e34 diff swapping need-to-know

[303e30]

Anybody know a good place to get a 3.46 LSD from a 535i. I want one for my 525i to replace my open diff 3.23.

[dgoodsy]

You could try the classifieds of this forum or local wrecking yards. Try googling 'bmw parts', I have heard a few good things about Bavarian auto recycling (www.bmrparts.com) and www.carparts.com although I have never used either.

[525gte]

I may even be easier to buy a 188mm ring and pinion off ebay and rebuild the diff you have . And while your in their add a clutch or 2

[Danni540]

Nice read! I've been thinking a lot about how to swap a 3.15 diff from a 750i into my 540i. And honestly what I've come across is that in order to do that I'll have to have my drive shaft customized, since the splines on the 540i shaft are bigger so I can't put a 750i flange on the back of my drive shaft. I think I'll be keeping my stock LSD.

I've also both parted out and replaced the diffs in several E34s and E32s throughout the years. The headache that this is causing for you guys in the US, is doubled here in Europe. We got the 518i, 518g, 520i, 525td and 525tds. That's where the real headache starts. All of these had different rear subframes. They had E28 style diffs. Four bolts on top off it and one bolt directly in the rear bushing. Except some M43 518i, some of them had the same differential as the 525i.

Here's an E34 525tds differential (click on the picture):


So, everything in the OP applies here, plus all the different types of drive shafts and differentials of the cars the US didn't get.

[eurokitsch]

Hate it because the gears are too short or is it a problem with the lsd and asc together?

Top speed is about 130 at 6800rpm crazzzy

[SpecRaceM5]

Great thread! Must add to bookmarks.

[dgoodsy]

Nice read! I've been thinking a lot about how to swap a 3.15 diff from a 750i into my 540i. And honestly what I've come across is that in order to do that I'll have to have my drive shaft customized, since the splines on the 540i shaft are bigger so I can't put a 750i flange on the back of my drive shaft. I think I'll be keeping my stock LSD.

I've also both parted out and replaced the diffs in several E34s and E32s throughout the years. The headache that this is causing for you guys in the US, is doubled here in Europe. We got the 518i, 518g, 520i, 525td and 525tds. That's where the real headache starts. All of these had different rear subframes. They had E28 style diffs. Four bolts on top off it and one bolt directly in the rear bushing. Except some M43 518i, some of them had the same differential as the 525i.

Here's an E34 525tds differential (click on the picture):


So, everything in the OP applies here, plus all the different types of drive shafts and differentials of the cars the US didn't get.

yes, i meant to add that into the OP that this applies to US vehicles, European market is different with all the variants stated above that we did not get here. I found a few differences in the european market that i didn't delve into, that would have made the whole topic twice as long and twice as confusing.

As for you wanting to swap the 750 diff into your 540, can't you just swap the input flange from your 540 diff onto the 3.15 diff and bolt it in? Or am i missing something.. or do you not want to mess with that? if it is changing the input flange, to be honest the people who have doe it speak pretty confidently that it isn't that tricky, it is the people who haven't done it that say not to.....that's what I have found.

Top speed is about 130 at 6800rpm crazzzy

aah makes sense, that's really revving at freeway speeds, you shouldn't have any trouble passing anyone at least!

[Danni540]

As for you wanting to swap the 750 diff into your 540, can't you just swap the input flange from your 540 diff onto the 3.15 diff and bolt it in? Or am i missing something.. or do you not want to mess with that? if it is changing the input flange, to be honest the people who have doe it speak pretty confidently that it isn't that tricky, it is the people who haven't done it that say not to.....that's what I have found.

Well, I have swapped the input flanges on diffs before, but that was 8 years ago and for my first BMW ever, a '94 525iA. That was no problem at all. There is this one guy living in the same town as I do that has a 540iA with an open diff and he wanted limited slip, so he bought one from a 735i and was going to swap the input flange but the 540 input flange was a lot larger in diameter in the inside, even though both diffs were the 210mm size.

I have had both the 3,15 750i drive I own and a 3,91 735i diff on the floor on my garage and apart from the ratio they looked identical. They could be bolted into each car without changing any flanges. So I'm just assuming the 540i input flange will be too large for the 750i diff, like it was for the 735i diff.

