Charles421 wrote:Some cars have a 1st gear lockout when engages after a certain speed. Mine does.
In the unlikely situation I'm moving at a crawl where 2nd is too high, I'll move the shifter from N > 1. However don't just ram the shifter forwards; I push it against the gear until it goes in on its own.
Never heard of a lockout for 1st gear. Are you sure it's just not the normal resistance you'd feel on any manual trans car?
If you're putting pressure on the gear shifter and waiting for the "lockout" to allow you into 1st gear, I think what might really be happening is that you're causing the synchros to work (by putting pressure on the gear shifter) harder until you can actually select 1st gear. That's probably not the best way to ensure a long life for your synchros.
Charles421 wrote:Some cars have a 1st gear lockout when engages after a certain speed. Mine does.
WHAT? I've never heard of such a thing. It may feel like it won't shift into first above a certain speed, but that is not a lockout, just a shortage of synchro capacity.
'08 Jeep Liberty 6-Speed MT - "Last of the Mohicans"
Charles421 wrote:After some looking into, that is correct, it is a lack of synchro capacity. ~36 MPH in my car, which is redline in 1st.
Edit: hm i think all modern cars w/ synchros would have this ... it's not a "feature" per my BMW's manual then.
The important thing that you have to realize is that you really should avoid doing it. What's happening when you put pressure on the gear shifter towards 1st gear is that the synchros are working hard to match shaft speeds. Once the synchros have done their job, the trans will shift into 1st gear. But doing that is hard on the synchros and will eventually wear them out.
If one, or two, were going to write a specification for a purchased transmission, they might show a series of curves, representing shift time vs shift force, to cover upshifting and downshifting into each gear (well, maybe not upshifting into 1st and maybe not downshifting into 6th, right?), while specifying the speed of the transmission output shaft and the moment of angular inertia of the clutch disk.
Transmissions can be designed that are capable of downshifting into 1st gear at the equivalent of 80 mph road speed, which would result in the clutch disk being spun apart. A transmission designed this way would also allow for low shift efforts and very long synchronizer life during more moderate usage.
'08 Jeep Liberty 6-Speed MT - "Last of the Mohicans"
Rope-Pusher wrote:If one, or two, were going to write a specification for a purchased transmission, they might show a series of curves, representing shift time vs shift force, to cover upshifting and downshifting into each gear (well, maybe not upshifting into 1st and maybe not downshifting into 6th, right?), while specifying the speed of the transmission output shaft and the moment of angular inertia of the clutch disk.
Transmissions can be designed that are capable of downshifting into 1st gear at the equivalent of 80 mph road speed, which would result in the clutch disk being spun apart. A transmission designed this way would also allow for low shift efforts and very long synchronizer life during more moderate usage.
For the record, the only point I'm trying to make is that it's a good thing that Charles421 mentioned his 1st gear "lockout" because we've only helped him understand that when he's applying pressure to the gearshift lever towards 1st gear at speed, he's causing excessive wear to his synchronizers. If he hadn't brought it up in the first place, he might have continued without realizing the wear that he's causing. I can see how a newer manual trans driver might think that there's a "lockout" design feature and that he should just push against the "lockout" until it "releases"
I think it's good that we've helped him (and anyone else who might not have known) understand what's happening when he's downshifting into 1st in that manner.
Shadow wrote:The important thing that you have to realize is that you really should avoid doing it. What's happening when you put pressure on the gear shifter towards 1st gear is that the synchros are working hard to match shaft speeds. Once the synchros have done their job, the trans will shift into 1st gear. But doing that is hard on the synchros and will eventually wear them out.
I avoid using 1st gear as much as I can; I only use it to get moving. I only downshift into it when absolutely necessary e.g. 2nd is not enough. So ~3 MPH.
But I appreciate the explanations anyway, thanks guys.
I still don't know anything about basketball though.
2011 BMW E92 335i: Le Mans Blue, M Sport, 6MT w/ CDV Mod, BMW Performance Exhaust + Style 269 19" Wheels
