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2Addicts | BMW 2-Series forum Technical Topics N55 (M235i) Engine, Transmission, Exhaust, Tuning 2nd Gear grind. maybe synchros?

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      04-12-2019, 08:37 AM   #1
slow_f22
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2nd Gear grind. maybe synchros?

If anyone has any knowledge that could help me that would be great. whenever i shift from 1st to 2nd gear from 4800 RPM to redline i get a loud grind and some friction. this grind seems to happen even if the clutch is all the way in and i shift slowly it grinds but not nearly as violent but still happens. anytime i shift below 4500 rpm it doesn't grind. i drive a 2015 m235i manual trans. about 40k miles. is there any known solution to fixing the grind? it only happens 1st to 2nd ive never had it 3rd to 2nd. thinking of trying a transmission oil change and trying redline shockproof, others have used that and had success. if anyone has any thoughts on this that could help at all that would be greatly appreciated
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      04-12-2019, 09:02 AM   #2
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Unfortunately the 1-2 syncros are failing and the only fix is replacing the transmission as there are no rebuild kits. Fluid won't help things. It's a somewhat common issue with any 2012+ BMW using the ZF 6MT (M cars, M235, most F series 3s and 4s).

A refurbished M235 6MT is $3,200-3,600 from BMW plus you might as well replace the dual mass flywheel and clutch while you're at it. You're likely looking at $6K USD all in. It REALLY sucks and is the only major repair I worry would with my M235. I would consider begging BMW to goodwill some of this repair. It's worth a shot.

If you bought used, the prior owner probably did it in by driving it hard before the fluid was fully warmed. These 6MTs use a pretty robust fluid for hard driving, but it's critical that you give the tranny 10-15 minute warm up before hitting the gears hard as the fluid takes a bit of time to warm up. I avoid hammering a 1-2 shift often as the 1-2 syncro is the weak link.
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      04-12-2019, 09:08 AM   #3
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Sorry to bring the bad news but from my personal experience the only real fix is a transmission replacement (BMW-covered in my case, twice, but I had to go to another dealer) and possibly also a clutch/dual-mass flywheel replacement (got ripped off on that one to the tune of $4800).

Your synchro grind will only get worse until you cannot shift any more. You can only delay the inevitable, which your dealer may try to do by proposing half-measures. Hopefully your dealer won't do that and instead give you a new transmission, good luck.
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      04-12-2019, 10:23 AM   #4
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Originally Posted by Wheelwright View Post
Sorry to bring the bad news but from my personal experience the only real fix is a transmission replacement (BMW-covered in my case, twice, but I had to go to another dealer) and possibly also a clutch/dual-mass flywheel replacement (got ripped off on that one to the tune of $4800).

Your synchro grind will only get worse until you cannot shift any more. You can only delay the inevitable, which your dealer may try to do by proposing half-measures. Hopefully your dealer won't do that and instead give you a new transmission, good luck.
Thanks for the reply, how did you start about getting a new tranny from bmw? Did you call and make an appointment with the parts and service department? If so what did you say? Just that your synchros are failing and need to have it looked at?
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      04-12-2019, 10:27 AM   #5
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Quote:
Originally Posted by slow_f22 View Post
Thanks for the reply, how did you start about getting a new tranny from bmw? Did you call and make an appointment with the parts and service department? If so what did you say? Just that your synchros are failing and need to have it looked at?

Just follow a standard warranty procedure: tell your dealer about the problem and that you want it rectified under warranty, they will do a test-drive with you and hopefully confirm there is indeed a problem, instead of trying to weasel-out. Once you have that confirmation, they should start the ball rolling with BMW.
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      04-12-2019, 10:33 AM   #6
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Quote:
Originally Posted by slow_f22 View Post
Thanks for the reply, how did you start about getting a new tranny from bmw? Did you call and make an appointment with the parts and service department? If so what did you say? Just that your synchros are failing and need to have it looked at?
Is your car still under warranty? Seeing that it's a 2015, my guess is it's not as the warranty is for 4 years/50K miles (whichever comes first) and the car was likely in service in 2014.
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      04-12-2019, 10:42 AM   #7
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Originally Posted by XutvJet View Post
Is your car still under warranty? Seeing that it's a 2015, my guess is it's not as the warranty is for 4 years/50K miles (whichever comes first) and the car was likely in service in 2014.
I need to check on what day the car was purchased to know if it is still in warranty. Itís under 50k miles it just depends when the car was sold so hopefully I can find some info on that and hopefully is still under warranty.
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      04-12-2019, 11:17 AM   #8
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Put some Red Line trans fluid in and feel if any results. Call them for a recommendation. I'd do the fluid change after you'd have the dealer assess the situation.

https://www.redlineoil.com/heavy-shockproof


Probably one of these https://www.redlineoil.com/gear-oil-...-transmissions

Last edited by ScottSinger; 04-12-2019 at 05:52 PM.
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      04-12-2019, 05:10 PM   #9
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try the redline fluid change first.
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      04-14-2019, 08:56 AM   #10
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try the redline fluid change first.
Don't put redline in if you still have a warranty. It will void your warranty
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      04-14-2019, 11:00 AM   #11
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Quote:
Originally Posted by arhoads335i View Post
Quote:
Originally Posted by amw896 View Post
try the redline fluid change first.
Don't put redline in if you still have a warranty. It will void your warranty
u sure? I think as long as it meets spec, should be fine. I dont think warranty says you have to use bmw fluids or the warranty is void...
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      04-14-2019, 08:44 PM   #12
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Originally Posted by arhoads335i View Post
Don't put redline in if you still have a warranty. It will void your warranty
Warranty passed on 1/19 no longer have it anymore
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      04-15-2019, 10:36 AM   #13
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Quote:
Originally Posted by slow_f22 View Post
Warranty passed on 1/19 no longer have it anymore
See if BMW NA will do anything out of goodwill, you are low on mileage and just out of warranty.
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      04-15-2019, 01:02 PM   #14
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Ask for Goodwill assistance before putting not OEM fluid in the 6MT. You DO NOT want to give them any reason to think that the fluid was the issue. Also, the factory fluid is robust and near race grade. It's also why the fluid requires a bit of time to warm up before beating on it.
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