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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.

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Old Wed, May-15-2013, 01:13:06 AM   #1
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Default Comprehensive SMG to 6MT Conversion Thread

Before I begin, I would like to thank everyone on the forum who has performed this swap before me. In particular, thank you to wrxnoob (the original!), RAZ M3, Performance Technic, M3SMITHNWESSEN, and especially beomoua, see.m3.go, and Abad46 for answering my specific questions and making themselves available to me whenever needed! I would also like to thank the few people who's pictures I have "borrowed" for the steps at which I was either too frustrated or too short on extra hands to take pictures

So, how difficult is this to take on by yourself on jackstands? Well, looking back at it now that it’s done, it is hard to claim that it is all that much more challenging than doing a clutch replacement. Sure, there are a few extra steps- however, if you are capable of doing everything that leads up to the point where the projects differ, then you are capable of getting through the whole thing.

The Parts List:

There is a fair amount of hardware included in the list that will not absolutely be needed, but is nice to have in case of damage to existing hardware during the disassembly process. There are kits available, but I chose to source the parts myself. Doing so built confidence, as I became very familiar with the OEM parts diagrams and how everything is intended to fit together. Again, sourcing the parts yourself will allow you to truly tailor your job and guarantee that you can replace anything you deem necessary, rather than the bare minimum to get it done.

It is common knowledge that one of the physical differences between the SMG and manual transmissions is the bellhousing. Specifically, the SMG bellhousing is missing the spring and detents that give the self centering function to the manual version. Although it can take quite a long time, I would recommend making an effort to find a factory manual transmission bellhousing. It not only allows you to immediately make the swap when you get to that point, but also guarantees OEM functionality and eliminates the possibility of human error during modification of the SMG BH at a machine shop. If you can find one, it will also probably save a fair amount of money versus paying a shop to modify yours.

Bellhousing and Transmission Parts       
List #PartSourceSource P/NBMW P/NQTYPriceExt. Price
16MT Transmission BellhousingForumsNANA1$200.00$200.00
2Locking PinGetBMWParts 231112229791$12.88$12.88
3Compression SpringGetBMWParts 233112283931$4.32$4.32
4Sealing CoverGetBMWParts 231275274392$4.59$9.18
5Lock RingGetBMWParts #071199346242$1.69$3.38
6Locking PinGetBMWParts 233112241301$11.10$11.10
7Compression SpringGetBMWParts 231112227201$8.99$8.99
8Torx Screw, micro-encapsulated M8x25GetBMWParts 233175866371$2.57$2.57
9Comrpession SpringGetBMWParts 233175113371$5.88$5.88
10Compression SpringGetBMWParts 233112284051$5.75$5.75
11Gear Identification SwitchGetBMWParts 231422291131$78.02$78.02
12Cable ClampGetBMWParts 117875472131$0.30$0.30
13Cable ClipGetBMWParts 345211646531$0.30$0.30
14Pentosin MTF2 (OEM Fluid)ECS Tuning *832203090312$22.50$45.00
15Locking PinGetBMWParts 233175015841$20.83$20.83
16Thrust PinGetBMWParts 233112824441$11.49$11.49
     Trans. Parts Total: $419.99

Optional Short Shifter Parts      
List #PartSourceSource P/NBMW P/NQTYPriceExt. Price
1Shift KnobECS TUNINGES#:47396251178968841$60.55$60.55
2Shift Boot AlcantaraECS TUNINGES#47399251179192191$55.00$55.00
3BMW Performance Shift LeverECS TUNINGES#:1895170251175272591$66.44$66.44
4Shifter Ball BushingECS TUNINGES#:2574768251114693971$8.00$8.00
5CirclipECS TUNINGES#:254614251175718991$1.00$1.00
***ECS KitECS TUNINGES#46511NAShifter Parts Total: $180.80

Remaining Gearshift Parts (minus shift rod, ball bushing, shift knob, shift boot)      
List #PartSourceSource P/NBMW P/NQTYPriceExt. Price
1Shifting ArmGetBMWParts 251122287101$23.39$23.39
2Bush Bearing OvalGetBMWParts 251175076951$3.54$3.54
3Bearing BoltGetBMWParts 251175290791$4.24$4.24
4Bearing Shifting ArmGetBMWParts 251112220151$18.86$18.86
5Shifting Arm Bearing BracketGetBMWParts 411282462511$21.43$21.43
6Rubber BootGetBMWParts 251175221491$13.37$13.37
7Selector RodGetBMWParts 251122287111$40.30$40.30
8Plastic WasherGetBMWParts 251112204398$0.48$3.84
9Securing Clip (Shift Lever AND Selector)GetBMWParts 251175718994$0.84$3.36
10Gearshift Rod JointGetBMWParts 251112226881$16.35$16.35
11Lock RingGetBMWParts 251112224511$0.62$0.62
12Plastic Washer Type 2GetBMWParts 251114341941$2.06$2.06
13Dowel PinGetBMWParts 234114661341$1.08$1.08
14Insert Shifter CoveringECS TUNING 251114341001$16.82$16.82
     Gearshift Parts Total: $169.26

