Manual Swap - 135i manual trans into a 128i -

[Blau]

Hi all,

I recently picked up a manual transmission from the n54 135i and I plan on tossing it into my 128i, which came as an auto. I want to keep my 128i auto 3.73 diff, so now I have to sort out a drive shaft.

Has this been done before? I can't seem to find any info on how to deal with the drive shaft. Realoem gives me driveshaft lengths, but they're totals, and not broken down by front/rear sections.

Are all the drive shafts the same distance from the trans to the center support bearing? I know the 135i trans is not the same size as the 128i one so I have to account for that as well.

This is all work I can figure out on my own but I'm not trying to reinvent the wheel if I don't have to. Thx

[cerealwars]

I would love to see a breakdown of all the driveshaft and differential combinations available on the 1-series. Maybe there's some info out there that I haven't yet come across.

I really want to put a 3.46 diff into my 128 - sort of a middleground between the auto and the stock manual diff. Maybe one out of a Z4 would fit?

Do you have the 135i driveshaft? You could always have a reputable driveshaft shop splice them together, but I know the measurements need to be pretty precise since BMW didn't use a slip-yoke anywhere. Good luck dude, would love to see how this turns out. Seems we're on a similar path, building fun cars on the cheap.

[Blau]

Originally Posted by cerealwars

I would love to see a breakdown of all the driveshaft and differential combinations available on the 1-series. Maybe there's some info out there that I haven't yet come across.

I really want to put a 3.46 diff into my 128 - sort of a middleground between the auto and the stock manual diff. Maybe one out of a Z4 would fit?

Do you have the 135i driveshaft? You could always have a reputable driveshaft shop splice them together, but I know the measurements need to be pretty precise since BMW didn't use a slip-yoke anywhere. Good luck dude, would love to see how this turns out. Seems we're on a similar path, building fun cars on the cheap.

I don't have the 135i manual driveshaft but will probably pick one up. I was hoping to just modify the 128i auto one, since I already have it and wouldn't need to weld a different flange, but I'd need to weld either drive shaft anyway, so we'll see how it works out.

I'm hoping I like the 3.73 since I bought and refreshed one earlier this summer. I am worried I'll hate it on the highway tho. It's not a daily, so we'll just have to see how it goes.

Peace.

[cerealwars]

Ahh I bet you'll love the 3.73s. I will probably end up going that route, but with it being my daily I'm resisting the urge to go too racecar. The cool thing is I can just swap the stocker back in if I hate it. I feel like worst-case is that you might have to add a resonator back in to manage the drone if you took one out, but the acceleration will going to be too good to turn back.

[Blau]

cerealwars

This is what I found on realoem.

128i Manual - 1439mm
128i Auto - 1353mm

135i Manual - 1371mm
135i Auto - 1373mm

The thing that will help me at this point is figuring out the length of the front section of the driveshaft. I also need to figure out exactly how much longer the 135i manual trans is than the 128i trans.

I love maths.

[cerealwars]

Do you need measurements for the front half of a stock manual 128i driveshaft? I don't want to promise anything, but I will be underneath my car soon for trans and engine mounts. I might be able to snag some measurements if you need. This also might be a good time to check in with a driveshaft shop, as they might be the ones dictating exactly where they need the measurements taken.

[Blau]

Originally Posted by cerealwars

Do you need measurements for the front half of a stock manual 128i driveshaft? I don't want to promise anything, but I will be underneath my car soon for trans and engine mounts. I might be able to snag some measurements if you need. This also might be a good time to check in with a driveshaft shop, as they might be the ones dictating exactly where they need the measurements taken.

I would take any measurements you're offering up.

[Dieselboy]

FYI I documented the swap in my 135i. I was able to keep the auto driveshaft and the auto 3.46 diff with the manual trans. I know it's not the 3.73, but maybe that helps.

https://www.1addicts.com/forums/show...1810392&page=5

[Blau]

Originally Posted by Dieselboy

FYI I documented the swap in my 135i. I was able to keep the auto driveshaft and the auto 3.46 diff with the manual trans. I know it's not the 3.73, but maybe that helps.

https://www.1addicts.com/forums/show...1810392&page=5

Much appreciated. I actually just picked up a used 128i manual trans so I'm going that route. Apparently the 135i manual trans has different gearing than the 128i trans, so the gearing would be weird with that trans and the 128i 3.73. That plus needing a custom driveshaft has me going with the easier swap.

If anyone needs a 135i manual trans... I have one for sale.

[amg6975]

www.driveshaftpro.com will make you any driveshaft you want and are incredibly easy to work with. No one will modify an OEM BMW driveshaft because of the way they're welded.

[dmytro98]

the 135i trans also uses a different input shaft so you would need an n54 clutch as well. You could use a n52 flywheel and pressure plate though.