There is one other guy in my country who has put a 3,15 lsd from a 750i into his 6 speed swapped 740i, but I still haven't gotten in contact with him to ask how he did it.

[dgoodsy]

Well, I have swapped the input flanges on diffs before, but that was 8 years ago and for my first BMW ever, a '94 525iA. That was no problem at all. There is this one guy living in the same town as I do that has a 540iA with an open diff and he wanted limited slip, so he bought one from a 735i and was going to swap the input flange but the 540 input flange was a lot larger in diameter in the inside, even though both diffs were the 210mm size.

I have had both the 3,15 750i drive I own and a 3,91 735i diff on the floor on my garage and apart from the ratio they looked identical. They could be bolted into each car without changing any flanges. So I'm just assuming the 540i input flange will be too large for the 750i diff, like it was for the 735i diff.

There is one other guy in my country who has put a 3,15 lsd from a 750i into his 6 speed swapped 740i, but I still haven't gotten in contact with him to ask how he did it.

interesting, I wonder if that is a europe only variation that we avoided here on this continent, maybe something to do with the m30 large diff (which we didn't get)...I haven't heard anything of the sort.

[Stereoinstaller1]

Well i have been a reader on here for a while, i figured it was about time i contributed something of substance! good luck with the m54b30 swap, I was considering that for a while as well. Also what is your perfect 70mph cruising rpms?

I am hoping for roughly 2800 at 70, if that motor would have grunt to pull out of that. Tire size is part of the story too, I plan on 275/35/18s out back.

[dgoodsy]

I am hoping for roughly 2800 at 70, if that motor would have grunt to pull out of that. Tire size is part of the story too, I plan on 275/35/18s out back.

Thats about what I am aiming for as well, maybe a bit lower even. It is higher top gear rpms than the auto tranny and 4.10 that is in the car now but I am expecting fuel consumption to drop (in town) because there is another gear in between 1st and top gear, should make it easier to keep the engine where it is happy.
This is a cool site with a road speed calculator, as long as you know your transmission gear ratios you can figure out your exact road speed based on gear and rpm or vice versa.
Hot tip: If/when you change your tire specs press the 'GO!' button for it to change the diameter for you.

http://www.endtuning.com/gearratios.html

[zenn0ne]

The best write up by far thanx OP and the rest of the participants

[USDbeams]

Hey guys. I'm in the states trying to build my 530i for drifting. Came from nissans so just starting to learn about BMWs.

So my 5spd ratio is waaay to high for drifting but prior to finding this out I had the diff welded.. Do you guys think it would be cheaper to buy a ring and pinion on ebay(found 188mm 3.73 which i think will be perfect for $120usd) and have the diff rebuilt or to find a diff through classifieds? My girlfriend has a m20 525i auto(4.10 according to post on this thread. which i fear may be a little too intense) with a blown head gasket that I may be able to use as a donor. If I went that option what exactly do I need to take from that car? I read as much as I could but lack of sleep caused me to come out of my usual forum lurking and actually post lol. I'm open for any ratio 3.46-4.10 what ever is the more convenient of the bunch to swap into my 530i manual.
ANYTHING HELPS! haha
Thanks in advance! -Your friendly forum lurker.

[USDbeams]

BUMP. ANYONE IN HERE? in here... in here..(echoes)

[Hofmeister]

I'd check out a local junkyard and get a ring gear and pinion from there. Though you need one from a diff the same size as yours

[zenn0ne]

BUMP. ANYONE IN HERE? in here... in here..(echoes)

I believe the 410 is a direct swap to your 530i...I have a freshly rebuilt 3.23lsd with 40% lock= 3 clutch pack rather then 2...pm me if interested

[Mark185]

Hey guys. I'm in the states trying to build my 530i for drifting. Came from nissans so just starting to learn about BMWs.

So my 5spd ratio is waaay to high for drifting but prior to finding this out I had the diff welded.. Do you guys think it would be cheaper to buy a ring and pinion on ebay(found 188mm 3.73 which i think will be perfect for $120usd) and have the diff rebuilt or to find a diff through classifieds? My girlfriend has a m20 525i auto(4.10 according to post on this thread. which i fear may be a little too intense) with a blown head gasket that I may be able to use as a donor. If I went that option what exactly do I need to take from that car? I read as much as I could but lack of sleep caused me to come out of my usual forum lurking and actually post lol. I'm open for any ratio 3.46-4.10 what ever is the more convenient of the bunch to swap into my 530i manual.
ANYTHING HELPS! haha
Thanks in advance! -Your friendly forum lurker.

