[Littlebear]

Does anyone know if a old style 2-person bleed will work ("Open", "down", "closed", "up", ...(repeat until hard))?

Murf

[Tchao]

Originally Posted by Littlebear

Does anyone know if a old style 2-person bleed will work ("Open", "down", "closed", "up", ...(repeat until hard))?

Murf

I was not successful doing this. Still had a lot air left. Even took the slave off to invert it a few times. Also tried the vacuum method.

You might be able to do the "old style" two person method w/ cylinder prefilled.
But the reverse bleed works best, and is super fast.

[MLJR235]

Originally Posted by Tchao

I was not successful doing this. Still had a lot air left. Even took the slave off to invert it a few times. Also tried the vacuum method.

You might be able to do the "old style" two person method w/ cylinder prefilled.
But the reverse bleed works best, and is super fast.

LOL, same here. You can do the reverse bleed before you bolt it up which is way easier.

Take it from the OP and me, you will save time, effort, and a whole lot of cursing if you just do it with a syringe. Same as Tchao, I was not able to effectively bleed it doing it the traditional way.

Reverse bleeding is actually really easy. Just have someone help you take out brake fluid from the reservoir as it fills up due to you pumping in new fluid from the slave side. Easy as pie!

[esoj37]

Thanks, OP! This one will be one of my future mods.

[Daytona_550]

Originally Posted by LMLLOPEZ

Just finished up this install using the exact instructions put forth by the OP. Doing the reverse bleed method is a must and fail-proof way to effectively bleed your clutch line 100%. YOu will need a syringe type device to do it but it is well worth it, TRUST ME! lol.

Results are just as advertised. Off the line starts are way more predictable and honestly, the clutch feels "correct" now. No more hit and miss engagement points which are more annoying than words can express. ANyway, this a must-do mod for anyone who has ever had second thoughts as to why they got the manual trans on their late series bimmer. Cheers OP you deserve it

Totally agree on the improvement to clutch engagement. 1st to 2nd shifts are much smoother for me. I didn't venture into doing it myself (no lift) but I had it done by a local indy shop while installing the AS SSK. Highly recommend it.

[MLJR235]

To give people a visual, here is an OEM slave off a '15 M235I. Notice the tiny opening our fluid is supposed to travel through

[pkiledj]

Little off topic but along the same lines (ha!) as removing the CDV. I removed the CDV - washer and rubber - no leaks, and I installed an ultimate clutch pedal, and lots of spacers on the clutch stop. Great! Cut clutch pedal travel in half and no more ambiguous engagement point. My question: for those of you who have removed the spring off the clutch pedal, did your pedal get stiffer? I'm not referring to the small light return spring, I mean the larger spring behind the clutch pedal.

I moved the spring to the middle position on the UCP. It was an improvement over stock but clutch still feels a little artificially springy.

[BMW DIY Guy]

I am loving this thread.. 6MT driver my whole life and 1st and 2nd still occasionally feel weird or not a smooth shift in my F32. I have to seriously look at this.

[BMW DIY Guy]

and then I found this.. can't decide if this is a good way of doing this or not candidly.

[XutvJet]

I really really want to do this mod, but I also know BMW did the CDV for good reason in the turbo cars. The turbo motors generate so much more torque than the naturally aspirated motors of the past and the ZF 6MT really hasn't been upgraded except for stronger syncros on the 1-2 and 2-3. All this added torque, especially on modded cars, teamed with the torque multiplication of the gears themselves, can put a real strain on the syncros and gears on shifts. If you're in the habit of slamming the 1-2 and 2-3 shifts, this mod may not be for you if you want the 6MT to last as it's not serviceable and parts are not available. Your only option is a rebuilt 6MT from BMW or a used one.

[Tchao]

Originally Posted by XutvJet

I really really want to do this mod, but I also know BMW did the CDV for good reason in the turbo cars. The turbo motors generate so much more torque than the naturally aspirated motors of the past and the ZF 6MT really hasn't been upgraded except for stronger syncros on the 1-2 and 2-3. All this added torque, especially on modded cars, teamed with the torque multiplication of the gears themselves, can put a real strain on the syncros and gears on shifts.

BMW put the CDV on cars wayyyy before any turbo cars were born. Its to help drivers shift smoother.

