E46 M3 SMG to Manual Conversion

The E46 M3 had a couple major issues, one of the lesser ones is the SMG gearbox. The hydraulic pump often fails resulting in a costly repair. If this happens to a car you own it often make sense to convert the car to a manual rather than fix the SMG unit. Manual E46 M3’s tend to be more desirable and cost quite a bit more than manual M3’s so often times owners can buy an E46 M3 SMG and have it converted to manual for about the same price as buying a true manual.

SMG to Manual conversion on an E46 M3
The SMG to manual conversion process.

Since the SMG transmission and the 6 speed transmission are internally identical all that is required to physically do this swap is to modify the bellhousing on the SMG transmission. This modification adds in the shift detents so the driver can feel where the gears are. Since the SMG is shifted by the computer these detents were not necessary in the manual gearbox. Machining the bell housing accurately is critical so that the driver can easily find the gears. If the machine work is not precise then the driver can have trouble finding gears as the gates will not be in the correct location. We’ve seen this problem on some swapped cars that have ended up at our shop for troubleshooting.

The hydraulic pump often fails resulting in a costly repair. If this happens to a car you own it often make sense to convert the car to a manual rather than fix the SMG unit.

For race cars it is also possible to swap the 6 speed transmission to a less expensive and rebuildable 5 speed transmission. Coupled with a 3.91 or 4.10 final drive this is often a good race/track setup, but it does require modifying the driveshaft and shift linkage. Overall the cost tends to be about the same as the 6 speed conversion but the 5 speed also has a considerable weight advantage compared to the 6 speed.

This swap also requires the installation of a clutch pedal, master cylinder, and slave cylinder into the car. In addition, the transmission tunnel must be opened up to allow the shifter to be installed. A shifter bushing carrier also has to be installed into the car if a factory style shifter is to be used. Since the transmission will be removed this is also the perfect time to change out that worn out clutch and flywheel.

In order for cruise control, PDC, and the reverse light to function the car must be wired and re-coded as a manual car. The SMG computer is removed and all SMG components are unplugged. The clutch switch and brake switch must be installed and wired appropriately to retain the function of a true manual transmission E46 M3. We also have a special tune for the SMG to Manual conversion, developed by Frank Smith, that adjusts the idle to the correct level and can be coupled with a performance tune upon request.

If you’re considering an SMG to Manual conversion and are near the Orange County, CA area we encourage you to contact us for a quote.

Update: E46 Bellhousing Machine and Prep Service for SMG to Manual Conversion

You asked, we delivered! We practically get daily calls from BMW enthusiasts and BMW shops around the country doing their own SMG to manual conversion. While we love tackling this project for our clients, we know that is not always an option because of time and distance.

We’re now happy to offer an E46 Bellhousing Machine and Prep Service for SMG to Manual Conversions! Just send us your complete bellhousing, and we’ll send it back ready to install into your conversion. Please feel free to reach out if you have any questions – otherwise, check it out on our store page.


  1. Brian C on February 7, 2020 at 12:37 am

    I have a 2004 E46 330i, with an automatic transmission. I also have a 2003 ZHP E46 330i, 6 speed manual transmission, doner car. How many hours of work am I looking at to do the swap? Any ideas.

    • Big Jon on February 13, 2020 at 4:56 pm

      Hey Brian,

      We focus on the M3 for our conversion and it consists of a lot of modifications made along with the Transmission R&R, so I’m not sure exactly what type of time you’ll be looking at for the 330. I waited quite a while to find my 5spd 330i so I didn’t have to find out!

  2. Peter on January 29, 2020 at 2:31 pm

    Hi my shop recently had you all do the machine work on an smg bell housing. Thank you for the excellent workmanship, and quick turn around. The transmission now shifts perfectly, and the car is fun to drive again. Our customer was wanting to get the cruse control working now. could you advise us on how to wire the SMG ecu, and clutch switch to the DME to make this work?

    • Big Jon on January 31, 2020 at 9:26 am

      Hey Peter – thank you so much. It was great working with you, and I’m glad it’s working well. Because there are a few approaches to the wiring and programming, we don’t yet offer remote support for that part of the conversion.

  3. Howard on November 4, 2019 at 3:59 pm

    Can you convert a 2006 SMG E63/650i to Manual? Thanks.

    • Big Jon on November 5, 2019 at 11:34 am

      Hey Howard, thank you for reaching out. While I believe my team could, it’s not a project we currently offer. We only provide this service on the E46 M3s.

  4. Taras M on October 4, 2019 at 1:00 am

    Hey I have a manual transmission that is giving me issues and need a new one. As you may know, manual trannys are pretty expensive. Is it possible to pick up an smg tranny and just swap all the manual stuff except the meat or gears instead of shipping in the smg bell housing to machined?