When I was shopping for a 3.23 LSD, I had a hard time finding one for reasonable money. I finally bought a good used one from Diffsonline in MA. I probably paid more than I should but it had a guarantee and I was in the Boston area for business and picked it up in person. Unless you get lucky, don't expect to find a suitable diff quickly. The desirable ratios were not common. I think it will probably be quicker for you to buy the 3.73 gear set and rebuild your diff. One thing you might want to look for is an E32 medium case 3.64 diff. I may have the exact number wrong but there was a gear set close to those numbers in the E32. It may be more common than the 3.46 and 3.23 E34 gear sets. The 3.46 was standard in the 535i 5 spd E34 and 3.23 came in the 525i 5 spd.

If you are in CA, there is a Bfc member in the SF area that has built a lot of diffs for race and street applications and is very knowledgeable about what will work. He is more of an E36/E39 guy IIRC and I think his forum name is Wanganstyle or something close to that. He helped me out several years ago when I had to change an input flange on my diff and did not know what I was doing. He could probably find what you want although I don't know what it will cost.

[wanganstyle]

for the 188mm units there are 2 offsets for ratios;

LOW ratio offset units:
2.65, 2.79, 2.93, 3.07

High ratio offset units
3.15-4.45

the geometry of the LOW and HIGH are not compatible; Best to just get the entire open 4.10 + weld it then stuff it in.

[demetk]

for the 188mm units there are 2 offsets for ratios;

LOW ratio offset units:
2.65, 2.79, 2.93, 3.07

High ratio offset units
3.15-4.45

the geometry of the LOW and HIGH are not compatible; Best to just get the entire open 4.10 + weld it then stuff it in.

Interesting info. Can you explain the geometry difference? So I wouldn't be able to swap my 2.93 gear set into my 3.23 LSD?

[dgoodsy]

Interesting info. Can you explain the geometry difference? So I wouldn't be able to swap my 2.93 gear set into my 3.23 LSD?

http://www.bimmerdiffs.com/blogs/bmw...ifferent-gears

I believe that is what Wanganstyle is referring to.

[wanganstyle]

Interesting info. Can you explain the geometry difference? So I wouldn't be able to swap my 2.93 gear set into my 3.23 LSD?

to requote my prior post:


LOW ratio offset units:
2.65, 2.79, 2.93, 3.07

High ratio offset units
3.15-4.45

Physically the High ratio and LOW ratio sets are NOT interchangable; the geometry is DESIGNED to NOT be compatible by BMW.

[Binjammin]

to requote my prior post:


LOW ratio offset units:
2.65, 2.79, 2.93, 3.07

High ratio offset units
3.15-4.45

Physically the High ratio and LOW ratio sets are NOT interchangable; the geometry is DESIGNED to NOT be compatible by BMW.

I think he understands what you mean about interchanging, but isn't clear on the difference in geometry. For instance, is the ring gear more offset on one diff than the other?

[demetk]

I think he understands what you mean about interchanging, but isn't clear on the difference in geometry. For instance, is the ring gear more offset on one diff than the other?

Right, I was curious about the physical differences between the two.

- - - Updated - - -

http://www.bimmerdiffs.com/blogs/bmw...ifferent-gears

I believe that is what Wanganstyle is referring to.

Thanks very much, that explains it. So much for my 2.93 swap idea.

[wanganstyle]

I think he understands what you mean about interchanging, but isn't clear on the difference in geometry. For instance, is the ring gear more offset on one diff than the other?

yes the geometry is different. not sure how to explain it more clearly - No reason for me to give incorrect info.

low ratios have an offset of X
high ratios have an offset of Y

X is not = Y


one can download the dimensions and data sheet from Quaife website if you really really really want to know the EXACT numerical difference; this really doesnt help though.

if making ghetto welded for drifting just do it;
use the open that matches the gear desired - Open diffs are $0 and come already attached to the gearset.

if one is welding then we all know what is happing to the car.......

[TIRAX]

The e34 540ia e32 740ia shaft halves use the same centerbearing as the manual. So propably they just mix whit the manual. Also the 740ia and 540ia rear halfs are same lenght.