Hey guys, I have a question about manual transmissions on general. I know a lot of manufacturers design them so that you cant get into first gear untill a low mph. I was wondering how they acomplish this? Is there some sort of contraption on the synchro? Thanks in advance for any help.

 

i can drop first at 20 mph i just need to rev to like 7500 rpms then hope i rev match, its just that its such a short gear, its like downshifting to second at 55 when you top second at 58

 

If you can get the mainshaft and countershaft spinning at the same speed (accounting for gear ratios), you can shift from any gear to any other at any speed. The trick is that at anything but low speed, the countershaft is being spun at the wrong speed to engage with the mainshaft, unless you rev the **** out of the motor in neutral to get the shaft speeds matched (accounting for gear ratios).

 

Right, but its not like when your doing 90mph you have to rev match to put your shifter into second gear, it will go in with no problem. obviously you wouldnt want to engage the clutch at a speed like that.. but you can still move the shifter into that gear without hesitation...why is it that you cant do the same thing in first?

 

wait, i reread what you posted and i get what your saying dpaton. but why is it that first seems to stand out so much? just because it is the lowest gear?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NathanielH &raquo;</TD></TR><TR><TD CLASS="quote">wait, i reread what you posted and i get what your saying dpaton. but why is it that first seems to stand out so much? just because it is the lowest gear? </TD></TR></TABLE>

Yup.

Numerically higher ratios require a higher rev on the input shaft to match the synchros enough to spin the countershaft up to a speed where the gears will mesh and you can shift.

As for downshifting to 2nd at 90, my trans won't do it without waiting for the countershaft to come up to speed, which takes a little bit of time. There's about 20lbs of metal that needs to be spun between speeds, which is why you sometimes miss a shift that you didn't think you were going to miss.

 

I understand now. Thanks for the help