[Avanti7]

Hi guys,

I got a manual 2.5 M3 GT. Usually when I shift through the gears, the shifter goes into the gear slot (from neutral) with 1 smooth notch and that's it, like it should in an ideal world. However, sometimes I feel like there is a 2nd notch as the gear leaver travels from neutral into gear. It doesn't grind or get stuck or need any extra effort - it still goes into gear no problem, it's just a feel I get in my hand. So when shifting from neutral into gear, instead of the usual singular "clunk" it feels like a double "clun-clunk".
Here's a video from youtuber MotoMasterX5 where I see/hear the same behaviour. If you pay attention to his downshifts into 2nd, you'll notice that the gear leaver jerks ever so slightly as it goes from neutral into second. It happens at 0:42 and more prominent on 1:18 (Sorry, I can't post links yet):
youtu.be/H6A2YPNl1Qg?t=42
youtu.be/H6A2YPNl1Qg?t=78

Here's the same phenomena on a WRX Subie on 0:31, while shifting into 1st (more prominent) and then 2nd (you can hear it):
youtu.be/2s4fIxvI68M?t=31

Has anyone ever notice that? Is that an issue or am I OCD-ing like crazy here?

If you're still reading:
I noticed this behavior on other cars as well. I used to own a Civic with the same symptoms and I drove my friend's 2018 Mustang with similar feel in the shifter. In 2015 I test drove a 2.0 M3 and it also had the same feel. But I just can't help but wonder - is this normal or do I have an issue with my tranny? Most of the time it happens when downshifting into 2nd and almost never happens if I shift from 1st to 2nd after 3000rpm. So it's almost like the car is asking for revs >
I know a bit about a manual transmissions, so it may just be the gear sleeve sliding over the dog teeth of the gear. The gear is rotating at the same speed as the sleeve (due to the synchro), but there is nothing to align the teeth of the gear to the slots in the sleeve. So that occasional notchiness might be the sleeve hitting the misaligned teeth, aligning them and going in.
Any thoughts?

 

[zero_gravity]

Very normal. The synchros are very good at lining the lock collars up with the dogs on the gears, but are not always perfect. There's a bit of intentional slip in the synchro rings and that is how they do their job. It's just a slight misalignment between the synchro and the gear dogs is all. The lock collar slides onto the synchro ring and that's the first 'clunk'. Second is just the collar making it the rest of the way and locking in the gear. When you only get one, the rings are pretty well perfectly aligned. Keep in mind that these dogs are tapered so this bit of slip is normal and expected at times.

When it doesn't line up quite perfectly like this, if you were to try and let go of the clutch after only the first stop, you'd grind the gear.

This may be difficult to visualise if you've never taken a look inside a manual transmission. There's plenty of educational articles on the internet of how a manual transmission works with pictures. Its very much worth the time if you want to know more.

If you really want to understand this well, you can always get an old transmission and pull it apart. You'll see what I'm talking about very quickly.

With my previous car, I blew a bearing in the trans. Got another one from a junkyard, but I demanded to have the old one returned. Learned a lot from that. I had planned to rebuild it to keep as a spare. The job was easier than I expected, but the cost of parts made it just not worthwhile. By the time I was ready to replace that bearing, the car was getting too old to care about having the spare trans anyway. Turned out the junkyard one was in excellent shape.

By the way, I can confirm first hand that a good synthetic gear oil such as redline will reduce the chances of this.

 

[Avanti7]

Much appreciated, zero_gravity! Thank you for the detailed response.
I can't say I went as far as taking apart an actual transmission, but I did watch a few detailed videos on how they work. What you said makes sense, it's pretty close to what my guess was in the OP.

When it doesn't line up quite perfectly like this, if you were to try and let go of the clutch after only the first stop, you'd grind the gear.

I actually experienced that once in my first car, an 8th Gen Civic (last all-round good Civic gen imo; that was until I found my true love :laugh2. In M3 though, the shifter action is so positive that I can't "catch" it before the second "notch" - the gear follows through and engages anyway. Only when I'm at a stop, shifting into first from neutral, once in a blue moon I feel significant resistance at the second "notch" - my guess is that's when the dogs are in "perfect misalignment" with the collar. I have a hunch that it has to do with the fact that the car is not moving and syncro's don't have a chance to do their job. Never happens when the car is moving.

By the way, I can confirm first hand that a good synthetic gear oil such as redline will reduce the chances of this.

That's awesome! I'll probably do that. Not that it bothers me too much anymore, but it'll probably prolong the life of the tranny anyway, so that alone makes it worth it.