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2Addicts | BMW 2-Series forum Technical Topics N55 (M235i) Engine, Transmission, Exhaust, Tuning LSD with FD change

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      10-31-2019, 02:09 AM   #1
goodNIGHT
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LSD with FD change

I'm going to get the M perf LSD around next April and I'm thinking of additionally swapping in a 3.46 final drive from the M2

What I gather is that the LSD is sealed and you cannot swap out the 3.077 final gear.

So my only options are to buy from Diffsonline, Quaife or get a wavetrac LSD and add the 3.46 FD??

Last edited by goodNIGHT; 10-31-2019 at 04:39 PM..
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      11-02-2019, 07:56 PM   #2
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Theoretically you could swap in a different gear, but it would be far cheaper to buy from Diffsonline.

I too considered the 3.46 gear, but keep in mind that the overall diameter of the 19 inch tires used on the M2 are nearly 1" taller than the M235 18" tires. That means the M2 gearing is more like a 3.23 on the M235, all things considered. Meaning, running a 3.46 on an M235 with the stock height 18s would be like running nearly a 3.7 gear. To me, it sounded like fun and would make the car really responsive. However, these cars make a lot of torque, especially tuned, thus aren't remotely as dependent on torque multiplication like an a high revving NA motor. I ended up going with the MPerformance LSD (3.08 FD). I like the longer gearing as I find it more tractable with a tune. Plus, I saved about $1200 going with the MP LSD over something from Diifsonline.
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      11-03-2019, 03:01 AM   #3
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I like the 3.46 FD in my Wavetrack a lot! Not because of torque multiplication although its nice too. The 3.46 allows you to move through the rpm range, hear the terrific engine and high rpm sound. All while commuting. I like it best when the summer tires were almost worn. And least with winter tires at 245/40. Means I could probably go higher than 3.46.

Speeds are so slow in the US that the drive ratio change is no problem. If I were on the autobahn I wouldn’t do it .

What I would like is a seventh gear. Or change the ratio just of the last, sixth gear in the manual gearbox. This would help a lot for long stretches of highway driving. Must be very costly or near impossible. Anybody come across it?
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      11-03-2019, 11:45 AM   #4
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So i had to look at some other cars and compare.
I listed the FD and looked up the drive wheel tire diameters, then standardized the FD ratio to tire size. So the M235i is still set up to be a daily cruiser than sports coupe.
Last two columns are the Hp/Tq FD multipliers. * sorry i wrongly swapped the hp and tq columns*
Really illustrating how our FD does not exploit our power. Our cars lag greatly behind the other sports cars.

A 3.46 ratio would bump us up to 1107/1141 hp/tq. But we'd still be behind the other cars in this group.

And yeah exactly - I don't think its so much about torque multiplication anyway, as so much as staying in the power band and especially increasing throttle response.

I can see both of your points - The M LSD is cheaper, is clutch type and it wont negatively affect resale. But the lockups % and less aggressive make it limited.

The Wavetrac is reliable and offers more aggressive gearing. But it is more expensive and I wonder who will buy this car with a 3rd party LSD???
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      11-03-2019, 01:48 PM   #5
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Just keep in mind the power curve. NA motors and high strung 4 banger turbos rely heavily on torque multiplication to get into and stay in the powerband. An N55, especially a tuned one, had a very broad torque curve which means the torque compensates for the lack of gearing and it allows for less shifting in a track situation.

On a drag strip, I doubt a deeper gear set will make much of a difference. It will certainly feel faster by the seat of the pants.

I think the 6MT N55 M2's gearing feels perfect and it's effectively a 3.2x compared to my M235's 3.08. I just couldn't justify the cost over the MP LSD. Plus a clutch based LSD, especially the one built by Drexler for BMW, is so damn good for the street and light track duty. Lockup percentages are perfect. They are more aggressive than you'd think. Totally changed the car.
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      11-03-2019, 02:14 PM   #6
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In the above clip I'm on buttonwillow here in SoCal. I'm behind a CTR, mustang GT and 991.1 Porsche. On the first right hander you can see how much they pull out from me. It frustrating bc I just can't do anything about it. They must be pulling at least 1 second just in that one turn. That turn is taken in the low 30mph range. I was hoping to dig out of there with a quicker FD. There's one more turn on track that's complete LSD dependent.
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      11-03-2019, 02:17 PM   #7
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Quote:
Originally Posted by XutvJet View Post
Just keep in mind the power curve. NA motors and high strung 4 banger turbos rely heavily on torque multiplication to get into and stay in the powerband. An N55, especially a tuned one, had a very broad torque curve which means the torque compensates for the lack of gearing and it allows for less shifting in a track situation.

On a drag strip, I doubt a deeper gear set will make much of a difference. It will certainly feel faster by the seat of the pants.

