What is it that prevents selection of 1st gear

[C.slicker]

What is it in a clio and I assume all cars, that prevents you selecting 1st gear at say over 10mph? Also why is this the case for 1st yet you can still select second gear at say 80? Of course you would never release the clutch buy what is it in the car that stops the stick moving into position?

Just interested,

Cheers dudes!

 

[JAY172]

just the synchro baulking up as it cant cope with a selection at that speed for such a low gear.

 

[C.slicker]

But why does it not happen with the other gears?

 

[arj256]

If you match the revs to the speed your traveling. You can in theory then go into 1st at 30 without it jolting forward.

 

[C.slicker]

Yeah, I just don't get why it happens in 1st and not any other gear?

 

[arj256]

As 1st has the lowest gear ratio compared to the other forward gears thus meaning the syncromesh has alot more work to do in comparison to the other gears.

 

[Martin_172]

blip the throttle and it will go in, as for why it does it in first and not any other gear, i dont know just know its the syncro

 

[edde]

If you think about it revs double from second to first roughly. IE 3k in first is 6k in second so gearbox syncros have to get it right from 5th to 4th its not as huge a chnage.

 

[GordonD]

Your gearbox has an input shaft and and output shaft connected together by a number of pairs of gears, one pair of which is meshed together at any one time depending on which gear you've selected. When you push the clutch pedal in the input shaft is disconnected from the engine, but the ouput shaft is always connected to the wheels. When you move the lever to select a gear the syncros for that gear have to force the input shaft to speed up or slow down so the two shafts are spinning at the right speed before the pair of gears can engage.

If you are driving along in fifth and you try to change into fourth the input shaft only has to be speeded up a little bit, so it doesn't take a lot of force to push the lever into that gear. But if you try to change into first it has to be speeded up a lot, so its really hard to push the lever into that gear. Its not that you can't. Its that you have to push really hard. Or do it slowly so the input shaft has time to speed up. Or engage neutral, let the clutch out and blip the engine so it speeds up the input shaft, then press the clutch again and select the lower gear.