[mtoo]

For you MT drivers, why is it that when I try to downshift from 3rd gear to 2nd gear, occasionally the transmission blocks me from putting the car in that gear?

I can understand if it was preventing me from money shifting, but it happens at all sorts of slower speeds that would not cause the RPM to jump over the redline.

Example 1: Getting onto a highway in 3rd at like 30-40mph, and trying to drop to 2nd gear to accelerate into traffic.

Example 2: Driving 30-40mph in 3rd gear approaching a school zone, and then wanting to downshift into 2nd to slow down.

Both of the above situations never seem to work unless I double declutch, but by that point in time I've already spent seconds trying to get the thing in gear.

If I turn off rev match, it does not block me from going into gear in those situations anymore, and the syncros or throttle blip works fine to keep me moving (although less convenient).

What gives?

[ixD9]

There's no lockout in the transmission that would prevent you from shifting into second. Are you maybe being too aggro with the shift lever? Syncros need time to match so it's best to just exert a bit of pressure and let it slip into gear versus trying to jam it into gear as fast as possible. If you're way too aggressive you can even bend the shifter fork which could cause issues with shifting until you get it straightened back out.

[Squidget]

Originally Posted by ixD9

There's no lockout in the transmission that would prevent you from shifting into second. Are you maybe being too aggro with the shift lever? Syncros need time to match so it's best to just exert a bit of pressure and let it slip into gear versus trying to jam it into gear as fast as possible. If you're way too aggressive you can even bend the shifter fork which could cause issues with shifting until you get it straightened back out.

This. There's no intelligence/nannies in the MT, if you are being blocked it's a physical component getting jammed somewhere it's not supposed to be.

I guess it's also possible your synchros have a defect, but if the 2nd gear collar was messed up, I assume* you'd feel it on 1 -> 2 shift, also.

*disclaimer: very much not a mechanic.

[mtoo]

Originally Posted by ixD9

There's no lockout in the transmission that would prevent you from shifting into second. Are you maybe being too aggro with the shift lever? Syncros need time to match so it's best to just exert a bit of pressure and let it slip into gear versus trying to jam it into gear as fast as possible. If you're way too aggressive you can even bend the shifter fork which could cause issues with shifting until you get it straightened back out.

I don't think I'm being too aggressive, so when it 'blocks' me from engaging 2nd gear, I don't force the issue. I never have trouble going from 1st to 2nd gear.

So are we sure that Rev Match doesn't have any system in place that's causing this? Unless I'm imagining it, it seems to behave differently with Rev Match On vs Rev Match Off. I'll keep experimenting.

[robopp]

Originally Posted by mtoo

I don't think I'm being too aggressive, so when it 'blocks' me from engaging 2nd gear, I don't force the issue. I never have trouble going from 1st to 2nd gear.

So are we sure that Rev Match doesn't have any system in place that's causing this? Unless I'm imagining it, it seems to behave differently with Rev Match On vs Rev Match Off. I'll keep experimenting.

Rev match just blips the throttle. Not sure about BMW, but Porsche has sensors to know what gear you’re in and uses that to apply throttle. The actual shifting is purely mechanical.