12-29-2018, 11:00 PM | #1 |
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S55 6spd Transmission Swap
I'm wondering if anyone has gone down or explored this path?
Some background, my car is need of a new clutch/flywheel (clutch is slipping due to tune and my flywheel recently started rattling). Started doing some research and it seems as though the S55 6spd clutch and flywheel can easily handle 600wtq with no issues and still has oem driveability. Using this flywheel requires the use of the S55 6spd trans due to the output shaft length required for the clutch/flywheel combo. Started looking around and found a local dismantler parting an F80 m3 with 3000miles and offered me the trans at a ridiculous price, so this really got the wheels turning for me. I've done some research on real OEM and google and it seems as though the clutch/flywheel/trans "should" bolt up to the n55. My concern is the overall length of the transmission? Anyone know if the dimensions are the same as F30 6spd trans? Or have a method to measure or share some overall dimensions for either trans? I'm concerned about the driveshaft length and it doesn't seem like the F80 driveshaft can work in the f30 without swapping the diff? Also are output flanges the same or can they be swapped? I'm sure the the first comment is going to be "just go aftermarket clutch and SMF" but that is not an option for me. I have no interest in having any of the rattle associated with the SMF and would rather spend more on a solid OEM set up. My ultimate goal is 500wtq to redline with a larger turbo set up (top mount or bottom mount kit) which I believe this clutch/flywheel combination should easily handle. Open to any input, I hope I don't end up being the guinea pig for this...lol |
12-30-2018, 05:09 AM | #3 |
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This is the smartest thing to do 1000%
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09-26-2021, 06:38 AM | #4 | |
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I'm looking to swap an M4 6MT into an N55 435i so I can go with a big single turbo. The stock 6MT the F32 came with probably wouldn't live well in that world. |
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09-26-2021, 11:03 PM | #5 |
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09-27-2021, 06:17 PM | #6 | |
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Big power = no transmission. Seems like the S55 M4s are getting into the +900whp range with upgraded clutches, so that transmission must have better power handling capabilities. Plus, it must be dimensionally close to what the N55 6MT is as the F82 is essentially a nicer version of the F32 body. |
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09-27-2021, 06:22 PM | #7 | |
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Also curious to know how the S55 transmission "must have" better power handling capabilities as compared to the N55 one, aside from anecdotal evidence based on S55 cars making more power? Is there documentation on the transmission internals? |
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09-27-2021, 06:41 PM | #8 | |
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I get the synchro is the failure mode, trust me, but that's still an internal transmission component failing and rendering the transmission useless. You seem to categorize this differently for some reason (?), as if a gear or shaft are the only items that can fail and "rightfully" qualify as a transmission failure? I'm not certain what value splitting those particular hairs is creating? As far as the power handling capabilities of the S55 6MT, that's simply empirical data. If you're looking for me to qualify that for you, I'd suggest this isn't the thread for that. |
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09-27-2021, 08:36 PM | #9 | |
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Also, you opened with: "I'm looking to swap an M4 6MT into an N55 435i so I can go with a big single turbo. The stock 6MT the F32 came with probably wouldn't live well in that world." So once again, the syncro concerns have nothing to do with going big single turbo. You then reiterated the focus on "big power" in your subsequent posts. So my point is that I have never heard of a N55 transmission not holding power. So yeah, there is a huge difference between a syncro becoming worn and slowing down your 1-2 shift than a transmission not being able to hold XXX hp where it would legitimately fail and be no longer useable. I would consider that far from splitting hairs lol. I don't actively follow S55 so I can't even say with certainty if they don't have similar issues with syncros or what is fundamentally different about those transmissions. Happy to be informed though if anyone knows. |
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09-28-2021, 06:48 PM | #10 | |
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Yes, you're definitely splitting hairs. A transmission not functioning is a transmission not functioning. Regardless of failure mode, I wouldn't want to pair that behind a big single - you can if you'd like. Additionally, the N55 version of the 6MT is rated at 450nm of torque vs. 600nm for its N54 predecessor, so yes, the N55 is a weaker - I'd prefer something more robust in when going with a much higher rated turbo. So, let me re-phrase my problem statement and see if we can get off this merry-go-round: "I'd like to put a 68mm Garrett GTX series turbo on my car, but the stock manual transmission is a weak point for the N55. I'd like a transmission that DOESN'T HAVE SYNCRO issues and can handle more power than the N55 version. The feedback on M4 forums is that the MT in those cars doesn't suffer from either issue. Further, it seems like an ideal swap candidate into an F-body as those platforms utilize the same frame. This seems like a good thread to ask this question, as it's literally the title of this thread. Does anyone have any feedback on that topic?" thejeremyman9 if you'd like to start a thread debate on the merits of the N55 6MT, you're certainly more then welcomed to; however, this particular thread is about the S55 6MT as a swap candidate - again, see thread title. |
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09-28-2021, 07:06 PM | #11 | ||
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Also if you have any threads or documentation on the N55 trans failing to hold power would be interested to read those. The 8AT is similarly rated for 450nm but is pushed far further without issue. I read basically every single post in the N55 technical forums and browse the others and haven't ever seen anyone post about an N55 trans breaking due to torque/power level. By no means saying it doesn't exist, legitimately asking for examples so i am informed on the topic. |
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03-08-2022, 11:55 AM | #13 |
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Subscribed as I'm looking to do the same to my n20 (nearing 400whp and want 550whp which brings torque with it).
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03-09-2022, 04:42 PM | #14 | |
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I haven't yet, my synchros are holding up just fine at 89K miles on a Stage 1 tune - although, I don't dog the car either. However, the moment my syncros fail, I'll be doing this exact swap. When that happens, I'll pop back into this thread. |
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03-09-2022, 04:45 PM | #15 |
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I'm faily confident the M3/M4 6MT is a straight bolt-in behind an N55; however, I've done zero research on the plausibility of this swap behind an N20.
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03-09-2022, 09:39 PM | #16 | |
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MY13: TTE400 Stage 2 turbo.
e80 tune by Navardi Tuned. 380 whp/360 wheel torque stock block Build Thread: https://f30.bimmerpost.com/forums/sh....php?t=1742413 IG + YT: Sqwin_n20 |
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11-23-2022, 12:22 PM | #17 |
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FYI Im researching this trans (GS6-45BZ out of m2/m3/m4) as a candidate for my auto->manual conversion on my 6bolt e90 335i (n54). What I've found out is that it will definitely bolt up, however the bell housing for the M trans is slight bigger (compared to the gs6-45bz on the f30 n55 6mt cars) to accomodate the larger clutch/flywheel. I believe the overall transmission length is longer as well, so that might complicate driveshaft and shifter compatibility. Durability and strength on this transmission is better than the f30 trans, has better 1-2 synchro, however not sure what else is has been upgraded internally (possibly bigger shafts maybe). Because of the larger bellhousing, I am not 100% sure about fitment in e90/f30 chassis, I'd imagine there would be no issue, from what I examined via photos on ebay, the bellhousings are only slightly different dimensionally.
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02-25-2024, 02:48 AM | #18 |
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What was the outcome? I ask because I apparently picked up the variant of the GS6 45BZ with the longer bellhousing by mistake for my 2011 e90 335i as a direct replacement. I started my own thread on this issue here.
Last edited by xquatch; 02-26-2024 at 03:54 PM.. |
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02-25-2024, 12:20 PM | #19 | |
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