Cold weather clunk debate...lets figure this out!

[Shadow]

Okay, end of summer might not be a bad time to discuss this topic...so here goes:

As most of us are aware, it's not uncommon for a gearbox to develop "clunky" shifts in cold temps. This most often happens when the gear oil inside the gearbox is cold, and is most evident during the 1-2 shift. Some easy fixes include changing out the gear oil for something a bit different, or simply waiting for the clunk to disappear as the gearbox oil heats up over time.

So why does this happen? Well, my understanding is that the gear oil isn't as effective cold as it is when hot, as far as being able to "spin up" the synchro quick enough to result in a smooth shift. I'm guessing that the higher viscosity of the oil when it is cold means that the synchro spins up to speed slower, which can result in a clunky shift.

Here's the question (and the debate I've been having with a friend of mine)--- When driving with a clunky gear engagement, is any damage (or even excessive wear) being done to the synchronizer? Does anyone know for sure? I mentioned this once before on the forum a long time ago, but I don't think we ever came to a solid conclusion either way. I have my thoughts, but I want to wait to see the general consensus on the forum.

[Rope-Pusher]

Okay, end of summer might not be a bad time to discuss this topic...so here goes:

As most of us are aware, it's not uncommon for a gearbox to develop "clunky" shifts in cold temps. This most often happens when the gear oil inside the gearbox is cold, and is most evident during the 1-2 shift. Some easy fixes include changing out the gear oil for something a bit different, or simply waiting for the clunk to disappear as the gearbox oil heats up over time.

So why does this happen? Well, my understanding is that the gear oil isn't as effective cold as it is when hot, as far as being able to "spin up" the synchro quick enough to result in a smooth shift. I'm guessing that the higher viscosity of the oil when it is cold means that the synchro spins up to speed slower, which can result in a clunky shift.

Here's the question (and the debate I've been having with a friend of mine)--- When driving with a clunky gear engagement, is any damage (or even excessive wear) being done to the synchronizer? Does anyone know for sure? I mentioned this once before on the forum a long time ago, but I don't think we ever came to a solid conclusion either way. I have my thoughts, but I want to wait to see the general consensus on the forum.

Nobody has ever done an A to B comparison.

[Shadow]

Nobody has ever done an A to B comparison.

Not even sure what that means.

[Shadow]

So...nobody has a clue? Really?

An educated guess? An opinion?

LOLOLOL

[DarkPilot]

I'd imagine there would be more wear than running at nominal temps but not a substantial amount more as usually the trans warms up pretty quickly and minimizes the time in the extra wear zone.

[Shadow]

I'd imagine there would be more wear than running at nominal temps but not a substantial amount more as usually the trans warms up pretty quickly and minimizes the time in the extra wear zone.

What kind of wear do you mean? Synchronizers?

[comingbackdown]

I usually take my shifts slow when it's "cold enough", then again it was so goddammned cold here last year that even with newish fluid synchros were kicking and screaming bloody murder and my clutch felt like pushing a brick wall and the pedal took two seconds to come back up after a shift. You know it's a different kind of winter when normally you hate the cold and the moment it's above freezing you're like "Yay, it's cold but it's on its way up!" and last year I walked out and spent eight minutes in 32* weather in my work uniform with no jacket and was like "God damn it's warm out here!"

[Shadow]

Even with a brand new Audi, I still got a bit of a notchy shift from 1-2 when the temps got really cold. So I swapped out the original gear oil for some Redline stuff and it was a big improvement for sure. It's still not perfect though, but I can't really complain because it's not very bad at all anymore. I just wish the shifting felt the same in winter as it does in the summer, meaning smooth and easy all the time.

[daleadbull]

Even with a brand new Audi, I still got a bit of a notchy shift from 1-2 when the temps got really cold. So I swapped out the original gear oil for some Redline stuff and it was a big improvement for sure. It's still not perfect though, but I can't really complain because it's not very bad at all anymore. I just wish the shifting felt the same in winter as it does in the summer, meaning smooth and easy all the time.

Even in the summer, my first few shifts are a little notchy when the car is cold. It seems to quickly warm up though and shifting becomes smoother. During the winter, this warm up phase takes a little longer.

Like you said, its just the nature of the gear oil. Similar to how to how the engine oil needs to warm up when you start up the car. Changing out the oil with something that has better cold weather performance would help but would warm weather performance or longevity suffer? Who knows? So I just stick with the manufacture recommendation and accept the fact that the shifting will be a little rougher until it gets up to temp. This may mean some negligible synchro wear, so be it.

[Shadow]

Even in the summer, my first few shifts are a little notchy when the car is cold. It seems to quickly warm up though and shifting becomes smoother. During the winter, this warm up phase takes a little longer.

Like you said, its just the nature of the gear oil. Similar to how to how the engine oil needs to warm up when you start up the car. Changing out the oil with something that has better cold weather performance would help but would warm weather performance or longevity suffer? Who knows? So I just stick with the manufacture recommendation and accept the fact that the shifting will be a little rougher until it gets up to temp. This may mean some negligible synchro wear, so be it.

With the Redline, even the first shift in the morning is butter smooth in the warm summer temps.

As far as warm weather protection/performance/longevity, I don't have any concerns. If anything, if there is any possibility of that, I'd think that it would be more than offset by the wear & tear that you put on the synchros with the notchy shifting that occurs with the factory fill.

So anyway, the cat's out of the bag now.....my opinion is that notchy shifts are in fact damaging to the synchros. It just makes sense in my mind. Even if you don't hear the typical grind sound that you get with a missed shift, I still think the notchy shift isn't doing any favors for your synchros.

[anmasher]

This is how it works as far as I understand it.

When the fluid (gear oil, ATF, etc. depending on transmission) is colder it is thicker and has a stronger film strength. The harsher shifts are caused because the blocker ring has a harder time cutting through the oil to lock on to the gear train and bring it to speed. A synthetic fluid helps significantly. Castrol TranSynd in my case performed wonderfully during the past winter even when the clutch pedal was basically unresponsive.

I would suspect that there is not any or at least not excessive wear in these instances since the synchro blocker is just cutting through an oil film and the shift is not harsh because of greatly mismatched speeds. For example when you shift from 5th to 2nd it is harsher/harder/stiffer/whatever because the synchro ring has to speed up the entire gear line drastically to whatever the engine RPM would be in 2nd at the given speed. There will be *some* wear because the synchro is fighting a huge inertial load. In cold weather it isn't doing that even though the shift may feel the same. I can't prove any of this so take it with a grain of sand..