BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > E90/E92 M3 Technical Topics > Engine, Transmission, Exhaust, Drivetrain, ECU Software Modifications
 
Strasse Wheels
Post Reply
 
Thread Tools Search this Thread
      11-27-2009, 06:22 AM   #23
MMMorish
Just call me J.J. McClure
MMMorish's Avatar
Canada
58
Rep
2,836
Posts

 
Drives: E92 M3 & C4 Corvette
Join Date: Sep 2008
Location: Toronto

iTrader: (5)

Your tranny is fine. I had TONS of grinds in my first tranny, that thing was a lemon. But after BMW replaced it, I had a "lazy" grind happen to me once between 1st-2nd at about 3k rpm as well. The car is fine! The syncros in these trannies are made of CF, so they should withstand a lot of abuse.

Hey Harris, take your car on a test drive with a BMW tech and replicate the problem, they'll change your tranny without any questions asked. My second tranny is not plagued by the 1st-2nd grind. Thank God!
__________________
MODS: Meisterschaft GT Racing Exhaust / BMC Air Filter / UUC SSK & DSSR (Modded)/ RPI Scoops / Passport SRX Hardwired / Custom Wrap 3M Clearbra / 20% Tint / 50% Windshield Tint / Key Hole Delete / Matted Out Accessories / VRS Type II Diffuser / Smoked Reflectors / Euphoria 6K LED Interior Lights / Rear Fog Light Mod / 6000K HID's / 6500K LUX H8 Angel Eyes / RDash License Plate LED Kit / LED Xenon Reverse Lights
"M3 drivers have no friends"
Appreciate 0
      11-27-2009, 09:49 AM   #24
J08M3
Major General
J08M3's Avatar
United_States
102
Rep
6,012
Posts

 
Drives: 2011 M3 COUPE
Join Date: May 2008
Location: NEW YORK

iTrader: (8)

Quote:
Originally Posted by elp_jc View Post

By the way, removing the spring on '08 cars (they only have one) reportedly creates problems with the cruise as the cruise deactivate switch is all the way to the top of the clutch pedal travel, and removing the spring causes the pedal to drop enough as not to allow cruise to engage, or disengages at the least provocation. Folks doing that mod should test their cruise. Owners of '09 cars can always install the '08 spring for better feel. The '08 clutch spring seems like the best compromise. Besides the cruise issue, folks who drive in heavy traffic might not appreciate a heavy clutch over the long run. A matter of personal preference.
I've had my spring removed for over a year and not one issue with cruise and I use cruise all the time on the highway. There is another spring that holds the pedal all the way up.

Also, the clutch in my opinion is not heavy at all without the spring, it's just more linear in feel.
__________________
Appreciate 0
      11-27-2009, 05:08 PM   #25
elp_jc
Brigadier General
United_States
79
Rep
4,910
Posts

 
Drives: .
Join Date: May 2008
Location: .

iTrader: (0)

Quote:
Originally Posted by MMMorish View Post
But after BMW replaced it, I had a "lazy" grind happen to me once between 1st-2nd at about 3k rpm as well. The car is fine! The syncros in these trannies are made of CF, so they should withstand a lot of abuse.
Thanks for the encouraging words . So the grinding sound is a synchro hitting a gear then? Need to find an exploded view of this Getrag tranny to familiarize myself with it; google didn't work.

Quote:
Originally Posted by J08M3 View Post
I've had my spring removed for over a year and not one issue with cruise and I use cruise all the time on the highway. There is another spring that holds the pedal all the way up. Also, the clutch in my opinion is not heavy at all without the spring, it's just more linear in feel.
Good info man . The post I read probably didn't have that spring reinstalled. I haven't investigated that mod since I'm happy with the clutch feel myself. Thanks.
Appreciate 0
      11-29-2009, 04:52 PM   #26
dougman
Second Lieutenant
dougman's Avatar
9
Rep
228
Posts

 
Drives: '07 E92 328 --> 2010 E92 M3!
Join Date: Apr 2007
Location: Bay Area

iTrader: (0)

Quote:
Originally Posted by MMMorish View Post
Your tranny is fine. I had TONS of grinds in my first tranny, that thing was a lemon. But after BMW replaced it, I had a "lazy" grind happen to me once between 1st-2nd at about 3k rpm as well. The car is fine! The syncros in these trannies are made of CF, so they should withstand a lot of abuse.

Hey Harris, take your car on a test drive with a BMW tech and replicate the problem, they'll change your tranny without any questions asked. My second tranny is not plagued by the 1st-2nd grind. Thank God!
CF Syncros??? I don't think so. CF would be a terrible friction material, and would shred and leave fibers in the tranny as it wears. Syncros are brass or steel.

The gears themselves are always in mesh. The syncros are cones (see last pic and you can see the cone) that speed up or slow down the shafts to allow the "dogs" to mesh, at which point the gears are locked to the appropriate shaft.

Syncros prevent the interlocking teeth of the collar from engaging until it is spinning at the same speed as the one it is going to mesh against.

When syncros wear down/wear out, they either slip or don't engage soon enough to get the collars spinning at the same speed before the teeth engage.

When you "grind your gears" you're actually hearing the collar grinding. The gears themselves are always in mesh so you're not hurting them. There is still the potential for damage over time, but it's not the same as

Here's a link:

http://auto.howstuffworks.com/transmission1.htm
Attached Images
   
Appreciate 0
      11-29-2009, 05:03 PM   #27
J08M3
Major General
J08M3's Avatar
United_States
102
Rep
6,012
Posts

 
Drives: 2011 M3 COUPE
Join Date: May 2008
Location: NEW YORK

iTrader: (8)

Most syncros I know of are brass, or some material softer than the gears, this way any grinding that happens damages the syncro not the gear.
__________________
Appreciate 0
      12-02-2009, 03:14 PM   #28
elp_jc
Brigadier General
United_States
79
Rep
4,910
Posts

 
Drives: .
Join Date: May 2008
Location: .

iTrader: (0)

Quote:
Originally Posted by J08M3 View Post
Most syncros I know of are brass, or some material softer than the gears, this way any grinding that happens damages the syncro not the gear.
I don't think the synchros have teeth; do they? So they only wear if you push/pull on the knob while driving, no?
Only collars and gears (not the teeth but the 'female' dogs) seem to be able to grind. Now the question is if both the collar and gear could be damaged while grinding, or one is supposed to 'sacrifice' itself for the other . When a gear 'jumps' back to neutral, means the collar 'dogs' are rounded from grinding, and can't keep itself mated to the gear. I guess it doesn't matter if it's just one or both components, as tranny has to be opened up in that case. And although gear teeth are unaffected, the affected gear has to be replaced anyway due to worn dogs.

My new question is how synchros can wear prematurely if knob is never held while driving. Hopefully both the gears and collars are strong enough to withstand some abuse, as it's practically impossible not to grind a gear at least a few times in the life of the tranny. Thank you all for your contributions .
Appreciate 0
      12-02-2009, 06:44 PM   #29
Philritter21
Second Lieutenant
Philritter21's Avatar
United_States
7
Rep
208
Posts

 
Drives: MR E90 M3
Join Date: Nov 2006
Location: Midwest

iTrader: (0)

:
__________________
Melbourne Red E90 M3 - E39 540i

The original user of the animated Bert and Ernie avatar. Except no substitutes.
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 08:47 AM.




m3post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST