Small case to Large case Diff

[Dave]

How much trouble is it to do this swap, or can it even be done?

I am looking at an M10 318 to buy, but it has a small case open diff, and I want to upgrade.

[Dave]

No one here knows????

[DanGillan]

you just need to swap axles and output flanges.

[Dave]

Cool - that is not too bad, then, Thanks.

[Dave]

What about on a late model 318i? Is the diff swap straight up or do you have to replace output flanges and axles on it as well?

[DanGillan]

should be a straight swap

[mikeedler]

you dont have to change anything but the diff. the axles will work on both diifs,going from large to small, not 100% on the other way around.

[JRowe]

I have a 91 318is small case 4.10 LSD. I'm going to be replacing it with a large case 3.73 lsd when I do an engine swap. What else is needed? Can the same axles/flanges be used or will I need to change them as well?

[Xmarksthespot21]

I have a 91 318is small case 4.10 LSD. I'm going to be replacing it with a large case 3.73 lsd when I do an engine swap. What else is needed? Can the same axles/flanges be used or will I need to change them as well?

This question was asked a few posts up. You need to change nothing except for the diff. Axles/flanges will not need to be changed.

[KangamangusDriver]

A problem I am encountering is going from a small case diff to a large case. I pulled the diff out of my m42 (3:91lsd) and noticed the rear cover needs to be swapped due to the mounting bracket on the rear of the diff.

I am swapping in a 3:25 lsd from an E28.

I am assuming I will need a rear cover from a large diff E30?!
Does this sound right?

As far as the axle flanges the bolt pattern is the same, but are they different lengths? Do they need to be swapped from large diff to large diff?

Any Ideas, thanks!!

[fabianyee]

if the big diff is from another E30 then need not change anything.
but from an E28, that'll be a different story. the E28 output flanges are different from the E30. the rear cover is different as well..

all u need to do is the replace the E28 rear cover with one from a E30 big case diff and oso the output flanges..

Cheers...

Left E34 output flange, right E30


is ur diff like this?

A problem I am encountering is going from a small case diff to a large case. I pulled the diff out of my m42 (3:91lsd) and noticed the rear cover needs to be swapped due to the mounting
bracket on the rear of the diff.

I am swapping in a 3:25 lsd from an E28.

I am assuming I will need a rear cover from a large diff E30?!
Does this sound right?

As far as the axle flanges the bolt pattern is the same, but are they different lengths? Do they need to be swapped from large diff to large diff?

Any Ideas, thanks!!