[Vegetable]

Hi all. I have a 2014 435i with MPPK. About 2 months ago I noticed that I would occasionally get a grind when up-shifting quickly at redline between 1st and 2nd gears. Now, it is absolutely impossible for me to up-shift from 1st to 2nd at redline without a horrible grinding noise. Would this typically be the clutch or some other mechanism. This only happens when up-shifting at or just below redline. Down-shifting into 2nd from 3rd or up-shifting below 6,000 RPM results in no grinding. This doesn't happen with any other gear. For example I can quickly upshift from 2nd to 3rd at redline without any grind.

Thanks

[AudiA4]

It's a bad 1-2 synchro...a common problem with BMW 6MT. When I purchased mine, 2 of the 3 335's I test drove had a bad synchro. I didn't discover it in the one I purchased until the way home. The dealer replaced it under warranty at no cost.

[Vegetable]

Thanks AudiA4, I figured that would be the cause, but had a few mechanics say that the clutch was probably bad.. Luckily I bought the 100,000 mile warranty as I am at 75,000 miles

[AudiA4]

Originally Posted by Vegetable

Thanks AudiA4, I figured that would be the cause, but had a few mechanics say that the clutch was probably bad.. Luckily I bought the 100,000 mile warranty as I am at 75,000 miles

Lucky indeed, as the dealer told me it's normally $8,000 for a new transmission.

[ae4007]

Just had my transmission replaced a month ago for that exact same problem. Definitely bad synchro, glad I had CPO warranty.

[DrifterX]

Originally Posted by AudiA4

It's a bad 1-2 synchro...a common problem with BMW 6MT. When I purchased mine, 2 of the 3 335's I test drove had a bad synchro. I didn't discover it in the one I purchased until the way home. The dealer replaced it under warranty at no cost.

How did you demonstrate the issue to successfully get it replaced under warranty?

First few times I did a hard 1->2 redline shift, there was a grind but I thought maybe I shifted too quickly so I've been delaying my clutch release more conservatively since then.

Entering second gear does feel a bit clunky at times even shifting from other gears.

[aigochamaloh]

Interesting, I don't have an issue going into 2nd, but I get an almost "lockout" feeling going from 2nd to 3rd or 4th sometimes. I have to be very patient and wait for engine RPM to fall to match and it'll go in smoothly. This is not very confidence inspiring if it's a common issue with synchros.

[AudiA4]

Originally Posted by DrifterX

How did you demonstrate the issue to successfully get it replaced under warranty?

First few times I did a hard 1->2 redline shift, there was a grind but I thought maybe I shifted too quickly so I've been delaying my clutch release more conservatively since then.

Entering second gear does feel a bit clunky at times even shifting from other gears.

One drive around the block with the service manager was all it took...only 90 seconds in, he said, "Yep, bad synchro. Congratulations, you get a new transmission."

Generally, you do in fact have to shift aggressively at a higher RPM to induce the problem, as the higher the RPM the more difficult it is for the synchros to do their thing. If you're trying to replicate the problem for the dealer, certainly don't baby it! Or let them drive it...they know their stuff.

[jeffro535]

Yeah, they had to replace mine for a bad 2-3 synchro at 14k miles. double check the reverse switch (back up lights/camera) before taking the car back, as apparently the switch casing is pretty fragile and they can hoark it up when they swap it from the old transmission to the new one. I got the car home and was backing out of the the garage and was like hmmm something's missing here.

[AudiA4]

Originally Posted by J35 - N52

Maybe if you weren't constantly shifting at redline you wouldn't of ruined your synchro.

Who said he was "constantly" shifting at redline? Even if he were, it shouldn't do that...this is a sign of a mechanical failure.

[enjoythemusic]

Originally Posted by AudiA4

Who said he was "constantly" shifting at redline? Even if he were, it shouldn't do that...this is a sign of a mechanical failure.

Agreed. Hopefully the car is still under warranty as indeed it does sound like a synchro issue.

