Tech Write-Up: BMW E46 M3 SMG to 6spd Manual Conversion


BMW’s E46 M3 is arguably the best ///M car to date.

A high revving straight six with beautifully tuned individual throttle bodies, boasts an impressive 333hp, with nimble handling, an aggressive stance and body design that still competes with today’s exotic cars. Unfortunately and at many owners expense, it had one major downfall;

The SMG transmission


Although the technology of the SMG (Sequential Manual Gearbox) was really cool and had “lightning-fast” shifting, (.65 milliseconds to be exact, which was second only to the Ferrari), It was plagued with expensive issues and a sloppy performance in comparison to today’s newer technology, namely BMW’s new DCT (dual-clutch transmission).

The SMG transmission was promoted as newer, cutting-edge technology. Now that many SMG equipped vehicles have aged with higher mileage, current owners are faced with very expensive repairs when anything fails.

EuroMpire Has the SOLUTION.

Give control back to the driver!  We have extensive experience swapping the SMG transmission to its highly desired, 6 speed counterpart. The best news is, we can use the transmission that’s already in the car, eliminating the cost of buying a new or used transmission!  When BMW built the SMG transmission option, they basically bolted on several electronically controlled hydraulics. To prevent overworking or premature failure of the hydraulic components, BMW removed a few internal shifting parts of the transmission.

Once the driver decides they have had enough of the SMG transmission (usually when the hydraulic pump fails and they are facing a $3k plus repair) they drop the car off for the swap!

Our Repair Process

We begin by removing the transmission, driveshaft, the old hydraulics, the old shifter, and paddles, including all wiring that will no longer be used.

We box up the old parts and give them back to the customer. Many customers have sold the old parts online or have taken them into a field and handled them like the printer on the movie, ‘Office Space’. (Don’t forget your baseball bat.)

Parts for BMW M3 SMG to 6spd conversion

Next, we install the new parts needed for the manual transmission. We have to cut out the plate that blocks the shift lever hole and weld in the bracket that holds the rear shift lever bushing.

 

bmw smg to manual six speed bmw clutch pedal

Secondly, we install the clutch pedal, shift lever and return springs. Note: we can install the shift boot and shift knob as chosen by the owner. Next, the clutch pedal switch is wired in. We find the factory knock outs for the clutch hydraulic lines and run the lines to and from the new master cylinder.

Now.. the COOL part of the process..

We set the transmission up on the bench and remove the bellhousing portion. Then, we disassemble the shift rod holder and clean the housing.

We cover the bearing and then drill two holes for the new shift detents. We press a small bearing onto the shift rod holder for the new detents to ride on. Next install a return spring to center the assembly when the shifter is put into neutral. We have to machine two grooves for the snap rings. Then drill one last hole for the spring to rest on and install a specially machined pin.

Now that that’s done, we clean the bellhousing, thoroughly grease the new components and reassemble everything. We take special care to be sure everything is properly lined up and sealed!

With the transmission reassembled, we have to thread the hole at the back of the transmission that holds the new gear recognition switch. This new switch also uses a different detent, spring and pin. That finalizes the transmission work!

Before we reinstall the transmission, we must remove the clutch and determine whether it needs replacement, or just to be reset.

Assembly from this point is the same as installing the regular 6 speed transmission. We install a new slave cylinder and line, then hook up the new shifter. We reassemble the drive-line exhaust, heat shields and the rest of the under-body.

 

Although this swap can be difficult for some, we usually complete the job between 5-7 days at a cost starting at $3500.00

The swap requires some wiring. The wiring isn’t very straight forward. Different model years with different options require different wiring strategies. Simply comparing wiring diagrams between SMG and 6 speed models lets us know what to do!

The same goes for coding. Different years have different requirements, although we know we will always need to re-code the DME (digital motor electronics) and instrument cluster.

During the entire process, we check any related components for failure or wear, such as the transmission mounts or the Guibo.

When the swap is complete, the drivers, passengers and any other onlookers will have no idea the car was ever equipped with the dreaded SMG transmission.

We welcome any questions. Feel free to call or text us anytime! 704-777-0006 or email to talk about your options, or set up an appointment!