[xquatch]

I have a 2011 335i 6MT with the 2nd gear synchro issue. I picked up a used 6MT locally, but now that I have both units out of the car side-by-side, the replacement (donor) unit has a couple of differences.

Here are some data points:

• Bellhousing is about 1 inch longer
• Trailing gimble yoke is about .25 inches longer/thicker
• Bolt pattern is compatible, but you will need to swap out the OEM aluminum M12 x 90mm mounting bolts for the shorter S55 steel M12 x 75mm bolts (pn 23001222893). Torque to 66NM.
• My original OEM unit is stamped 1089 401 084 on the bellhousing, and 1089 401 051 on the main gear housing
• The QRL codes on my original OEM unit are S027613833 10893011071A on the gearbox and RS06GSP1089301079 3SS028813845RSEOT on the paper tag on the bellhousing
• The QRL codes on the donor unit are 1089 301 146 S720419627 S on the gearbox and 06 P1089301161 3S7160320068 on the paper tag on the bellhousing
• The donor unit is stamped 1089 401 161 on the bellhousing, and 1089 401 145 on the main gear housing
• There are a few other subtle differences on the outside of the case
• The input shaft inside the bellhousing is the same shape as the original, but longer and appears it will align with stock clutch and flywheel
• Not clear if the stock slave cylinder will work or if I need to source a different one to accommodate the longer reach within the bellhousing
• OEM shifter/linkage will be off by about 1 inch
• Driveline will likely be too long, or need to source a shorter one
• Flywheel bolt torque specs appears to be 120NM based on a few videos I found. Can anyone confirm that with ISTA?
• Clutch pressure plate bolt torque should be 30-34 NM. See also this F8x ISTA reference if you have stretch bolts.
• Seattle area.

Based on the above casing numbers, the doner transmission appears to be used in the F8x M2, M3, M4, and correlates to model GS6-45BZ (variant SHBS) and part number 23007858800.

The flywheel part number is 21212283028, and it is characterized by its raised mounting pillars for the corresponding twin disk manual clutch (part number 21212284234).

References

• Images posted here
• Related thread: S55 6spd Transmission swap
• Related thread: N54 to N55 6MT swap
  Potential to use N54 shift arm and linkage, and driveshaft to compensate for the ~1 inch delta in bellhousing length.
• Clutch DIY tips and tricks
• 6MT Gear Sensor vs Reverse Switch
• [URL"https://www.e90post.com/forums/showthread.php?t=2011936"]6MT Swap w/ good info about driveshaft requirements[/URL]

Thanks!

[ppointer]

I use realoem dot com for parts numbers. Not certain if the parts yard knows what they are talking about.

[xquatch]

Originally Posted by ppointer

I use realoem dot com for parts numbers. Not certain if the parts yard knows what they are talking about.

Thank you, I like realoem as well. What appears to be elusive is any cross reference to the casing numbers. Both units I have no longer have readable stickers so I have to rely on those.

I am in parallel trying to source another unit that is plug and play.

[M-technik-3]

Have you tried looking up info via the QRL codes on the transmissions? I see no mention of that.

[xquatch]

Originally Posted by M-technik-3

Have you tried looking up info via the QRL codes on the transmissions? I see no mention of that.

• The QRL codes on my original OEM unit are S027613833 10893011071A on the gearbox (embossed tag) and RS06GSP1089301079 3SS028813845RSEOT on the bellhousing (paper tag)
• The QRL codes on the donor unit are 1089 301 146 S720419627 S on the gearbox (embossed) and 06 P1089301161 3S7160320068 on the paper tag on the bellhousing (paper)

Pics for both added to the album link

[ppointer]

Originally Posted by xquatch

Thank you, I like realoem as well. What appears to be elusive is any cross reference to the casing numbers. Both units I have no longer have readable stickers so I have to rely on those.

I am in parallel trying to source another unit that is plug and play.

About a year ago a close friend bought my e91 and set about to convert to MT. We found a complete set on eBay (pedals, plumbing, shifter, transmission, diff, drive shaft, etc.). Just mentioning it in case you did not consider eBay as a possible source. BTW, the conversion was a success.