Clutch Assembly (Pedals, Clutch Control Parts and Hydraulics, Electrical)      
List #PartSourceSource P/NBMW P/NQTYPriceExt. Price
1CirclipGetBMWParts #071299045673$0.28$0.84
2Bush BearingGetBMWParts 352111582902$1.50$3.00
3Return SpringGetBMWParts 353011653211$1.43$1.43
4GrommetGetBMWParts 354111137283$1.37$4.11
5Module, Clutch SwitchGetBMWParts 613191227001$48.86$48.86
6Clutch PedalGetBMWParts 353111638701$30.98$30.98
7Pin, Master CyclinderGetBMWParts 353168542831$2.96$2.96
8Rubber Pad, ClutchGetBMWParts 352111086341$3.58$3.58
9Clutch Pedal Stop BufferGetBMWParts 353167505691$0.88$0.88
10CLUTCH STOP- ClipGetBMWParts 514882458671$0.49$0.49
11CLUTCH STOPGetBMWParts  1 $0.00
12Input Cylinder Clutch (Master Cylinder)GetBMWParts 215267736701$122.70$122.70
13Hex BoltGetBMWParts #071199029971$0.77$0.77
14Hex BoltGetBMWParts #071199029761$0.58$0.58
15Hex NutGetBMWParts #071299048761$0.43$0.43
16Repair Kit Clutch Plug-in ConnectorGetBMWParts 215211654511$7.08$7.08
17GrommetGetBMWParts 215268630431 $0.00
18HoseGetBMWParts 215211637141$7.70$7.70
19PipeGetBMWParts 215267742741$42.90$42.90
20Pressure Hose AssemblyGetBMWParts 215267742671$24.18$24.18
21Support Pressure Hose AssemblyGetBMWParts 215222296991$1.90$1.90
22ClipGetBMWParts 343411635651$0.78$0.78
23PipeGetBMWParts 215222296751$27.28$27.28
24Vent ScrewGetBMWParts 215211163601$6.88$6.88
25Dust CapGetBMWParts 341111531981$5.42$5.42
26Output Cylinder, Clutch (Slave Cylinder)GetBMWParts 215267859661$63.63$63.63
27Knurled BoltGetBMWParts 215112030122$1.62$3.24
28Self Locking Hex NutGetBMWParts #071299061962$1.34$2.68
29GrommetGetBMWParts 215211638941$2.92$2.92
30Pipe ClipGetBMWParts 161211767671$1.44$1.44
31Clutch Switch Adapter LeadGetBMWParts 611169110721$7.90$7.90
     Clutch Control Total: $427.54

Other Replacement Parts      
List #PartSourceSource P/NBMW P/NQTYPriceExt. Price
1Hose Clamp (Intake Manifold)GetBMWParts 116178317456$2.74$16.44
2Ball PinGetBMWParts 215112233281$1.52$1.52
3Spring ClipGetBMWParts 215175702841$4.82$4.82
4Guibo Nuts (One time use)GetBMWParts #0712990004712$1.03$12.36
     Other Parts Total: $35.14


Recommended Tools:

-M14x1.5 thread tap for the gear recognition switch. If you’re having a machine shop modify your bellhousing, perhaps it would be easier to have them tap this hole in the gearbox as well.
-Array of 3/8” drive extensions. You will need between 3 and 4 feet in order to reach some of the top bolts on the transmission bellhousing.
-Several universal joints. I would suggest impact rated joints, as I managed to grenade several non-impact joints trying to break bellhousing bolts loose.
-Female torx sockets.
-Lisle earless CV boot pliers for intake manifold clamps.
-Impact wrench.
-Transmission jack. Again, trannys have been dropped using a standard hydraulic jack… This job is involved enough that it is well worth the $70 for a solid low profile transmission jack. Harbor freight makes an excellent product for this.
-Oil resistant black RTV for sealing the new bellhousing to the transmission.
-White lithium grease (no, not the spray on kind) for the throwout bearing guide tube and contact points on the clutch fork.
-Either a welder or ¼” rivets and a riveting gun.

OEM Parts Diagrams:

Do yourself a favor, and study these parts diagrams! It will also be very helpful to have a printed version of each of these on hand for both assembly and disassembly. Again, it was massively helpful for me to “build” my own parts list by working my way through these exploded diagrams! The original version of these is available on

Procedure (Mechanical):

1. Open the fuse box in the driver’s side corner of the engine bay, and remove the SMG salmon relay. Make sure the transmission is in neutral! Disconnect the battery from the car.

