09 135 manual rear differential LSD questions

[Shaun135i]

Ok so I have a few questions, I am told that the rear diff on a 135 manual the final drive is welded in for whatever reason? But on the auto it's bolted in making swapping in a lsd into a auto diff far easier? My questions are after being told to just find a auto diff to make life easier I did some part searching and was thinking well why don't I get a BMW diff with a lsd? So I looked up the 1m diff and it cross references to the e90 e92 m3 diff? Are they the same diff? Would they swap in? Would the same theory be in effect would I need a auto m3 diff? Or a manual diff? And what other parts would I need if going that route? Thanks in advance guys!

[ErvGotti]

From what I understand, you'll need to swap the whole rear subframe and drive shafts to get the 1M diff to fit. Better off going aftermarket.

[Shaun135i]

Originally Posted by ErvGotti

From what I understand, you'll need to swap the whole rear subframe and drive shafts to get the 1M diff to fit. Better off going aftermarket.

Like I said I looked up the 1m diff and that part number is the same part number for the m3 diff so if that's the case the 1m has the rear subframe as the m3? That may be true I am not sure? Anyways I would be able to get a m3 diff very easily that's the only reason I am asking what all I would need thanks my cost for after market would be 300 for a auto diff then 1200 for the lsd then whatever it cost to install or my cost for a m3 diff with a lsd would be about 300 and whatever parts needed to install? So that's where I stand.

[Fakemike]

Here is a site that has info on ratios and welded vs bolted:

http://www.vacmotorsports.com/blog/3...no-lsd-really/

[Shaun135i]

Originally Posted by Fakemike

Here is a site that has info on ratios and welded vs bolted:

http://www.vacmotorsports.com/blog/3...no-lsd-really/

Thank you! Great info now I just need to decide what would be cheaper and more effective buying a m3 diff with lsd and parts or building my diff or getting a auto diff and build that. From numbers I have been looking at from least expensive to most this is what I come up with m3 diff and parts? But not sure how much or what parts would be needed and then auto diff built with lsd and then finally most expensive would be building my diff. Has anyone has any experience in using a m3 diff on a 135? I need to find out what all that entails and if it's worth it in the long run.

[MightyMouseTech]

Originally Posted by Shaun135i

Thank you! Great info now I just need to decide what would be cheaper and more effective buying a m3 diff with lsd and parts or building my diff or getting a auto diff and build that. From numbers I have been looking at from least expensive to most this is what I come up with m3 diff and parts? But not sure how much or what parts would be needed and then auto diff built with lsd and then finally most expensive would be building my diff. Has anyone has any experience in using a m3 diff on a 135? I need to find out what all that entails and if it's worth it in the long run.

If you have a manual, you can not use the auto diff. The auto uses a "small frame" diff while the manual uses a "large frame" diff. They are physically different in size.

To install the 1M diff, you will need the complete rear subframe with suspension and brakes. Not sure if anyone has figured out the rear parking brake with doing that swap, and you will need a custom driveshaft.

Cheapest option is to get a replacement diff from MFactory and just swap yours out. In the end, will probably be about 1/2 the price of doing the 1M swap.

[Shaun135i]

Originally Posted by MightyMouseTech

If you have a manual, you can not use the auto diff. The auto uses a "small frame" diff while the manual uses a "large frame" diff. They are physically different in size.

Cheapest option is to get a replacement diff from MFactory and just swap yours out.

Well that's not what they said they said the cheapest way would be to get a auto diff since its bolt on and just buy the lsd from them? Otherwise the other most expensive option is buying the built diff from them? But that still does not answer my question of going with the m3 diff because I still feel that would be the cheaper better option. No one has yet to offer thoughts on that. A m3 or 1m diff would cost me about 300 with a lsd and the rear subframe would be about 300 so that's 600 what else would I need? Thanks for your input tho. It just does not correspond with what mfactory told me less than 3 days ago. ? Odd.

[WhatsADSM]

You need M3 diff, M3 subframe, M3 axles, and you need a custom job on the driveshaft to shorten it a bit. You don't have to swap to the M3/1M rear knuckles/hub/brakes if you don't want.

That may or may not be any cheaper than simply having and aftermarket LSD installed into your pumpkin.

[Shaun135i]

Originally Posted by WhatsADSM

You need M3 diff, M3 subframe, M3 axles, and you need a custom job on the driveshaft to shorten it a bit. You don't have to swap to the M3/1M rear knuckles/hub/brakes if you don't want.

That may or may not be any cheaper than simply having and aftermarket LSD installed into your pumpkin.

Thank you very much so as for the drive shaft part is the drive shaft longer on the 1m also? Just wondering because I know lots of m3 parts were used on the 1m

[Shaun135i]

I will most likely go the Mfactory route after some discussion and researching and I just found out I know a vender for them so that should work out. Now the question to build mine or to buy one built by mfactory hummm.

[WhatsADSM]

Originally Posted by Shaun135i

Thank you very much so as for the drive shaft part is the drive shaft longer on the 1m also? Just wondering because I know lots of m3 parts were used on the 1m

If it's a manual you should be able to buy the 1M driveshaft. However my guess is that it is prohibitively expensive. Instead you can take your stock driveshaft to a competent drive shaft shop and they should be able to shorten it for much much cheaper.

[drwillb]

I'm in the process of rounding up parts for full M3 rear end swap as well as front end. There are several ways of getting an LSD into a 135 but I chose the swap for several reasons.

1. Cost. You should be able to buy a full M3 rear end and driveshaft for about or just over $2k. Don't try to piece it together as this will be much more expensive.
If you are really interested I'll share my parts source, a local guy that only dismantles M3s.

