E31 Convert Open Diff to LSD

[wolfebrian2120]

Hi All,
Has anyone gotten one of the 3.64 diffs converted to LSD? I have a spare diff and would like to give it a try. My understanding is is that it just needs a different carrier. I would prefer to keep the existing gear ratio if possible. If someone knows a good shop that would do the work I would consider shipping it out to them. I know there are a lot of different types of LSD out there. I just don't know if anyone still makes parts for our size diffs. Some of the supposedly differential shops I found online haven't returned any of my emails.

[8eights]

https://diffsonline.com/bmw-e31-840-...l#.XpYSp_1KiUk

[petejk]

Hi All,
Has anyone gotten one of the 3.64 diffs converted to LSD? I have a spare diff and would like to give it a try. My understanding is is that it just needs a different carrier. I would prefer to keep the existing gear ratio if possible. If someone knows a good shop that would do the work I would consider shipping it out to them. I know there are a lot of different types of LSD out there. I just don't know if anyone still makes parts for our size diffs. Some of the supposedly differential shops I found online haven't returned any of my emails.

To buy a 210mm 3.64:1 LSD from diffsonline is $1899 for M-variable, and $2899 for a traditional 2-clutch ZF LSD (this includes core charge).
I've seen a few other shops online, and prices are similar.

To convert your existing 210mm open diff to LSD, the parts are available to buy, but it's the installation that anyone apart from a good shop will almost certainly screw up.
This video shows what's involved - https://www.youtube.com/watch?v=F7QTGKCcWVU
I spent a few hours researching my options at the weekend, and here are some links:

You'll need to choose your LSD type. The parts below would convert your 210mm 3.64 open to M-variable LSD. The majority are from a company called racing diffs, which I am using for clutch discs for my diff refresh.

Used M-variable LSD from an E46 M3, priced from $325 plus on ebay.
https://www.ebay.com/itm/BMW-2001-20...l/323673536843

Clutch plate rebuild kit $300
https://www.ebay.com/itm/BMW-E46-M3-...f/264439754559

Input/Output seals, bearings, and crush washer is $250 or so
https://www.ebay.com/itm/Differentia...5/264096677215

Shim kit $150
https://www.ebay.com/itm/Differentia...3/263582624045

Diff rear cover gasket
https://www.fcpeuro.com/products/bmw...33-33108305034

***************

The ZF LSDs don't seem to be widely available to buy used. You pretty much have to buy a whole diff, the most plentiful seem to be the 3.15LSD from the E32. They go from about $1250
https://www.ebay.com/itm/Bmw-Large-Case-Lsd-210mm-3-15-Diff-Bmw-E32-34-36/372957861585

This matches almost exactly with the extra $1000 that diffsonline charge for a diff with a ZF LSD.

***************

In my case, owning a 6-speed, the 3.15:1 LSD is a great upgrade from 2.65:1, and I will be installing new clutch plates, swapping the input flange and installing new input and output seals, which I should be able to do myself.

[Hyper]

...a company called racing diffs, which I am using for clutch discs for my diff refresh...

Me too, took a gamble on an eBay'er from Serbia.
My disc pack just arrived, super fast.

Didn't realize that everyone has heard of them 'cept me.
They seemed to have exact knowledge of my limited edition MBZ.

Great vid, they also posted one of a LSD swap in.
On their website, nice to see a library of ring & pinions.

***
Re: clutch vs helical...
Did a conversion, clutch to helical on my Aerostar, to remove the issue of clutch degradation.
A helical does not wear out (ed: in a 100K miles).
However, my understanding is that on icy surfaces, helical reverts to an "open" character while a clutch will hang in there.
Not an issue where I am, and otherwise works quite well in rain.

Comparo, shown with Ford gearing. Helical by Eaton.


***
Owner DIY?
I've been through two (ed: overhauls).
You'll need that hydraulic press shown in the vid along with right-sized mandrels.
If you do it yourself, you'll know if someone screwed things up, rather than just being told it was perfect as usual.

MBZ 185 on a 10 ton Northern.


Checking gear mesh pattern.

[m6bigdog]

Hyper, I feel your pain..
I did a couple of ring & Pinion gear changes (4.56:1) with LSD. Made a hauler out of a small truck. Must have done it right - lasted over 150k miles!!

The guy in the youtube video made it seem way too simple!!

