.
So that's what you're up against.

[cali-ti]

plus put in half shafts from an e30 6 cyl car.
did you try the m-coupe halfshafts and they wouldn't fit or did you not have those to try?

[ClubSport]

Didn't have those to try, and got the e30 ones cheap.

[cali-ti]

Didn't have those to try, and got the e30 ones cheap.
damn. i was hoping you'd have positive or negative info on whether those work or not. i'd like to get a set of reman'd halfshafts and would like the biggest ones possible. i might go with z3 3.0 coupe shafts as it appears the e30 flanges i bought new are the same size as the inner (diff side) mounts of those. i'm hoping the ABS rings are the same size as the ti so i can remove my ABS sensor shims i had to make.

[ClubSport]

I had to backspace my sensors too. Forgot about that, but it's only a washer's thickness. I calculated the difference in diameter from the stock ones to the e30 ones and used 1/2 that number for the washer thickness.