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6-Speed Transmission Pros/Cons?

Discussion in 'E36 M3 (1995-1999)' started by mtrevor, May 4, 2010.

    mtrevor guest

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    I recently purchased a modded '98 M3 Sedan. The car is pretty quick as it has quite a bit of power-adding upgrades. I was wondering if there is a bolt-on 6 speed transmission for my car. The revs are quite high at highway speeds with the 5-speed and it is has plenty of torque for low RPM passing, only thing is, it gets up there so fast and run out of gear. Speeds approach mid triple digits quickly.

    Reasons for extra cog:

    1) Lower cruising RPM
    2) Higher top speed

    Concerns in switching:

    1) Durability
    2) Fitment
    3) Cost-prohibitive
    4) Potentially shorter lower gears (ex: When I turbocharged my '00 Miata, I had the factory 5-speed. I was planning on upgrading to the factory 6-speed only to find out that the first 5 gears in the 6-speed were equivalent to the first 4 in the 5-speed, rendering the swap useless has I gone through with it)

    Any input or guidance on this would be greatly appreciated.
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    bcweir

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    If you do decide to do this upgrade, I found something for you

    Zionsville Autosport sells two versions of the upgrade kit: one version is without the transmission (you source this yourself), and another version includes the transmission (this is likely to be a lot more expensive, but will save you the possible aggravation and grief of picking up a used one and discovering it to be a abused one instead). If you can source a six speed manual compatible with your engine on your own, that wasn't thrashed within an inch of its life by Ronnie Ramjet or Johnny Hardcoreracer, go for it. At $4,993.86 for the kit WITH the transmission, Zionsville Autosport's tranny-included package ain't cheap. But in their defense, paying too much for an abused tranny off Ebay or Craigslist isn't wallet friendly either.

    If you want to source yours yourself, Zionsville claims their transmission is a ZF model GS6-37BZ found in the new E46/E9x 330i/330Ci, E85 Z4, and the new 5-series (presumably an E60 or an F10). If you can find one that was wrecked and not raced, abused, or neglected, you might get lucky as long as its not damaged and you don't get raped on the price. You may also be able to google this transmission model and find a direct vendor. You might also want to ask how much power this transmission is rated to handle. Non-M cars didn't have a whole lot of power behind this six speed, and I don't know what your power output is on your modified M3, but it's likely a lot more than the 200 to 225hp these non-M baby sixes are rated at. You might also get lucky with a 1-series car also.

    http://www.zionsvilleautosport.com/store/screen/prod/store_code/6134/product_code/6SP000-1.htm

    If you don't mind me chiming in with a personal opinion, I'd like to point out that whether or not this is worth the expense depends on whether you're trying to get more versatility out of your current car, or if you're doing it to get an extra few MPG. If you're doing it strictly for extra MPG, the numbers are not going to work for you. Spending five grand or more to get an extra one to three MPG difference is going to take you YEARS for the gas savings to pay for itself, and each time you mash the throttle (the temptation is HUGE on a modded M3), you'll be setting yourself back from your "break-even point"). By that time, you will have likely gone through at least one or two more clutches, setting yourself back again. M3's are not known for their "legendary" gas mileage, six speed conversions aside. That's what BMW made the E36 318ti for. You could buy an extremely nice and fuel friendly E30 or E36 318 for the amount of money this conversion will likely cost you when all is said and done.

    But if you're doing it to try and get some more versatility out of your car, with a few MPG savings as a fringe benefit, AND if you don't mind tackling the expense and labor of doing this, I'd say go for it.

    At any rate, I don't want to discourage you. I just want to make sure you have realistic expectations about what this conversion can and cannot do for you. If you decide to go for it, please keep us posted on what happens.
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    tiFreak

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    the euro-spec M3s came with a 6-speed, it would be hard to find one but it would be built to withstand the power from the M engine
    • Member

    bcweir

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    The problem with shipping a Euro E36 6-speed: got $7,000?

    That figure doesn't include shipping across the Big Pond, and it's a pretty heavy and expensive item to ship.

    On the other hand, this webpage says that a 6-speed from the E46 M3 is a direct bolt in. However again, it's not cheap.

    http://www.uucmotorwerks.com/98M3/upgrades/E46M3_6SPD/index.htm
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    az3579

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    A 6-speed for his car is NOT that much money, Brian. Anyone who buys an engine or transmission from Zionsville has got to be off their rocker. You know how much they wanted for their M50 swap kit for my car? A Helluva lot more than what I spent total for my S50 swap.


    I'd get a used transmission from a junkyard or something, with a warranty. Some of the places offer a limited warranty on it, a short amount of time yes, but once installed you can easily check for problems. Yes, it's more of a hassle, but the chances of finding a good one are high.

    Or, look for a "parting out" thread on one of the forums, and look for an E46 or something. I might plan to do this down the road.
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    bcweir

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    In that case, he could just as easily source his own transmission...

    ...and just buy the conversion kit.

