e36 LSD question

[jRonin]

Okay, I know this question has been asked and/or answered, but searches on my phone get tricky and I haven't found the answer to my exact question, so any links or help would be appreciated..

I have a manual trans '96 328i vert. I want to put LSD in, and have a few local options available. I got a 3.38 diff from a '97 auto M3, but I'm being told my highway driving is going to suffer tremendously. Would I be better off trading it for a 3.23 from a manual M3 or will I still be suffering on the highway? Thanks in advance for any help on this!

[pbonsalb]

3.38 is great. Slightly higher rpm than 3.23, and M3 ran 3.23 rpm no problem. Look at hearing chart at diffsonline under technical. Plug in your tire size, try with your 2.93 and 3.38 and look at 5th gear 1.00:1 chart for highway rpm and mph.

[XnWarden]

I went from a 2.93 to a 3.23 lsd. I can still get 25-30 mpg cruising on the hwy. Not quite the 40 mpg i used to get.

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[pbonsalb]

There is usually a trade off — shorter gearing means higher rpm means worse mpg. Bigger motor means worse mpg. Hard to have it both ways.

[jRonin]

3.38 is great. Slightly higher rpm than 3.23, and M3 ran 3.23 rpm no problem. Look at hearing chart at diffsonline under technical. Plug in your tire size, try with your 2.93 and 3.38 and look at 5th gear 1.00:1 chart for highway rpm and mph.

That chart is actually quite helpful.. I like how they set it up as an Excel spreadsheet and I can review options a lot more clearly.. Thanks for this tip!!

[MParallel]

I didn't want my mpg to suffer, so I sources an 2.93 LSD for my 328i.

[pbonsalb]

Exceptionally few 188m 2.93 LSD in the US. And non LSD 2.93 is not easily modified because the LSD unit from a common 3.15 or 3.23 won’t fit.

MPG will be best with 2.93. Performance will be best with 3.38. You choose.

I had a 99 528i with 2.93 open and liked it as a comfortable cruiser with enough performance to get out of its own way. In my E36 M3, I have run 3.15, 3.23, 3.38 and 3.64 LSD. On the highway at 80, the 3.64 was not much fun but I liked it everywhere else. Made me want a 6 speed. The 3.15, 3.23 and 3.38 were all fine with the 5 speed.

[jRonin]

Exceptionally few 188m 2.93 LSD in the US. And non LSD 2.93 is not easily modified because the LSD unit from a common 3.15 or 3.23 won’t fit.

MPG will be best with 2.93. Performance will be best with 3.38. You choose.

I had a 99 528i with 2.93 open and liked it as a comfortable cruiser with enough performance to get out of its own way. In my E36 M3, I have run 3.15, 3.23, 3.38 and 3.64 LSD. On the highway at 80, the 3.64 was not much fun but I liked it everywhere else. Made me want a 6 speed. The 3.15, 3.23 and 3.38 were all fine with the 5 speed.

You lost me a little.. Aren't the M3 diffs almost bolt on replacements for the factory 2.93.. I thought the mounting was all fairly similar?

[pbonsalb]

I was referring to the idea of mating LSD guts from a common 3.15 or 3.23 LSD with the 2.93 gears you have. That does not work. You need a different LSD that is not common to fit 2.93 gears. E36 6 cylinder diffs are interchangeable but you may have to swap input flanges, which must be done right. Alternatively you can swap the rear half of the driveshaft if you can get one for the flange in question. But old shafts often have worn u joints or cv joints.

[MParallel]

I'm missing something as well. All 188 LSD clusters should drop right in any non-LSD 188 case.

2.93 is hardest to find as that's where the one with lowest production years.

[jRonin]

Think I'm going to settle on the 3.15.. Looks like the best balance for my needs. 2.93 lsd sounds difficult and/or expensive to source and 3.38 seems a bit aggressive for a daily driven drift car.

[pbonsalb]

I'm missing something as well. All 188 LSD clusters should drop right in any non-LSD 188 case.

2.93 is hardest to find as that's where the one with lowest production years.

You cannot find a 2.93 LSD diff in the US that will bolt right into an E36. So you have to make one. But you cannot make a 2.93 LSD using the gears from a 2.93 and the LSD from a commonly available 3.15 or 3.23. The lowest ratio gearset that will fit the commonly available LSD unit from a 3.15 or 3.23 is 3.07. A 2.93 gear set cannot be swapped in. You can go the other way — shorter (like 3.38, 3.46, 3.64, 3.73, 3.91, 4.10), but not longer (like 2.93, 2.79). And it’s hard to find the LSD that will work for a 2.93 — if you must do this, you will be looking at cars from the 80s or maybe the 70s or importing one from Europe.