2. Remove the intake manifold. There are several DIY’s available for this. Personally, I chose to use the highly detailed starter motor replacement DIY seen in the link below. Using the Lisle earless CV clamp pliers will save a huge amount of time and effort here. Once the manifold is out, open the SMG fluid reservoir and empty it into an oil drain pan or equivalent.

With the intake manifold removed, the SMG pump will be exposed. I chose to leave the pump connected for now to hold the hydraulic lines out of the way, and to allow the system time to depressurize as I continued to work on the other aspects of the conversion. It is suggested that you cover your intake throttle bodies with painters tape to prevent random debris from falling inside. For reference, this picture does a good job showing the full mechanical layout of the SMG system.

3. Put the car up on jack stands at all four corners. There are plenty of write-ups on how to do this, but just as a quick reminder: DO NOT support the rear of the car by the factory jack pad points. They will bend. Instead, use the spots just to the inside of the jack pads where the “V-shaped” chassis brace bolts in. Also remember to lift the rear of the car by the subframe, NOT by the differential! The front jack pads are fine to support the car by. My only other suggestion in lifting the car is to get it as high as safely possible. You will be eternally grateful for every bit of space available to you.

4. Remove the skid plate (17mm hex bolts), and all of the plastic splash guards you can get out of the way (combination of 10mm and 8mm hex bolts, and plastic rivets).

5. Remove the entire exhaust by disconnecting first at the flange where the headers mate with section 1, and then by removing the 4 copper nuts that secure the muffler to the rubber mounts under the rear bumper. Keep in mind that you will also have to remove the two rectangular exhaust braces, and the one V-shaped chassis brace. Your impact wrench will save you a huge amount of time. Use a jack to support under the muffler, and slowly lower / manipulate it so as not to put any weight on the rear bumper diffuser. It will help to keep the front of the exhaust (at the headers) supported by a jackstand so that it does not drop.

6. Remove the metallic exhaust heat shields to expose the drive shaft.

7. Support the transmission behind the drain bolt, and remove the transmission support brace.

8. Mark the outline of the center support bearing mounting flange using a sharpie. The bearing is preloaded and will need to be mounted in the exact same place during reassembly to prevent premature bearing wear.

Use a 13mm socket to unbolt the center support bearing. Using an 18mm wrench and an 18mm socket, disconnect the six nuts and bolts from the guibo. Lower the driveshaft, and support it behind the universal joint with a jackstand or tie it up and out of the way with some string. Do not allow the driveshaft to hang by the CV joint at the interface with the differential. There is no need to separate the driveshaft at the universal joint or to unbolt it from the differential for this job.

9. Remove 17mm drain plug to drain transmission fluid (replace plug once empty to prevent contamination), unplug all electrical connectors, and remove the SMG hydraulic lines from their clips. Unplug each of the electrical connectors going to the transmission. Unbolt the SMG slave cylinder from the transmission with a 13mm socket on an extension.

10. Disconnect the 4 hydraulic lines from the SMG pump from inside the engine bay. I was lucky and these came off with very minimal effort, though some for some people they can be seized on pretty tightly. If they are stuck, it is not a problem. The transmission can be lowered with the pump still attached, enough to remove the hydraulic lines at the shift actuator and slave cylinder. Either way, the SMG pump will be removed from the top, and now is a good time to do that. For more information on removing the SMG pump, refer to the following link:

11. Place a jack under the front of the engine (in front of the sway bar) and raise it high enough to support and prevent the motor from tipping forward once the weight of the transmission is removed from it. It is easy to see that it will rock forward and crack your fan due to the rearward location of the motor mounts.

12. Now it is time to drop the transmission. Keep in mind that it IS POSSIBLE TO DROP THE TRANSMISSION WITH THE SHIFT ACTUATOR STILL INSTALLED ON THE CAR. Do not bother wasting your time removing circlips and pressing out pins with everything still mounted up. Refer to the diagram below for the location of each of the bellhousing bolts. There are three different size bolts (M8, M10, and M12) each with a different size external torx head. USE A SHARPIE TO LABEL THE HEAD OF EACH BOLT WITH THE CORRECT NUMBER AS YOU REMOVE THEM! Also note that during reinstallation, each size screw will have a unique torque spec.

This is where the female torx sockets will be used. In order to reach the bolts on top, I taped together between three and four feet of extensions with a universal joint on the end and snaked them through over the top of the transmission. This will require some serious patience, and a helper who can guide the socket onto the head of the bolt from the engine bay will be of huge help. Once the socket and extensions are in place, go to town with your impact wrench and/or breaker bar. You will likely have to adjust the angle of the transmission and engine by lowering and raising your transmission jack depending on which BH bolt you are trying to remove. After all of the bolts were removed, I had a very difficult time pulling the starter motor off because of the alignment pin that extends from the BH into the starter flange. Be patient wedging a flat blade screwdriver or similar in there, and let some PB blaster soak into the joint to help break it loose.