    As far as WHICH transmission he gets, I believe the transmissions for the M-engines and S-engines are different internally, with the S-engine versions likely having beefier components. Otherwise, my understanding is that they interchange with the M-code/S-code engines. He could probably further reduce his cost by purchasing an M-grade transmission, but there's no telling how long it could live behind his modified M3 engine, considering he didn't mention how much power it was making. That's not something I'd want to place a bet on with a six speed manual made for a M-engine making only 200 to 225 hp, considering that even a stock S50/S52 was making 240 in US trim.
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    Wretched

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    Might be much cheaper to change the differential gearing instead. it wont be as dramatic but can drop some RPM's raise over all speed slow acceleration a tad. If it has mods and your not running it 1/4 mile this might be a cheaper alternative.
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    az3579

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    Brian,
    BMW doesn't put transmission in its cars that cut the limits short. That example you used of using a 6-speed designed for a 200-225hp car in a 240hp car isn't a good example, because that would be a stupid move on BMW's part to put a transmission that's that close to its limit. BMW knows that people will modify their cars down the line, probably one reason they have a margin of error on speedometer ratings to take into account the probably someone will put different wheels/tires on the car at some point.

    That, and not all trannies are different between M and S models. My transmission, a ZF S5D320-Z, came from a 328i, not an M3. But, the M3 and 328i used the same transmission, despite the M3 packing much more power. The 6-speed box from a 330i should have no problem handling an S50/52.




    Not quite a solution. I have the same transmission as the OP, and I have a 2.93 LSD in my car, which is taller gearing than the OP, and I get ridiculous RPM's on the highway as well; just below 70 yields 3000rpm. I'm not sure if there any taller diffs he can fit in his car anyway...
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    Zeichen311

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    For the record, the more important figure for matching a transmission to an engine is torque, not horsepower. Excessive torque is what removes important bits of the gearbox from their assigned places and piles them up in the bottom of the case.

    Example: An engine that makes 200hp at 5000rpm generates about 210 lb-ft torque at that angular speed (HP and torque are mathematically related). An engine that makes 200hp at half the speed (2500rpm) is applying twice the twist to do it: 420 lb-ft.

    Transmissions mated to these hypothetical engines would both be handling 200hp. Assuming each was "just strong enough," guess which one would fail if you could swap them. :D
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    bcweir

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    I didn't say anything about BMW doing that

    I never said that they did. What I am saying is that BMW obviously has to build a stronger transmission to withstand 400 hp than one that only needs to withstand 225 to 240. If he's modified an E36 M3, he's certainly making more than the stock US 240 hp.

    By the way, nearly all modern BMWs since the mid-80's derive their speed signal from a speed sensor mounted in the differential. This speed sensor is geared to the final drive ratio and derives the proper speed signal based on the rotation of the signal it receives from this sensor. As long as your overall wheel and tire size diameter is roughly close to stock, your speedometer calibration should remain relatively close to stock.

    mtrevor guest

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    Thank you for all of your responses. I am going to look at all my options. I will check out all the suppliers that carry a conversion kit and used tranmissions as well as salvage yards with a warranty and those who may be parting out their cars.

    I would like to compare the gear ratios from the transmissions as well. My main goal is to have slightly longer gears plus a tall over drive for lower cruising RPMs on the highway. After talking with some BMW peroformance guys, I should have approximately 315 crank HP, or somewhere around that number. I am not sure what my torque figure is, but I'm sure it is somewhere around 280 at the crank.

    MPGs are not my main goal, but a lower highway cruising RPM would most-definitely increase my fuel economy. In the end, I know I won't make my money back on fuel economy, but it will be nice to have to fill up less, during those times I'm not mashing the throttle ofcourse.
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    bcweir

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    This is what I found

    If you're doing 315, you definitely want to make sure you get the S54 transmission. There are TWO of these. The S6GS 420G went into the E46 M3, 2000 model year and later. That BMW part number is 23002229721, and it retails for $6,345.16 (I'm sure you can do better than that though, pricewise). It should be noted that the version that went into the Z4 M Roadster and M-Coupe is a different six speed, although those two cars shared the same S54 engine. The reasoning for this is that BMW claimed that the E46 transmission wouldn't fit in the Z4 body. The Z4 M transmission, model number GS6-37BZ/DZ, part number is 23007837983) $3,801.30+core. (I don't know what the core charge is, you may have to contact the dealer). Either one should fit in your E36. My estimation is that the Z4 part simply has a different casing to suit the Z4's somewhat tighter accommodations. The internal guts are likely similar if not identical.

    Just for laughs and giggles, I checked on the E46 330Ci as well as the E9x 330 also.

    For the E46 330Ci, it shows TWO versions of this transmission. The GS6-37BZ-TBEZ (part number 23007562725) was for cars up to 3/2003 production dates. This was replaced by GS6-37BZ-THEG (part number 23007532498) $3,801.30 +core. What's interesting here is that although the part numbers and model numbers are different from the Z4 M 6-speed, the prices are identical to the penny! For this reason, I believe that the 330 6-speed and the transmissions for the E46 M3 and Z4 M cars are indeed apparently different.

    For the E9x 330i, realoem shows yet ANOTHER model number and part number, again the prices are identical to the Z4 M part and the E46 330Ci 6-speed. GS6-37BZ - TJEP through 03/2007 (BMW part number 23007565853) $3,801.30

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