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E46 M3 SMG to Manual Conversion

SMG to Manual conversion on an E46 M3

The SMG to manual conversion process.

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.

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. 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.

  2. 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 🙂

  3. 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.

  4. 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.

  5. 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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