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2Addicts | BMW 2-Series forum Technical Topics B58 (M240i) Engine, Transmission, Exhaust, Tuning 2nd gear grind in manual transmission

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      04-11-2016, 03:28 PM   #45
Wheelwright
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Quote:
Originally Posted by B_Rice View Post
Are you depressing the clutch all the way to when you shift? I've found out that the grab point is pretty much anything above the floor.
I always depress clutch all the way, no exceptions. And the clutch grab point is supposed to be constant in BMW, that's the whole idea behind design called SAC (self-adjusting clutch) which those cars use. Maybe you mean "clutch feel" which is non-existent in BMW because conventional clutch linkage has been replaced by a feedback-free hydraulic system.

And indeed this hydraulic system might have been the root cause of my ordeal, if for whatever reason it was too slow to disengage clutch from the flywheel upon pressing the clutch pedal. When this happens an excessive torque gets transmitted onto the gearbox synchro eventually destroying it and thus the entire transmission.

Last edited by Wheelwright; 04-11-2016 at 03:59 PM..
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      04-11-2016, 03:53 PM   #46
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I have had this problem, but it is not unique to this car. The "grinding" you are hearing is the syncromesh trying to match the transmission and engine speed from 1 to 2. As with most cars, the largest gear-ratio difference is between 1 and 2 -- the ratio in 1 is always much greater than 2, than say 2 is greater than 3. This is why you get this grinding sound between 1 and 2, but normally not 2 and 3, 3 and 4, etc. The sound you hear is the synchromesh being overwhelmed trying to match speeds.

This isn't so much of a problem with the gearbox as it is just a limitation on this kind of car -- go google this problem, and a lot of people (E46 M3 included) have this issue. This is not a drag car -- it does not like it when you slam shift from 1 to 2. You can, but your synchros will go out. This is a road course car, where you never shift lower than second gear.

Try this: shift quickly, but smoothly. Don't just try to jam the gear lever into 2 as you brush 7000 rpm. Let the lever slide into place. Slow down just a tad and let the synchros do their job.

I know this may sound disappointing re: "but its a BMW, it should be able to shift at high RPMs." Indeed, it can, but smoothly (at least from 1 to 2).
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      04-11-2016, 03:54 PM   #47
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I think you have been unlucky with some parts being out of tolerance here.

I have to say in addition the that 6sp MT in the two series is not a bad one, just too imprecise for 'as fast as humanly possible' shifting.

In my old Civic type R it was a case of slap it through the gears as fast as you physically can, the car could happily keep up. In the BMW you have to flow through the gears with deliberate movements.

I find the car rewards smooth inputs in general, the transmission most so.
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      04-11-2016, 03:58 PM   #48
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Quote:
Originally Posted by Boosted_six View Post
I think you have been unlucky with some parts being out of tolerance here.

I have to say in addition the that 6sp MT in the two series is not a bad one, just too imprecise for 'as fast as humanly possible' shifting.

In my old Civic type R it was a case of slap it through the gears as fast as you physically can, the car could happily keep up. In the BMW you have to flow through the gears with deliberate movements.

I find the car rewards smooth inputs in general, the transmission most so.
Honda transmissions are famous for being able to just manhandle the gears and get what you want out of it -- S2000 and Civic Si being the prime examples. This transmission, while very good, is not that good. It's not a production defect, it's just a design choice/flaw. Getting a new BMW transmission will not let you slam shift this car from 1 to 2.
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      04-11-2016, 04:01 PM   #49
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Quote:
Originally Posted by Liquidpaper View Post
Honda transmissions are famous for being able to just manhandle the gears and get what you want out of it -- S2000 and Civic Si being the prime examples. This transmission, while very good, is not that good. It's not a production defect, it's just a design choice/flaw. Getting a new BMW transmission will not let you slam shift this car from 1 to 2.
Sorry my post was directed at OP

I agree, this gearbox is not a slammer
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      04-11-2016, 04:01 PM   #50
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Quote:
Originally Posted by Boosted_six View Post
Sorry my post was directed at OP

I agree, this gearbox is not a slammer
I know, just thought I would agree with you.
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      04-11-2016, 04:17 PM   #51
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Quote:
Originally Posted by Liquidpaper View Post
This isn't so much of a problem with the gearbox as it is just a limitation on this kind of car -- go google this problem, and a lot of people (E46 M3 included) have this issue. This is not a drag car -- it does not like it when you slam shift from 1 to 2. You can, but your synchros will go out. This is a road course car, where you never shift lower than second gear.
I never "slammed" the shift, I merely waited less than I usually do between 1st and 2nd while my revs hovered around 5000rpm. Any car should be able to take it with ease, in fact my brother's old rusty Mazda never had problems with dynamic 1st-2nd shifts. Shouldn't we expect the same from an M-car ?