[xquatch]

So still need to resolve the following:

• My original e90 335i shift linkage will likely be too short. Over on "s p o o l s t r e e t" at ".../threads/gs6-45bz-variants-differences-and-compatibility.8292/" it was suggested that the linkage for an e90 53BZ might work. Need to verify.
• My stock driveline will be too long, by about 1 inch, so need to source a shorter one. Also suggested that the stock driveline out of an automatic e90 335i should work as it is an inch shorter. Need to verify.
• Assuming the stock clutch/flywheel will work, need to verify if the stock slave cylinder will also work with the longer bellhousing. Would one with a longer arm be needed to accommodate the longer reach within the bellhousing, or would that be achieved through a different pivot arm?
• I do not know how to determine exactly which variant of 45BZ the donor is, as the paper label on the unit is washed out. Does anyone know how to cross reference the casing numbers provided to identify it?

Or also trying to find a stock low-mi/km variant that is plug and play.

.

[xquatch]

A couple updates:

• Regarding which variant of 45BZ donor I have, some units recently hit ebay that list the same QR code of my donor unit (1089 301 161) and they list them as coming out of the F80 F8* M3 M* cars, so this appears to be one of the SH** variants. Anyone have access to ZF aftermarket to cross-reference the QR codes?
• Some think the stock e90 clutch/flywheel will not work with the longer bellhousing. I've found solutions in other forums where people have used longer clutch release bearings to adapt to clutches with different stack heights. I am searching for a potential solution - either another make/model bearing, or a way to fabricate the same.

[xquatch]

I was able to find a very good condition take-off OEM F8* twin disk clutch and flywheel, so just need to tap the hole for the reverse switch and get it all bolted up.

[Malteser_wfj]

This is such a good thread I'm following and enjoying the updates.

Hope it all comes together well!

[xquatch]

Some discrepancy on the bolt torque specs for the flywheel to crank, and pressure plate to flywheel. Both sets of bolts are steel and should have a straight up torque value, but the following values appear to be associated, so it is indeterminate at the moment.

In this video on YT (time stamp 38:25), the flywheel bolts are torqued to 89 ft lb and the pressure plate bolts are torqued to 22-25 ft lb. The car in the video is an N54 E90.

This seems more accurate than this ISTA reference, which seems to imply torque specs for stretch bolts. ¯\_(ツ)_/¯

[xquatch]

One more thing, the bracket (N55 6MT) that goes between the downpipe and transmission will be about 15mm off as the S55 6MT housing's bolt holes are more shallow. Before I either just leave the bracket off, or shim the gap with something, I'm going to see if the bracket for the N55 AMT will work. Preliminary comparison in images suggests it could work. Stay tuned.

• original N55 6MT bracket
• N55 AMT bracket

Update: As a temporary fix, made some spacers that make up the 15mm gap by drilling out a couple of steel cap nuts and then grinding them down to 15mm in height.

[xquatch]

https://www.e90post.com/forums/showthread.php?t=2011936Okay, so we're all locked and loaded and backing out of the garage...



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All gears shift fine, and it only took like 10 days to bleed the air out of the clutch (new slave). Then all of a sudden there's just this grinding noise and the car is not moving. Good thing is I'm literally only 10 feet out of the garage. Short story - driveshaft splines stripped out on the donor AT front half driveshaft I got from local part out.

There are a few e90 AT driveshaft takeoffs (1472mm) on ebay. I can't believe the new OEM price is like $1k+. Not sure if the donor front half was already worn or what. I inspected it before assembly, but I will look closer on future installs.

In the meantime, my back half looks to be undamaged, so I'm going to see if I can make my original 6MT driveshaft work at 1485mm. I've see one other post where they were able to do this, but all future dismounts will require removing the driveshaft at the diff instead of the guibo. Stay tuned.

[cookiemontis]

Xquatch, when I used my factory manual driveshaft swapping from a gs45bz to the longer gs53bz. I did not have to unbolt the driveshaft from the differential.

Typically there is enough room to unbolt the front shaft to guibo and slide it back and out of the rear of the transmission.

When using my original drive shaft, I had to also unbolt the center support bearing in order to slide the shaft back and out of the rear of the transmission. Not a huge deal and my suspicion is bmw uses a shorter shaft for this reason and not due to actual clearance issues where the front and rear shafts mate.

Also I have put over 10k on the car setup like this without issue. No abnormal wear on the center support bearing or clearance issues using the longer driveshaft.