If you're in the habit of slamming the 1-2 and 2-3 shifts, this mod may not be for you

If you are in the habit of slamming gears this IS THE MOD for you. Since you cannot slam gears otherwise, as you just slip and burn the clutch. Dont even think about it if youre modded.

[Tchao]

Originally Posted by BMW DIY Guy

and then I found this.. can't decide if this is a good way of doing this or not candidly.

My way is much easier. Plus you keep the stock slave in case you want to revert back to stock. Its only $60.

[BMW DIY Guy]

Originally Posted by Tchao

BMW put the CDV on cars wayyyy before any turbo cars were born. Its to help drivers shift smoother.

If you are in the habit of slamming gears this IS THE MOD for you. Since you cannot slam gears otherwise, as you just slip and burn the clutch. Dont even think about it if youre modded.

So DONT do this if you are modded?

[MacklinUSOB]

Originally Posted by BMW DIY Guy

So DONT do this if you are modded?

Slamming gears is bad for long term reliability with or without it. BMW also has put these on cars with the smallest motors not because they're afraid of gearboxes blowing up... it's about smoothness and "luxury". If you know how to drive stick and have the mechanical sympathy you need in any other MT car don't even hesitate.

[kern417]

Originally Posted by BMW DIY Guy

and then I found this.. can't decide if this is a good way of doing this or not candidly.

That's my vid . I made a video based on methods used in the original CDV thread. People also use a pick tool or even drill it out (I've done that on previous cars where it can't be simply removed), but that requires completely removing the slave. I did it this way specifically because I didn't want to unbolt the slave, and it's free. It doesn't damage anything, you just need the screw to remove it easily.

Also you shouldn't need to do the reverse bleed method if you don't remove the slave. If you already have the slave removed, just manually pump the slave if you have an issue getting it filled. That'll get all the air out, then top off the reservoir. Otherwise a regular passive bleed should work.

Originally Posted by BMW DIY Guy

So DONT do this if you are modded?

At the end of the day it's a nice mod to smooth out shifts, but it puts the drivetrain more at your mercy. Drive smart and it won't do anything negative. It basically allows you to drive the car hard when you want to, at the expense of allowing your car to take the abuse when you make mistakes.

[BMW DIY Guy]

Originally Posted by kern417

That's my vid . I made a video based on methods used in the original CDV thread. People also use a pick tool or even drill it out (I've done that on previous cars where it can't be simply removed), but that requires completely removing the slave. I did it this way specifically because I didn't want to unbolt the slave, and it's free. It doesn't damage anything, you just need the screw to remove it easily.

Also you shouldn't need to do the reverse bleed method if you don't remove the slave. If you already have the slave removed, just manually pump the slave if you have an issue getting it filled. That'll get all the air out, then top off the reservoir. Otherwise a regular passive bleed should work.

At the end of the day it's a nice mod to smooth out shifts, but it puts the drivetrain more at your mercy. Drive smart and it won't do anything negative. It basically allows you to drive the car hard when you want to, at the expense of allowing your car to take the abuse when you make mistakes.

Nice!! Awesome you are on here.. so if you dont unbolt the slave, just pull the line then pick out the CDV, you dont even have to bleed it??

[kern417]

Originally Posted by BMW DIY Guy

Nice!! Awesome you are on here.. so if you dont unbolt the slave, just pull the line then pick out the CDV, you dont even have to bleed it??

Still bleed, but it'll be much easier than putting a completely empty slave in it's place. If you do it fast, you'll just get a few drips of fluid if any.

[XutvJet]

Originally Posted by Tchao

BMW put the CDV on cars wayyyy before any turbo cars were born. Its to help drivers shift smoother.

If you are in the habit of slamming gears this IS THE MOD for you. Since you cannot slam gears otherwise, as you just slip and burn the clutch. Dont even think about it if youre modded.

I'm well aware that the CDV was put in prior BMW cars. Yes, some of the design is intended to make clutch engagement smoother, but the primary intent is to reduce driveline shock on hard shifts. Yes, the CDV can cause additional wear on the clutch, but it is far cheaper to replace a clutch than the transmission. BMW is covering their butt for cars still under warranty as it gives them some control. Lots of other MTs on the market have CDVs.