Let's stop making apologies for those fragile and under-engineered BMW transmission and clutch components. BMW is not stupid: it is done on purpose because not only are those components designed fragile BMW dealers later charge Ferrari prices to fix them. See the pattern here ? Sorry for not drinking BMW coolaid but I expect more from a car with M-letter in its name.
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      04-11-2016, 04:20 PM   #52
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Quote:
Originally Posted by Wheelwright View Post
I never "slammed" the shift, I merely waited less than I usually do between 1st and 2nd while my revs hovered around 5000rpm. Any car should be able to take it with ease, in fact my brother's old rusty Mazda never had problems with dynamic 1st-2nd shifts. Shouldn't we expect the same from an M-car ?

Let's stop making apologies for those fragile and under-engineered BMW transmission and clutch components. BMW is not stupid: it is done on purpose because not only are those components designed fragile BMW dealers later charge Ferrari prices to fix them. See the pattern here ? Sorry for not drinking BMW coolaid but I expect more from a car with M-letter in its name.
Not making apologies, that's just what they chose to do -- its a design defect, not a manufacturing defect. Would it be nice if the transmission could handle that kind of shift. Of course. Does it? No.
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      04-11-2016, 04:24 PM   #53
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I don't think the transmission is under engineered as such, Just imprecise.

On a fast as humanly possible change from 2nd to 3rd I sometimes find 5th!

You need to be accurate rather than hero
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      04-11-2016, 09:51 PM   #54
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I just read C&D test of BMW M2 ( http://www.caranddriver.com/reviews/...-valley-review ) and this quote caught my attention: "Quick shifts into second gear include a crunch..". There is little hope for M235i and BMW in general if even their track-ready vehicles don't have robust gearboxes.
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      04-11-2016, 11:04 PM   #55
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Quote:
Originally Posted by Wheelwright View Post
I just read C&D test of BMW M2 ( http://www.caranddriver.com/reviews/...-valley-review ) and this quote caught my attention: "Quick shifts into second gear include a crunch..". There is little hope for M235i and BMW in general if even their track-ready vehicles don't have robust gearboxes.

This is crazy...... And I feel your pain on this whole ordeal.. It seems like this happens to a few select people and they go through hell for a year or so... This is complete bullshit..

A 6MT should be able to handle TWICE the horsepower thrown at it.. At the very least..

I really hope that BMWCA makes this right.. Please keep us informed, and thank you for the valuable information..
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      04-12-2016, 08:10 AM   #56
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Just as an FYI, I went in to BMW for a normal service interval, mentioned that I have also suffered from this when the transmission is cold/low revs. Good news is this, there will be a TSB for these transmission the service guys know about it, so presuming your cars drivetrain isn't modded, BMW will be taking care of this issue soon.
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      04-12-2016, 08:22 AM   #57
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Good info Prazision! Thx!
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      04-12-2016, 03:12 PM   #58
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One thing I've noticed about this 6MT is that the tranny fluid viscosity must lean more towards a mild race-spec package because the fluid requires quite some time to get up to temp. I say that because the tranny can be slightly resistant on occasion to get into 3rd and 4th and the 1-2 can be a bit notchy when cold. I notice this most when the tranny is stone cold and in colder weather. Based on what I'm seeing, the tranny needs a good 10-15 minutes of driving before it becomes smooth shifting. To account for this, I don't rush the shifting nor do I force anything if I feel an inkling of resistance.

Like with many direct injection turbos and their fat powerbands, taking 1st to redline really isn't the fastest way to accelerate. You'll actually be a bit quicker short-shifting the 1-2 at 6000rpms vs 7000rpms. This helps load up the turbo at the start of 2nd.

I can't say I've ever felt any resistance slamming the 1-2 shift, but I don't do it often at all and if I do, I've been driving for 20+ minutes before doing so. In almost all occasions where I'm feeling frisky, I'll wind out 1st to 5500-6000rpms and quickly (not slam it) shift to 2nd. There's really no point to slamming the 1-2 unless you're drag racing under the timers. With the 8AT cars and in manual mode, you can clearly feel the torque management system softening a WOT 1-2 shift to preserve transmission longevity.

As for those with power modifications, you should really be careful about letting the tranny get up to temp and not slamming the 1-2 routinely. That extra 50-100+ wtq will certainly take it's toll on the synchronizer over time especially with all the torque multiplication in 1st and 2nd gears.

What does confuse me greatly are some of the repair costs I've seen thrown around regarding the 6MT. Per the getBMWparts.com website, the M235 6MT (rebuilt) is around $2,650 and you get a $600 core back. The flywheel and clutch assembly are around $1,500 total, I believe. If you were replace the bell housing (don't know why you'd need to), the all in cost for 6MT, clutch, flywheel, accessory parts, etc. is around $5,000. So where in the hell are these crazy costs coming from?