[xquatch]

cookiemontis thanks for that input. I was wondering if the 53BZ and the longer 45BZ would result in the same offset. I'm thinking that the longer variant of the 45BZ (M models) that I've installed is just a bit longer overall and preventing me from using my original driveshaft (1485mm). I tried every angle and contortion and nothing would give me the clearance to get both ends into mounting position.

I've sourced a 2007 335i (pre-LCI) driveshaft (335i AT @ 1453 mm) (PN 26107614433 or 26107558504) that should work. The next possibility might be the 335i N55 LCI AT driveshaft @ 1472mm (PN 26107574678).

I cleaned up the splines on the donor AT shaft that was slipping but that didn't work, still slips.

[xquatch]

Final outcome - installed a used low-mi driveshaft (complete take-off) from a pre-LCI (PN 26107558504 @ 1453mm) and we're back on the road. 2nd gear is smooth and silky. A bit more noise from the F80 DMF, and 1st gear is a bit more audible (more like what I would expect from a MT). No issues in the first 30+ miles of mixed driving, so happy with it so far. If anyone else has questions about this swap just hit me up. The outside of the F80 trans, flywheel and clutch assembly, the other components are the same whether doing this or the 53BZ swap.

One other note, the N54 53BZ gear linkage was about right, but I had to bend the top portion of my stock M 335i short shift lever about 15 degrees forward as well. It worked at first by just putting it in backwards (180 degrees), but then it leaned to the right as some have experienced when doing this accidentally. So, it was either bend it left, or forward. This was due to likely a centimeter or less difference in the length of the link. I got mine from the UK, so maybe there is one that is slightly longer but I was not able to find specs on the "selector rod" beyond the part numbers matching for both US and UK models (PN 25117524722). Alternatively you could buy an adjustable shift rod or fab your own.

[wrevilo]

Great work!

[boostd92]

Thanks for doing all of this!! I have a 2011 E90 N55 MT that lost reverse. I've been driving it anyway (have to be creative parking on hills, parallel, etc) but was just going to bite the bullet and buy a new one (about $4,000 installed at a discount for a new N55 BMW GS6-45BZ).

I have a separate agenda though...

I am FBO PS2 with everything running meth/E50 and my 335is clutch slipped at ~550whp.

I tried a Spec steel SMFW and 2+ clutch and the feel was not for me and it's a sunny day car (not a race car) and the chatter with the A/C on was not cool (I bumped idle and tried fluid mixes, but it was still obnoxious).

The F80 uses a stock DMFW and twin disc clutch that most say will handle 650-700whp (more than my PS2 could ever make) and have stock like engagement and sound.

This should fix all my issues!

Did you ever check the gear ratios? Notice any difference? How does the stock F8x clutch/flywheel feel?

Did you use an F8X slave or an N55 slave?

TIA

[xquatch]

boostd92

Q: Did you ever check the gear ratios? Notice any difference?

AFAIK the gear ratios are the same and I've not noticed any difference there.

Q: How does the stock F8x clutch/flywheel feel?

To date the swap has been solid and feels great. It feels stouter and shifts smoothly. It may not be as quiet at idle as the stock setup, but quiet and smooth as you start rolling. Shifting through the gears is emphatically firmer, snappier. I don't feel like a slight miss might chip off a synchro tooth.

Did you use an F8X slave or an N55 slave?

I used a new F8X slave, but it was identical with the N55 OEM slave.

I have no regrets and I am glad I went this route over spending 4x the money on a new N55 replacement.

[boostd92]

Can you describe what you mean by it being louder at idle?

[xquatch]

Originally Posted by boostd92

Can you describe what you mean by it being louder at idle?

I would describe it as follows. The OEM setup was fairly quiet until it started grinding synchros. After the swap it has just a hint of vibration at idle, which reminds me of all the manual performance cars I've owned in the past, like my E39 M5, 323i Alpina as a couple of examples.

My understanding is that the 335i GS6-45BZ and clutch setup was engineered to be lighter, and as a result quieter. The swap to the stouter SHBS and twin disc clutch just add a bit of feel at idle, and nothing out of the norm. The flywheel is likely also a bit stiffer.

Has anyone out there driven an N55 45BZ 335i manual and also an F8X manual S55 to compare? I assume what I'm trying to describe is the same or stock feel you would have in the F8X M* cars.