Shifting down into 1st problem...

[1996ek1]

Shuddering is at very low speed. Like 8km, its just too low for second im pretty sure... nothing wrong there....

[1996ek1]

Doesnt that mean going down gears, from anygear will ruin the syncros?
Besides, im not releasing clutch... i just dont see how it works....

[Mr_will]

Doesnt that mean going down gears, from anygear will ruin the syncros?
Besides, im not releasing clutch... i just dont see how it works....

ok here we go:

(nb all the RPM's are for illustrative purposes, please dont reply saying errr 4000rpm in this gear at this speed is wrong, it doesnt matter)

say youre going 60kmh - in 4th gear, at 2500rpm. you put the clutch in, and change down (when i say change down, i mean leave the clutch OUT and just move the gearstick) from 4th to 3rd. the rpm for 3rd at 60kmh is 3500rpm. therefore your sycnro's have to deal with that 1000rpm difference in order to have a smooth gearchange. they adjust the speed of the input shaft so that the gears are spinning at the same speed when they lock together.

the fact that you have the clutch in is irrelevant, the gearbox still has to do the work.

when you add the clutch into the equation, you can get excessive clutch wear, when the clutch has to adjust the different in flywheel speed to the road speed.

hope this helps

[1996ek1]

Yea man, that helps a fair bit acctually, thanks for that. (to Mr will)

Leaves me with 1 question

So why is it okay to do it when slowing down, say 4th to 3rd, then 3rd to 2nd, but you just cant do it with 2nd to first? even at real low RPM.

Or is it due to the fact that my syncros are wearing out from being old, and i can only notice it when trying to shift into first gear?

[Mr_will]

Yea man, that helps a fair bit acctually, thanks for that. (to Mr will)

Leaves me with 1 question

So why is it okay to do it when slowing down, say 4th to 3rd, then 3rd to 2nd, but you just cant do it with 2nd to first? even at real low RPM.

Or is it due to the fact that my syncros are wearing out from being old, and i can only notice it when trying to shift into first gear?

no youre right, in order from harder to easiest changes to double clutch it is 5th-4th, 4th-3rd, 3rd-2nd, 2nd-1st, so you are not alone in thinking that.

this will be a fairly lame explanation, but here you go - it is my understanding that gear ratios are the main difference, but im perfectly willing to stand corrected on this point

- the difference between the ratios gets narrower as you go up the gears, such that in terms of RPM, there is a greater difference between being in 1st and second, compared to 2nd and 3rd, and so on.

as a result, its a bit harder to match the revs because the current input speed, and the required input speed are further apart. since you can only estimate (unless youre damn good at doing maths in your head) chances are you'll get it wrong sometimes and not get a smooth shift

[1996ek1]

yea thanks for that. This makes more sense to me...

I plan on changing to EJ8 gearbox, and i WONT be doing 2nd - 1st shifts again, untill stopped

[SeverAMV]

your first gear's top speed is generally around 60% of your second gear's top speed. ie, 40-70, 50-90, 60-100. so the revs nearly double to synchronise properly.

think of it this way, when you're not on the clutch, you're dealing with the gears, when you're on the clutch, you're dealing with the synchros.

first and second tend to be straight-cut rather than angle-cut, but i think that only makes a difference to the sound of the gear rather than the actual engaging.

when you're rev matching with the throttle blipping, dont try to be spot on with the revs, just go like 100-300 revs higher. when you factor in human reaction time, it ends up being perfect.

[bennjamin]

when you're rev matching with the throttle blipping, dont try to be spot on with the revs, just go like 100-300 revs higher. when you factor in human reaction time, it ends up being perfect.

This is what synchromesh was developed for.


Constant-mesh and Synchromesh Gears

[Mr_will]

This is what synchromesh was developed for.


Constant-mesh and Synchromesh Gears

yes well thats all very well and good, but the point at issue here is what can we do to minimise the wear on the sychromesh.

[B18cEG]

Try this, when driving you drop into third, then second, now your slowing down ready to put it into first, while in second push the clutch and rest the gear stick into first position but dont force it in too hard, now just hold it there and give it like a double rev (just tap it a bit) to match the gear speeds and it should kind of fall in place into first, try that then report back to HQ.

[steve88]

i can only shift into 1st if im going really slow, and it makes it pretty hard, but i never do it anyway cause i was told by driving instructor its ****ed for the gearbox, you should roll and stop in 2nd apparently

[B18cEG]

true that