[Vegetable]

For those of you who have had your gearbox replaced, is the replacement just as prone to 2nd gear synchro failure, or has there been improvements? I'm just wondering because my car was diagnosed with having a bad 2nd gear Synchro, but what's the point if the replacement is going to be just as bad?

[XutvJet]

I also wonder how many people are shifting hard on cold transmissions and before the tranny oil is warmed up on a stone cold motor. It takes a solid 10+ minutes of driving before the dry-sump equipped 6MT found in the N55/B58 gets up to temp. Beat on the car before tranny is up to temp and you can damage a syncro on a hard and abusive high rpm on a very high torque gear change like the 1-2. Once the syncro is damaged, it will exhibit the issue, warmed tranny or not.

As far as I know, the M235 uses the same 6MT as the F3X 6MT, but in the 2014-2016 M235 literature, it notes that the M235 has beefed up lower gear syncros. Perhaps the new F3X are using the upgraded M235 6MT? I have heard of a couple of cases on M235 with damaged syncros, but all those cars were pushing quite a bit more power than stock and were raced.

[AudiA4]

Originally Posted by Vegetable

For those of you who have had your gearbox replaced, is the replacement just as prone to 2nd gear synchro failure, or has there been improvements? I'm just wondering because my car was diagnosed with having a bad 2nd gear Synchro, but what's the point if the replacement is going to be just as bad?

No problems so far with my new transmission. One would assume they are "improved" in some way, but not necessarily. Even the most perfectly designed and manufactured components aren't perfect, and some "fail rate" is to be expected.

[Vegetable]

Originally Posted by AudiA4

No problems so far with my new transmission. One would assume they are "improved" in some way, but not necessarily. Even the most perfectly designed and manufactured components aren't perfect, and some "fail rate" is to be expected.

Audi, did you have the clutch/flywheel changed at the same time?

[AudiA4]

Originally Posted by Vegetable

Audi, did you have the clutch/flywheel changed at the same time?

Not to my knowledge.

[isloth]

What other symptoms is known for a bad synchro?

Sometimes, when I shift from 1 to 2, I could hear like a shutter sound of something. This happens when I depress the clutch pedal. From 2 to 3, 3 to 4 and so forth, I do not hear or could replicate that shutter sound. Any ideas? I really don't know what to make of it because it's my first time owning and driving a 6MT.

[AudiA4]

Originally Posted by isloth

What other symptoms is known for a bad synchro?

Sometimes, when I shift from 1 to 2, I could hear like a shutter sound of something. This happens when I depress the clutch pedal. From 2 to 3, 3 to 4 and so forth, I do not hear or could replicate that shutter sound. Any ideas? I really don't know what to make of it because it's my first time owning and driving a 6MT.

If it "grinds" (you'll both hear and feel this in the gear shift) when you shift, it's a bad synchro.

[isloth]

Originally Posted by AudiA4

If it "grinds" (you'll both hear and feel this in the gear shift) when you shift, it's a bad synchro.

Oh I see. During shifts, 1 to 2, haven't really noticed any grinding. Only when depress clutch, once in awhile I hear something but maybe it is just the mechanics of clutch and flywheel working under normal operation.

Perhaps, next time CBS lights on for service, I'll bring this up to the SA. Overall, car drives good, no issues so far. I do not upshift at high RPMs or anywhere near the redline.

[Dan203]

I think I was starting to get this on my 135i before I got rid of it. (one of the reasons I did) A few times near the end I would shift from 1 to 2 and it would pop out of gear. I had been driving it for 8 years, but it only had 30K miles on it.

[XKxRome0ox]

i've had my '16 328i 6mt for about 15 months now
i've taken my car into 2 different dealership about 9-10 times for the "grinding" when shifting into 2nd gear .............
service technicians are unable to duplicate
i'm unable to duplicate the problem when with a tech as well
it's really frustrating

[Vegetable]

Originally Posted by AudiA4

Not to my knowledge.

I hope they did, but it seems like you had yours done early on in your car's life so maybe it wasn't needed. I now have 75,000 miles on my 435, so it's recommended that I get a new clutch/flywheel (while it's out) which comes to $2300 that isn't covered under my warranty. Ouch!