Once the starter motor is removed, pry the transmission away from the block being extremely careful not to let the input shaft hold the weight of the transmission while lowering it (make sure to pull it beyond the clutch spline!). Once the transmission was away and lowered, I had to lift it off of the tranny jack and onto a piece of cardboard to slide out from under the car.

13. Remove the SMG shift actuator from the car. There will be three bolts that the arms hard mount to. To remove the actuator the rest of the way, use a flat blade screwdriver to push the circlip on the shift rod joint out of the way, and use a thin punch to knock the pin out of the joint. Remove and inspect your throwout bearing, clutch fork, and throwout bearing guide tube.

14. Remove the bolts holding the BH to the gearbox using a 13mm wrench. Once all of these are removed, lightly tap on the bellhousing with a rubber mallet until it separates from the gearbox. Do not attempt to pry the faces apart, as these faces need to maintain a good seal when reassembled. If you gouge them, you will leak transmission fluid. Pull the BH the rest of the way off, being very careful not to pull off any loose transmission components with it (several small bearings/washers can fall off the end of one of the shifter rods). The following is a picture taken by Performance Technic, which shows the washers and pins that they ride on, which you’ll want to make sure are firmly in place before continuing. You’ll also want to be careful not to damage the input shaft seal if you are not replacing it at this time.

15. Making sure that all of the inner gearbox pieces are where they should be, install your new manual bellhousing on the SMG transmission. Remember to apply a bead of black RTV sealant all the way around the face of the flange and each bolt hole. The RTV should “dry” within an hour, and be fully cured within 24 hours. To be safe, I did not fill the transmission with new fluid until after the 24 hour period.

16. Remove the pressed in plug on the back of the transmission- this is where the gear recognition sensor will be installed. I was able to do this by lightly prying on it with a flat head screwdriver- it should not put up much of a fight. Be c[areful not to damage the inner diameter of the hole. Also remove the bushing and compression spring. My compression spring, as seen in the picture, was cracked!

It must have only been a matter of time before the transmission was no longer capable of shifting or staying in gear. This is a perfect example of why you should go ahead and replace all of the compression springs while the transmission is off of the car. Use the M14x1.5 tap to thread the hole (the pre-drill diameter is already correct for use with this tap). I used a heavy grease on the tap in order to collect chips as I went. Besides for following the conservative “one turn in, half turn back” pattern for cutting the threads, after every two full revolutions I backed the tap completely out to clean any chips that may have not stuck in the grease with a cue tip. The key here is to TAKE YOUR TIME. The last thing you want to do is to have to fish out small metal chips from the back of the gearbox.

Once the threads are cut as deep as they will go (the tap will stop when the end contacts the pressed bushing inside), clean out any excess grease and install your new shift detent, spring guide pin, and compression spring. Yes, these parts are different between the SMG and manual cars- do not try to reuse those from the SMG. Finally, screw in your new gear recognition sensor. Once the transmission is installed in the car, a now unused SMG connector will hook up to this sensor. In order to mate these connectors, the center plastic tab on the outside of the gear recognition sensor will need to be sliced off with a razor. Again, looking at the connectors side by side, it will be very obvious what needs to be cut off in order for them to work together.

17. Reinstall your throwout bearing guide tube (lubricate with white lithium grease), clutch fork (lubricate contact areas on back side with white lithium grease), and throwout bearing.

Then go ahead and install your slave cylinder, bracket, and the soft hydraulic lines that attach to it. No need to overtighten these fittings!

18. Get inside the car and remove the SMG shift knob (just pull straight up). Next remove the SMG shifter bezel (which simply pops out of its clips). Now that the shifter module is exposed, remove the three 10mm nuts, unplug all of the connectors, and pull the shifter off of the three studs it rides on. You can now see the top of the blockoff plate that is spot-welded underneath the car. Here is a picture borrowed from another forum member who has done the swap:

19. Now it is time to grind off the blockoff plate that the new shift lever will go through to mate with the selector rod. This was by far the dirtiest and most tedious part of the job. I used an assortment of grinders, drills, etc. to try and cut through the spot welds on the plate and remove it. What ended up working best, once I had removed the rubberized undercoating, was a Kevlar cutting wheel on my dremel due to its precision. Again, take your time and let the tools do the work- you will get through it. You may also want to tap down on the plate from the top with a wood block and mallet in order to more clearly define the edge of the plate from underneath. This will make sense when you see it. Here is another reference picture taken from Performance Technic to show where the spot welds under the plate are located. This picture also clearly depicts the proper orientation of the shift arm support bracket:

Last edited by Obioban; Fri, Jul-21-2017 at 11:05:06 AM.
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Discussing Comprehensive SMG to 6MT Conversion Thread in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)