I think a 2.93 LSD would be fun in a nicely done turbo E36. One with a responsive turbo and 400-500 lbs rwtq. When I was changing diffs to go shorter and shorter, my car was centrifugal supercharged and I always wanted more torque but the centrifugal could not give it so I settled for torque multiplication through gearing. Then I wanted a 6 speed to get the highway rpm down, but the conversion would have cost $2-3k. So I sold the supercharger and added the 6 speed money to the proceeds and installed a turbo. I had 500lbs rwtq and changed to a common 3.15 LSD.

I would have gone to a 2.93 but as I have explained, they don’t exist in the US and they are hard to make out of parts from other diffs. I have since changed to a stronger 210mm LSD diff (because I was breaking 188mm diff output stubs at the dragstrip), again in 3.15, and fortunately the LSD unit in the big diffs can take longer gears so I could now change to a 2.93. But as I was thinking about doing that change, I broke my second 5 speed trans so I am in the process of changing to a 6 speed that can take more power. With the overdrive of the 6 speed, I don’t need a 2.93.

[pbonsalb]

Think I'm going to settle on the 3.15.. Looks like the best balance for my needs. 2.93 lsd sounds difficult and/or expensive to source and 3.38 seems a bit aggressive for a daily driven drift car.

Doesn’t a drift car need to be responsive? I would think the torque multiplication of the 3.38 would be the best choice. I not a drifter but I read a little about them because they are hard on cars and find the weak points.

[spyderg0d]

I didnt get any mpg change when switching from 3.15 to a 3.91. In fact i saved city mpg. Gearings low enough that i can just about idle down the city streets in 5th at like 27mph. The quick gearshift to get from 2nd to 3rd to 5th is annoying. Still get 27 to 29mpg on highway going 55.

[AJLM34A]

Think I'm going to settle on the 3.15.. Looks like the best balance for my needs. 2.93 lsd sounds difficult and/or expensive to source and 3.38 seems a bit aggressive for a daily driven drift car.

Are you driving on the highway for long distances?

A 3:15 diff is most likely from a 95 or early 96 M3 and will have a 6 bolt input flange, your's should be a 4 bolt so you would need a drive shaft too or tearing down a diff or 2 to make it work.

I ran a 3:91 for a few months and was too many RPMs on the highway. I currently have a 3:73 and it is a blast, car flipping rips even with an automatic and my 5th gear is 0.74 vs 1.00 in a manual so it is okay RPM wise under 80 mph. I have a 3:64 from an X3 that I will be building soon.

Go with a 3:38. Get new bushings for the cover, new output seals and o-rings, (maybe a 3 clutch setup since it is just adding parts and throwing away a spacer) and good fluid for an LSD, not Mobile 1 since it does not have additives for clutches.

[pbonsalb]

Hard to compare the M3 automatic since it has OD. You can figure out the comparison by using the diffs online spreadsheet and plugging in 0.74 for 5th gear with the 3.73 and then figuring out the equivalent rear for a 5 speed manual with 1.00 5th gear.

[AJLM34A]

Hard to compare the M3 automatic since it has OD. You can figure out the comparison by using the diffs online spreadsheet and plugging in 0.74 for 5th gear with the 3.73 and then figuring out the equivalent rear for a 5 speed manual with 1.00 5th gear.

I will not be gaining much by much with the 3:64, but need the 3:73 for my 94 325i future track car.

For the 5-speed manual difference to the 5-speed auto, 4th gear in the slushbox is 1:00
Screen Shot 2019-05-14 at 5.09.36 PM.png

[westcoaster310]

I went from a 2.93 to a 3.23 lsd. I can still get 25-30 mpg cruising on the hwy. Not quite the 40 mpg i used to get.

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You are talking trash there is not one e36 on earth that gets 40mpg

[XnWarden]

You are talking trash there is not one e36 on earth that gets 40mpg

What about one thats driven downhill in neutral to school both ways? Checkmate atheists

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[Auto Parts Guy]

My 3.38 and 6 speed is perfect. Plus I get 53mpg.




JK more like 21mpg mixed.

[westcoaster310]

What about one thats driven downhill in neutral to school both ways? Checkmate atheists

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Bro just stop you are making it worse. Just tell the truth everyone knows ur talking trash

[blckstrm]

I've got a 3.38 w/ a 5 speed. Yes, it's worse than the 3.23, but not enough to care too much. It's not enough higher than you don't just get used to it.