2. This will work for a manual 135 but not an auto because of gear ratios. The M3 DCT diff is a 3.15 which is just a small bit shorter than the 3.08 in our manuals. The diff from a manual M3 is just not a match at all for either manual or auto 135.

3. The full rear end swap will bring M3 brakes and all the rear links that we consider to be upgrades for our cars. Throw in adjustable toe links and it's an even bigger win.

4. The rear brakes will need to be balanced so that's why I went with a front knuckle, control arm, and brake swap as well. In addition, I bought the M3 booster/master to ensure proper function and balance.

5. The swap allows you to shop the forums for all sorts of brake and suspension upgrades at reduced prices.

6. Driveshaft. You will need the back half of the M3 shaft and the front half of the 135 shaft so that both ends mate up properly. The back half needs to be shortened so the entire thing matches 1M length. My buddy has a 1M so I'll be figuring out the exact length in the near future. (We're hybernating in the northeast right now)

7. The stock rear springs from the M3 do not swap over well. They are too long. I'm not sure about the front ones. I was lucky to nab Harold's stock shocks and springs from his 1M.

I've got a thread I started in the DIY section and I'll be updating as I go but I don't expect to be bolting up the subframe until late March or early April. In the meantime, it's time to clean the parts, replace 2 CV boots, and order everything I'll need. I have a spreadsheet I'll share when it's all done but the info on there is already pretty complete.

Bill ///M

[HP Autosport]

Originally Posted by Shaun135i

Ok so I have a few questions, I am told that the rear diff on a 135 manual the final drive is welded in for whatever reason? But on the auto it's bolted in making swapping in a lsd into a auto diff far easier? My questions are after being told to just find a auto diff to make life easier I did some part searching and was thinking well why don't I get a BMW diff with a lsd? So I looked up the 1m diff and it cross references to the e90 e92 m3 diff? Are they the same diff? Would they swap in? Would the same theory be in effect would I need a auto m3 diff? Or a manual diff? And what other parts would I need if going that route? Thanks in advance guys!

Welded because it is easier and saves BMW money.

Auto has a 3.46 vs your 3.08 and it's also a smaller case(weaker ring and pinion) not ideal for high hp and tq applications. You can get a Wavetrac 3.08 complete final drive ready to install from us for $1995, that is not a bad deal at all.

M3 is entirely different.

[titium]

Originally Posted by HP Autosport

You can get a Wavetrac 3.08 complete final drive ready to install from us for $1995, that is not a bad deal at all.

so between wavetrac, mfactory and quaife which would be your pick?

[AB M2C]

Originally Posted by titium

so between wavetrac, mfactory and quaife which would be your pick?

I have a quaife (manual) with a 3.46 final drive. Highly recommend. But I do hear really good things about the others. Honestly no matter what you probably will be happy.

[HP Autosport]

Originally Posted by titium

so between wavetrac, mfactory and quaife which would be your pick?

Wavetrac, Quaife, then the other guys in that order.

Wavetrac represents very high value and reliability. Quaife has been around a long time, but it's more money. All the time attack BMWs(Berk Technology, ER and us) ran either the Quaife or Wavetrac 3.46 sport ratio without a single issue.

[MFactory]

Originally Posted by HP Autosport

Welded because it is easier and saves BMW money.

Auto has a 3.46 vs your 3.08 and it's also a smaller case(weaker ring and pinion) not ideal for high hp and tq applications. You can get a Wavetrac 3.08 complete final drive ready to install from us for $1995, that is not a bad deal at all.

M3 is entirely different.

Actually, no. The Auto 3.46 is also available in the larger 215 housing.

If you purchase an MFactory, you have a choice of 2.56, 2.81, 3.08 and 3.46 off-the-shelf for the large 215 housing.

[MFactory]

Originally Posted by titium

so between wavetrac, mfactory and quaife which would be your pick?

MFactory, Wavetrac then Quaife, in that order.

Why?

For quality, you won't be able to tell the difference between them

For strength, ours have been proven to be stronger time and time again

For performance, ours perform better where it matters because we provide more torque/traction (higher bias ratio)

For price, ours is the lowest cost, whether just the LSD unit or a fully rebuilt pumpkin

If you want to pay more for less (other than brand name), then go for the others.

[HP Autosport]

Originally Posted by MFactory

Actually, no. The Auto 3.46 is also available in the larger 215 housing.

If you purchase an MFactory, you have a choice of 2.56, 2.81, 3.08 and 3.46 off-the-shelf for the large 215 housing.

All auto 135i's come with a small case.

[MFactory]

Originally Posted by HP Autosport

All auto 135i's come with a small case.

Yes, but he has a 3.08 MT, which means he can use the 335i AT pumpkin, which is available in the large 215

[HP Autosport]

Originally Posted by MFactory

Yes, but he has a 3.08 MT, which means he can use the 335i AT pumpkin, which is available in the large 215

It's not the right fit for everyone.

Increase in operating RPMs at cruising speeds and takes away a good 2-3 miles per gallon in gas mileage. Acceleration is great in middle gears, but a very short first gear makes it not ideal for day to day use. Excellent on the track when low to mid range gears are used.

[MFactory]

Originally Posted by HP Autosport

It's not the right fit for everyone.

Increase in operating RPMs at cruising speeds and takes away a good 2-3 miles per gallon in gas mileage. Acceleration is great in middle gears, but a very short first gear makes it not ideal for day to day use. Excellent on the track when low to mid range gears are used.

That wasn't the question nor answer though. You replied to him with an answer that wasn't true (i.e that he didn't have the option of a 3.46), so I simply corrected it

Which ratio is correct for his application is not in question here, and is something that he would need to research based on his needs/requirements.