    • Big Jon on October 8, 2019 at 4:18 pm

      Hey Taras, this is not something we would do and most likely the full SMG transmission is going to be similarly priced. That’s part of why we convert these cars vs. “swap” the transmissions.

      • EC on December 11, 2019 at 10:18 pm

        Used SMG transmissions are less than half the cost of a manual 420g. If you munched a manual it makes total sense to swap your bellhousing onto a donor SMG. You have all the parts and no machine work required.

  5. Franz on May 7, 2019 at 7:52 am

    Also on BMW M3 E36 I can use a bell manual gearbox on the body of SMG and you need any change in that case?

    • Big Jon on May 7, 2019 at 4:37 pm

      Hi Franz, I’m not sure I understand the question. This article is only for the E46 – not the E36.

  6. Miguel Rodriguez on January 10, 2019 at 2:03 am

    I have an SMG transmission in a 330CI 2004, will this fit in my 323CI for a manual shift conversion?

    • Big Jon on February 8, 2019 at 10:32 am

      No, we don’t believe it will.

  7. Andrew Ph on December 18, 2018 at 9:08 am

    Beside modifying the bell housing, I understand that I’d need to modify the gear box for the Gear Identification Switch. What parts will go into the new tapped hole? if you could, please provide the list of parts that I need, part numbers and price.
    Thanks, Andrew

    • Big Jon on February 8, 2019 at 9:44 am

      Andrew – thank you for reaching out. While the information is out there if you do some searching, we don’t provide parts lists/parts kits for the conversion. The only service we offer outside the shop for the conversion is a bellhousing prep service. Anything else (the conversion, programming etc) we only do in house.

  8. Bill on December 14, 2018 at 11:04 am

    Hi there I have a bmw z4 with the ssg is the conversion the same process as the e46?

    • Big Jon on February 8, 2019 at 10:32 am

      No, we don’t know anything about whether this is possible, it’s a different platform and we have not looked into converting it as of now.

      • GrahamK on May 25, 2019 at 6:55 pm


        I have a 2004 330Ci with “SMG” (i.e. SSG) that is 6spd and as far as I can tell the identical Getrag 6MT that is in the M3 (though I could be wrong, RealOEM seems to be confirming this but I’m by no means an expert). Do you know if this conversion process would be essentially identical to the M3, given the same 6MT transmission? I’m getting conflicting answers online in my searches, most seem to be saying “no” (and that a manual swap instead of “SMG” conversion would be the most likely easiest way to go), but others (fewer) are saying it should be similar/identical.

        Any thoughts?


        • Big Jon on June 4, 2019 at 3:29 pm

          Graham, as much as I hate typing this, we don’t know for sure. As we’ve not tackled your exact project, I couldn’t say – wish I could be of more help.

  9. Spencer ives on November 12, 2018 at 9:35 am

    When sending back bell housing. What’s the wait time and shipping method. Do I ship it out of pocket? Or when I purchase this does it send me a rma?

    • Big Jon on November 16, 2018 at 10:39 am

      Hey Spencer, thank you for asking and I’d like to clarify how to get your bellhousing to us and back.

      – First you’ll want to order the service here – this will calculate and charge you for the service and return shipping only.
      – Then you’ll need to prep and pack your bellhousing. It is a good idea to print a copy of your order confirmation and throw it in the box if possible.
      – You will need to arrange and pay for shipping the bellhousing to us.
      – Once received, depending on the queue, it takes about 3 days to complete.
      – Return shipping speed will be based on the options you select at checkout.

  10. Zoltan Merkovic on September 10, 2018 at 7:45 am

    Can I use a manual bellhousing on smg body and is it required any modification in that case?

    • Big Jon on September 12, 2018 at 11:44 am

      Hey Zoltan, Yes you can… If you can find a manual bellhousing 🙂

  11. Paul on December 8, 2017 at 6:07 am

    Why are the 6 speeds not rebuildable?

    • Andrew on January 12, 2018 at 7:24 pm

      Paul – the simple answer is that BMW doesn’t sell the parts required for that job.

  12. Edward RobinsonNorris on October 26, 2017 at 3:08 pm

    I have a spare SMG bellhousing, is it possible for you guys to machine it to spec.

    • Andrew on November 1, 2017 at 5:22 pm

      Hi Edward,

      We have started prepping bellhousings for people, I would need some more detail – Jonathan will email you to get some info and we’ll go from there. Thank You.

  13. Ervin Arnaszus on August 11, 2017 at 9:23 pm


    Would you be able to remotely code out the SMG out of an m3?
    I have access to Autologic and BMW Ista

    • Andrew on September 4, 2017 at 4:43 pm

      Unfortunately this is a service we only provide in house.

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