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What Rpm Do You Flat Change At? Double Clutching?

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TUF250 Proficient

TUF250

Posted
Posted

Hi folks,

My GTSt has the typical notchy, crunchy gearbox particually into second from first.

I have just put soem redline oil in it but I want to reduce the wear on it where possilbe. Now I dont want to flat change without the clutch but I thought if I shift at about those revs it might put less strain on the synchros? is this true or not? If it is then what rpm is best first to second?

Also what is the proper way to double clutch? This is my first manual car and I can drive it well normally but still trying get my head around all the rest of it.

sorry for the newbie type questions but I know I will get the right answer here

Thanks

Duncan Grand Master

Duncan

Posted
Posted

well, the simple answer is the synchros are there to look after the gap in revs between gears.

eg if you shift from 1st to 2nd at about 40klm/h you will have to go from 5000rpm to 2500rpm. The quicker you move the gear shift and release the clutch, the less time the engine has to get from 5000 to 2500.

So the best way to look after your gear box is:

1/ back off the throttle

2/ move the shifter from 1st to neutral

3/ let the revs drop from 5000 to 2500 (depends on gears and road speed of course, this is just an example)

4/ move the shifter from neutral to 2nd.

If you do exactly that you will have basically no wear on the synchros...but you will have slow gear changes which is why all gearboxes have synchros these days. If you get the steps above right you also will not have to use the clutch but you may as well incase you miscalculate.

Downchange is the opposite

1/ back off the throttle

2/ move the shifter from 2nd to neutral

3/ blip the throttle to 5000rpm (depends on gears and road speed of course, this is just an example)

4/ move the shifter from neutral to 1st.

Once again, if you get it spot on the shifter will go straight in, and you won't need to use the clutch.

In practice you should be able to do everything above with some practice, just use the clutch in case you get it wrong. Driving like this minimises the wear on the synchros, but once they are stuffed nothing apart from removing the box and replacing them really fixes it.

bubba Grand Master

bubba

Posted
Posted (edited)

Do you mean "rev matching" as opposed to "flat shifting"??

If you're talking about driving it like a crash box, in trucks it's more about roadspeed than revs in a gear (you will change up or down at particular revs but which gear you grab depends on your roadspeed, which in a truck is hugely affected by road gradient), because we have wide powerbands and fewer gears, it's harder to rev match in petrol cars and is by no means an efficient/economical way to drive.

I have had to shift without a clutch when I snapped my fork pivot, was an absolue ass of a thing to do but it was 3am and I had to get it to the workshop.

Edited by bubba
Harey Veteran

Harey

Posted
Posted
Hi folks,

My GTSt has the typical notchy, crunchy gearbox particually into second from first.

I have just put soem redline oil in it but I want to reduce the wear on it where possilbe. Now I dont want to flat change without the clutch but I thought if I shift at about those revs it might put less strain on the synchros? is this true or not? If it is then what rpm is best first to second?

Also what is the proper way to double clutch? This is my first manual car and I can drive it well normally but still trying get my head around all the rest of it.

sorry for the newbie type questions but I know I will get the right answer here

Thanks

Mine is also very notchy from 1st to 2nd. Doesnt crunch but just takes a bit to get in there. Also downshifting from 3rd to 2nd is a bit hard to get in. All other changes are fine, must be something to do with second gear.

I used to change pretty hard, now I take more care.

bubba Grand Master

bubba

Posted
Posted
Mine is also very notchy from 1st to 2nd. Doesnt crunch but just takes a bit to get in there. Also downshifting from 3rd to 2nd is a bit hard to get in. All other changes are fine, must be something to do with second gear.

I used to change pretty hard, now I take more care.

Double de-clutch with a throttle blip and it should go in real nice like. Also works to get it in to 1st gear while rolling.

Deano 1 Mentor

Deano 1

Posted
Posted

dude just use the clutch... your goin to do more damage crunching gears tryin to learn to rev match than you will just using the clutch.

but if you insist goin from 4th to 5th is the easyest one so start there

Trozzle Grand Master

Trozzle

Posted
Posted

I've taught myself to double clutch on up and downshifts, thanks to the shithouse gearbox in the good ol' VL commy....now I'm getting a bit lazy with the skyline, but I certainly change slowly regardless.

I'll only ever throw it through the gears quickly when I'm driving hard, and then I will ALWAYS double clutch.

my box is a little notchy with 1st-2nd, and 2nd-3rd. Downshifts don't feel notchy, just tight. Strangely though, 2nd-3rd isn't a crunchy kinda feeling, but as it goes from neutral to third without the double-clutch, it feels like 3rd says "naww f*ck off" and gives it a little kick back towards neutral :S

joeyjoejoejuniorshabadoo Grand Master

joeyjoejoejuniorshabadoo

Posted
Posted

i've had my car for 4 years now... the car is still daily'd and makes 300rwkw on the stock gearbox with a c's short shifter to really make it stressed

i have always treated the box like shit.... smash every gear change when i drive hard,(i do heel-toe on down's tho) flatshift when i need to keep them spinning and things like shoving it into first gear from 6k in second to get round cones. oil was never changed.

when i killed clutch this year we looked inside the box and it's still perfect. filled it with motul oil and it crunches 4th a tiny bit now.... but meh... i'll throw some shockproof in there when i get round to it...

moral of the story? gearboxes are replacable and in the scheme of things not that expensive... RB25 boxes are great from the factory and you shouldn't let a cheap, replacable part let you enjoy your car any less....

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