The most important requirements.
1) Set the pinion depth:
If you are reusing the gear set the pinion depth should be good when you re-install the correct shims behind the pinion gear inner race. You will want to check the ring/pinion wear pattern to make sure.
New gear set; this can be done with a factory tool or trial and error; install the pinion with shims (start with shims old gear set) and bearings with slight preload and set the ring gear back-lash and check the ring/pinion gear wear pattern...repeat with different shims behind the pinion gear inner race.
Yep pull the pinion inner race to change shims. PITA for sure and time consuming to get it right cause you will do it several times if your lucky!!!

2) Set pinion bearing preload:
This requires pinion shim pack and a new crush distance-piece between the pinion bearings.
Need inch-oz/ dial torque wrench. Torque pinion nut to minimum value, check preload. too much preload? add shim(s); too little preload? increment torque until preload is with in range for bearing used.
Pinion preload also needs to be done when a different yoke is installed during a diff swap. Guessing doesn't get it!!

3) Final Setup:
Set ring gear back-lash and recheck the ring/pinion gear wear pattern. Hopefully your done!!

Ignore any of these setups and the diff ring/pinion will not last and the gears will whine!!

[wolfebrian2120]

Hi guys, Thanks for the input. I think I will try to build it myself. Luckily my brother is a machinist so I can get him to help press stuff in place. I didn't realize the e46 m3 used the same size differential. That is good to know. I'll let you know if I have any trouble.

[TxGR8White]

Quaife can build you one for around $1800-$2000 (last time I looked). 3.64 LSD
Supposed to be super bullet proof. Give them a call: 714-424-9400

*no affiliation

[m6bigdog]

...I didn't realize the e46 m3 used the same size differential. That is good to know. I'll let you know if I have any trouble.

The E46 diff is the same gear set but the case has different mounting points so it would take a lot to make it usable.

[tepescovir]

https://www.schmiedmann.com/en/bmw-E...oduct=33928336

Don't know if everything needed is included, but they say it will be matched by your vin number as 3 types available

[Mikekugel]

Hi All,
Has anyone gotten one of the 3.64 diffs converted to LSD? I have a spare diff and would like to give it a try. My understanding is is that it just needs a different carrier. I would prefer to keep the existing gear ratio if possible. If someone knows a good shop that would do the work I would consider shipping it out to them. I know there are a lot of different types of LSD out there. I just don't know if anyone still makes parts for our size diffs. Some of the supposedly differential shops I found online haven't returned any of my emails.

Get ahold of Jim Blanton / Performance gearing Tucson AZ. He built the LSD a few years back, and it has been flawless.

[wolfebrian2120]

Hi petejk, my brother and i are trying out the LSD conversion. A couple of issues.

1. The racing diffs clutches in the E46 carrier are pretty tight. We are thinking of leaving out the free play thrust washer.

2. It seems the axle shafts that came with the donor diff are the same size. For the e46 carrier, im gonna need a longer and shorter one. Using the open diff flanges wont work. Any ideas where to get the right output flanges? Part numbers?

[dragon850]

M variable e46 m3 lsd will require the output shafts also, so you will need a complete differential.

[petejk]

Hi petejk, my brother and i are trying out the LSD conversion. A couple of issues.

1. The racing diffs clutches in the E46 carrier are pretty tight. We are thinking of leaving out the free play thrust washer.

2. It seems the axle shafts that came with the donor diff are the same size. For the e46 carrier, im gonna need a longer and shorter one. Using the open diff flanges wont work. Any ideas where to get the right output flanges? Part numbers?

I ended up rebuilding a 3.15 LSD from an E32, so I don’t have any hands on experience with the E46 LSD. But what dragon850 says, that you’ll need the flanges from the E46 diff, makes sense to me


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[TTTXGreg]

Get ahold of Jim Blanton / Performance gearing Tucson AZ. He built the LSD a few years back, and it has been flawless.

He did the one in my turbo when I changed ratio. All is good here also.

[rharris99]

Get ahold of Jim Blanton / Performance gearing Tucson AZ. He built the LSD a few years back, and it has been flawless.

He also built a 3:64 LSD for me a few years ago and it was the best upgrade that I did for my car. Also, he is a cool guy and I haven’t had any issues with my LSD.

[wolfebrian2120]

Ok yeah that makes sense. I wasn't sure that the M3 used the same axels in the rear as the E31. I ended up finding a pair of output shafts from some ex bmw mechanic on ebay. He confirmed that they were what I needed. Kinda weird there aren't any part numbers associated with them. But they are the right length and have the right bolt pattern. So it all looks good. right now we are just waiting on a special torque wrench to crush the pinion thingy.

[Arsenic]

I bought mine off ebay assembled about 5 years ago with a e46 M3 guts. Made a little noise on 3 point turns for a couple days. Its been fine for +50,000 miles.