We all know the 1-2 syncros on the ZF 6MT fail often, even in stock 3/4 series, M235/240, and M2/3/4 cars. The syncro issue isn't the CDV. It's the torque of these turbo motors. Remove the CDV and you increase the engagement action of the clutch on the shifts. Instead of the CDV allowing the clutch to absorb the driveline shock, more of that shock is transmitted directly to the transmission including the syncros.

I rarely slam the 1-2 on my M235 6MT which has a catted DP and Dinan Stage 2. I've also never experienced any slippage on hard 1-2 and 2-3 shifts.

If and when I do the CDV, I sure as hell won't be slamming the 1-2. Plus, there really isn't a situation I can think of short of 1/4 mile racing where slamming the 1-2 is necessary.

[kern417]

Originally Posted by XutvJet

I'm well aware that the CDV was put in prior BMW cars. Yes, some of the design is intended to make clutch engagement smoother, but the primary intent is to reduce driveline shock on hard shifts. Yes, the CDV can cause additional wear on the clutch, but it is far cheaper to replace a clutch than the transmission. BMW is covering their butt for cars still under warranty as it gives them some control. Lots of other MTs on the market have CDVs.

We all know the 1-2 syncros on the ZF 6MT fail often, even in stock 3/4 series, M235/240, and M2/3/4 cars. The syncro issue isn't the CDV. It's the torque of these turbo motors. Remove the CDV and you increase the engagement action of the clutch on the shifts. Instead of the CDV allowing the clutch to absorb the driveline shock, more of that shock is transmitted directly to the transmission including the syncros.

I rarely slam the 1-2 on my M235 6MT which has a catted DP and Dinan Stage 2. I've also never experienced any slippage on hard 1-2 and 2-3 shifts.

If and when I do the CDV, I sure as hell won't be slamming the 1-2. Plus, there really isn't a situation I can think of short of 1/4 mile racing where slamming the 1-2 is necessary.

For me WOT 1-2 shifts were actually very smooth prior to removing the CDV. I could get the tires to chirp, even on stock tune. But it was partial throttle acceleration around town where the 1-2 shift was jerky. I've only been locked out of gear a few times and usually it was WOT 2-3 or 3-4. But for some reason hard 1-2 never gave me issues. I think because subconsciously I shift 1-2 a little slower, but still feels good. 3-4 is lightening fast, so makes sense I'd get locked out more easily.

Have any links for the synchro issues? This is the first I've heard of that.

[XutvJet]

Originally Posted by kern417

Have any links for the synchro issues? This is the first I've heard of that.

Do a Google search of 2nd gear grind, 6MT replacement, etc. Numerous automotive publications have also reported 2nd gear grinding on their 6MT M2 and M3 test cars. Overall, the ZF 6MT is a stout transmission, but it's 1-2 syncro is its Achilles heal.

[Tchao]

Originally Posted by BMW DIY Guy

So DONT do this if you are modded?

I meant slamming gears with mods on stock CDV will slip like a mofo.
You def need this CDV delete. No way you can shift fast without smoking the clutch and glazing it.

For example back in the day just on JB4 map 1 or 2, I would already slip the clutch if I were to shift fast. Now a days with MHD/BM3 Ethanol tunes, you will forsure super glaze your clutch if you tried to shift fast with the CDV.


I dont usually slam gears, but when I want to, like in a drag situation, I want to know I can.

[renizer]

hey there,
so i know this is the F30 forum but just to get this right - the F series (except 1, 3, 4 series and X5/6 it seems, when looking up the slave cyl) has the same slave cyl as just about all the E series cars minus X5/X6 E.
So it seems to me, the cars that have this slave cyl have the CDV located in the stock line - like my E91: http://bmwfans.info/parts-catalog/E9...lutch_control/
Imo the diagram clearly shows the CDV in the line? So no CDV in the slave needed.

However, for the exceptions, like F30, the line does not have a CDV in the line. If you combine those CDV-less lines with CDV-less "E" slave -> no more CDV

Oh and I'm pretty sure BMW did this for drivetrain protection and longevity just as much as for "improved" driveability and NVH for ppl who prefer this laggy indirect shit over "sheer driving pleasure"