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      03-24-2016, 02:59 AM   #1
kb135
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3rd gear grinds when shifting slow, but smooth when shifting fast

Hi all. I have searched for days on various forums (to no avail) to try to ascertain why the following occurs: Please help.

The problem: Whether cold or warmed up, 1-2 and 2-3 shifts (mostly 2-3) will feel like a mild-moderate 'grrr' when engaging.

Description of symptom (grind): It isn't a typical audible grind, but more felt through the gear stick, with slight hesitation to engage.
Over 3500+ rpm it is fairly smooth with virtually no grind felt.

Other investigations: I have also shifted at different rates: slow and gentle (grind felt), swift (less grind), racing (virtually imperceptible). If stopped with clutch in, there is NO grind on engaging any gears and they do so smoothly which leads me to believe the clutch is disengaging fully on depression. And yes, I am depressing it fully when driving.

The scene: 2009 135i 6MT, Redline D6 ATF fluid 3000kms ago, CDV delete, no lengthened clutch stop (other mods too but are engine and cosmetic).

Why is this so?
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      03-24-2016, 06:14 AM   #2
Dackelone
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I would bleed the clutch again. I had to do mine three times before I got all the air out. You might also look into reverse bleeding the slave cylinder from under the car upwards. Let gravity help get those air bubbles out!

Another option might be to try BG's Syncro-Shift gear oil. It can help on marginally worn trans/syncro's.
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      03-24-2016, 06:42 AM   #3
The Wind Breezes
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You have worn synchros probably from someone driving the car improperly. It happens. Don't try shifting your car without a clutch or anything (I love this, it's fun) and it'll probably last longer than you keep the vehicle.
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      03-24-2016, 09:00 AM   #4
kb135
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Yeah thanks for the replies guys. Will give the above-mentioned a try and see how it goes. I'm pretty easy on my MTs but its just disheartening when you're cruising gently and there's a grinding feel, and its only got 80,000kms.

Also forgot to mention, interestingly this only happens on upshifts, not downshifts.
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      03-24-2016, 06:11 PM   #5
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Does it feel like it catches briefly while you're moving into gear and doesn't fully engage and thus it grinds when you let the clutch back out?

did you always have this problem?
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      03-26-2016, 10:19 AM   #6
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Quote:
Originally Posted by lowbudgethero View Post
Does it feel like it catches briefly while you're moving into gear and doesn't fully engage and thus it grinds when you let the clutch back out?

did you always have this problem?
It makes a 'grrr' sensation (felt, not heard and only a split-second duration), on upshift 2-3 but engages fully. There is no grinding on clutch release or depression. Though it is noted that the upshift takes longer while the synchros work.
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      03-26-2016, 11:57 AM   #7
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Quote:
Originally Posted by kb135 View Post
It makes a 'grrr' sensation (felt, not heard and only a split-second duration), on upshift 2-3 but engages fully. There is no grinding on clutch release or depression. Though it is noted that the upshift takes longer while the synchros work.
You have a worn blocker ring in the 3-4 synchro assembly. It's the most common wear item in a manual transmission. It's responsible for matching the selected gears speed to the output shaft speed, allowing the syncro ring to slide into the clutching teeth, and engage the selected gear smoothly. The feeling you get is the clutching teeth "bouncing" off of the syncro ring. This is how gear grind starts, and can usually be alleviated with a fluid swap. I recommend RedLine MTL as a substitute.
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      04-10-2016, 12:19 PM   #8
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Thank you all kindly for your inputs. I will be changing out my fluid (from a recently changed Redline D4 ATF, I might add, which probably made things worse, or at the very best did nothing) and flushing and bleeding the clutch and brakes as well. Will let you know how I fare.
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      04-29-2019, 07:44 PM   #9
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Did you find a cause/solution?

I have a new 2019 m240i, with 3k miles, and the exact same problem you described, and aren't sure what route to pursue.

Thanks!
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      07-22-2019, 09:59 AM   #10
LaurentZo
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Any updates on your situation, OP? I have a very similar issue on my 2008 135i, and I would very much like to know if you succeeded in reducing the grind, so that I can do the same!
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