I think the 6MT N55 M2's gearing feels perfect and it's effectively a 3.2x compared to my M235's 3.08. I just couldn't justify the cost over the MP LSD. Plus a clutch based LSD, especially the one built by Drexler for BMW, is so damn good for the street and light track duty. Lockup percentages are perfect. They are more aggressive than you'd think. Totally changed the car.
In the end I might just go with the M per LSD. It's cheaper and I wouldn't have to worry about selling the car.

So many limitations on this car 😩
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      11-03-2019, 10:53 PM   #8
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Its not a giant change with the M compared to my wavetrac. I am sure you will be happy. My other BMW spins to 14600k and I just changed the final drive ratio - I guess I like high rpms

For me this is all about fun versus cost. Compared to costly carbon pieces you get a lot of improved fun for street driving. Just saying.

Its a manual, those are desired and a non M LSD is probably not a big issue for selling. Tuning the engine is more of a concern for me if I would get a used M235i. Just my thoughts.
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      11-04-2019, 11:19 AM   #9
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Quote:
Originally Posted by goodNIGHT View Post

In the above clip I'm on buttonwillow here in SoCal. I'm behind a CTR, mustang GT and 991.1 Porsche. On the first right hander you can see how much they pull out from me. It frustrating bc I just can't do anything about it. They must be pulling at least 1 second just in that one turn. That turn is taken in the low 30mph range. I was hoping to dig out of there with a quicker FD. There's one more turn on track that's complete LSD dependent.
You will be pleasantly surprised at the difference. It's massive. Instead of having the backend step out and slide and lose momentum, slides will be harder to come by and when they do happen, you aren't losing momentum. The back end is far more planted and you can really hammer it out of the turns. It use to think this car needed more rear tire. It turns out it just needed an LSD. I'm on 245/35R18 MP4S tires (square setup) and it's absolutely perfect.
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      11-05-2019, 08:34 AM   #10
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is it at all possible to fit an m2 diff to the 235/135? i have seen one at a breakers yard for sale
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      11-05-2019, 12:33 PM   #11
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is it at all possible to fit an m2 diff to the 235/135? i have seen one at a breakers yard for sale
It wont. I was thinking about that earlier too
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      11-05-2019, 12:50 PM   #12
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Quote:
Originally Posted by XutvJet View Post
You will be pleasantly surprised at the difference. It's massive. Instead of having the backend step out and slide and lose momentum, slides will be harder to come by and when they do happen, you aren't losing momentum. The back end is far more planted and you can really hammer it out of the turns. It use to think this car needed more rear tire. It turns out it just needed an LSD. I'm on 245/35R18 MP4S tires (square setup) and it's absolutely perfect.
Yeah im starting to get excited about upgrading. Its about time.

Ill be running a final baseline run at the end of january at Buttonwillow. Then install the LSD and compare lap times, sector times, and feeling impressions in March

While I've conceded to getting the MP LSD, i know Id get better performance from the more aggressively geared Wavetrac.
There is a reason why the Mustang PP1 is given a 3.77 FD and 275/35 rear tires over the standard GT.

Regardless, im guestimating about 2 seconds in lap time reduction with the LSD. I really hope
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      11-05-2019, 01:04 PM   #13
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Lol I just noticed the specs on the new M2 CS are 3.73 FD and 444hp, R:265/35 F;245/40 tires
Im sure the M2 guys are gonna try to snatch that FD for their own cars
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      11-06-2019, 12:04 AM   #14
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Just have mine installed today. I am really excited. Try to take it easy for 500 miles. I 'll post feedback after that.
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      03-23-2020, 11:48 PM   #15
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Quote:
Originally Posted by Wishxuuu View Post
Just have mine installed today. I am really excited. Try to take it easy for 500 miles. I 'll post feedback after that.
Cool. Looking forward to hearing your impressions. Any clicking or grinding noises so far??
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      04-02-2020, 04:12 AM   #16
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Quote:
Originally Posted by Wishxuuu View Post
Just have mine installed today. I am really excited. Try to take it easy for 500 miles. I 'll post feedback after that.9Apps APKVidMate APKVLC Download

Still waiting!!!

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      06-19-2020, 06:52 AM   #17
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that's great looking forward...
vidmateteatvshareit

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      11-11-2020, 01:36 PM   #18
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Does anyone know if the F30/F32 MP LSD will fit our cars? They are on crazy deep sale right now and I'd love to get one if they will fit. Also, are there major differences between 6MT and ZF8 other than gear ratio? If the housing, input shaft, and output shafts are all the same this should theoretically work with the M235i/M240i. jiofi login forpc
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      11-11-2020, 03:07 PM   #19
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Quote:
Originally Posted by xpaceten View Post
Does anyone know if the F30/F32 MP LSD will fit our cars? They are on crazy deep sale right now and I'd love to get one if they will fit. Also, are there major differences between 6MT and ZF8 other than gear ratio? If the housing, input shaft, and output shafts are all the same this should theoretically work with the M235i/M240i. jiofi login forpc
Won't fit. They run different spline axles. Others on this forum have tried.
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