And for those wondering, the ZF 8AT is $7,000.

Last edited by XutvJet; 04-12-2016 at 03:20 PM..
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      05-06-2016, 08:11 PM   #59
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So finally I got my second manual transmission replaced at another dealer hassle-free. As I suspected: when a synchro first starts grinding the transmission is basically on borrowed time until it no longer shifts into the affected gear. I was told I have to take it easy for about 1000km but after that "I can drive hard because that's what BMW M cars are designed for". Not based on my experience, they aren't, I am not rolling dice on replacing another transmission/clutch/flywheel any more.
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      05-06-2016, 10:12 PM   #60
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Quote:
Originally Posted by Wheelwright View Post
So finally I got my second manual transmission replaced at another dealer hassle-free. As I suspected: when a synchro first starts grinding the transmission is basically on borrowed time until it no longer shifts into the affected gear. I was told I have to take it easy for about 1000km but after that "I can drive hard because that's what BMW M cars are designed for". Not based on my experience, they aren't, I am not rolling dice on replacing another transmission/clutch/flywheel any more.
If things don't work out, consider lemoning the car.
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      05-07-2016, 11:22 PM   #61
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were you using a taller clutch stop? After reading this im debating removing mine or decreasing the length of my clutch stop. I installed it minus 1 spacer. I feel as if i short clutch anyways though due to the long throw. Anyone else using the clutchstop?

I also realized that the tranny is notchy and stiff before it gets to a good temp. I wonder if a fluid swap and possibly to a different brand would possibly prevent or cure some of notchy feel.
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      05-08-2016, 08:30 AM   #62
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No clutchstop for me, my car is 100% bone stock. Besides, I don't think it is a good idea: 2-series has hydraulic clutch lines providing zero clutch engagement feel, on top of that if you shorten the clutch-pedal throw you're asking for trouble.

I find this manual transmission less stiff at cold temperatures than some other cars I had so I think this behaviour is pretty normal. Personally I would never change a transmission fluid to a different brand because BMW/dealer can deny your transmission warranty.
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      05-08-2016, 06:20 PM   #63
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I want to add to this thread also. I too have this second gear grinding issue when shifting from 1st to 2nd gear at 5000+ rpm.
It usually happens within 5 minutes of starting the car and less frequent as the car gets fully warmed up.
I think the clutch disengagement/engagement doesn't match the clutch pedal in real time.
I am experiencing this at the frequency about once a day now.

This gearbox also has problem downshifting to 2nd rapidly due to the reverse gear gate getting in the way.

This car will be returned after lease is over. I am done with BMW manual gearbox, my old E46 manual transmission did not have any of these issues.
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      05-08-2016, 09:34 PM   #64
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Quote:
Originally Posted by Merc for hire View Post
I want to add to this thread also. I too have this second gear grinding issue when shifting from 1st to 2nd gear at 5000+ rpm.
It usually happens within 5 minutes of starting the car and less frequent as the car gets fully warmed up.
I think the clutch disengagement/engagement doesn't match the clutch pedal in real time.
I am experiencing this at the frequency about once a day now.

This gearbox also has problem downshifting to 2nd rapidly due to the reverse gear gate getting in the way.

This car will be returned after lease is over. I am done with BMW manual gearbox, my old E46 manual transmission did not have any of these issues.
everyone here can thank the CDV valve for the feel, or lack of and the delay for many shifts in 1/2. I am working on modifying mine next. Ironically if you know how to drive a manual, the more likely you will have issues with cdv valve equipped cars.
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      05-08-2016, 10:17 PM   #65
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Quote:
Originally Posted by Pparana View Post
everyone here can thank the CDV valve for the feel, or lack of and the delay for many shifts in 1/2. I am working on modifying mine next. Ironically if you know how to drive a manual, the more likely you will have issues with cdv valve equipped cars.
Ah yes, the CDV. I remember that from the E46 era as well. Removing it was the first mod people do.
Thankfully the early 1999-2000 E46s didn't have this, and my was a 2000.
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      05-09-2016, 03:39 PM   #66
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This is a disappointing read. Does anyone know if there has been a specific redesign for the synchros, and if so, when it went into effect?

FWIW, other manufacturers have encountered this problem. They discovered that the fluid used in the tranny can help. So, while I'm sure it is not an approved fluid for BMWs, something like GM Friction Modified Synchromesh or the "reformulated" Honda tranny fluid may clear this problem right up. Both manufacturers had problems with synchros and both came out with "new" tranny fluids:

http://www.amazon.com/88900399-Synch.../dp/B00BK7M2VW

http://www.amazon.com/Genuine-Honda-.../dp/B001IWL1O8

The friction modified fluids are actually LESS slippery than typical transmission oils. Thus, the synchro can grab sooner and get up to speed faster. I had the second gear grind in my Honda S2000. The different fluid pretty much made it go away.
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