I always wanted to know what Double Clutching was and is it good for your tranny?

 

Did you watch Fast and the Furious last week on ABC or something? Nah, just playing.

Double clutching is when you downshift by taking the car out of gear, putting it in neutral, then letting off the clutch, rev match to a higher RPM, put the clutch back in, and shift into the lower gear. It's much harder to do then just simple rev matching, but it used to be necessary in transmissions without syncros. Nowadays, you don't need to worry about it too much, most people will say all you need to do is rev match in order to get your car in the right RPM for the lower gear you are about to shift into. However, people with bad syncros may still have to double clutch in order to get into a lower gear without grinding. Hope that helps, and don't try this at home...

 

thx man that really cleared things up for me

 

I still double clutch if I have a problem w/ my tranny.
i.e to avoid grinds.

 

Yeah, if you have tranny problems or drive an 18-wheeler, odds are you may want to double clutch. I have also heard people say that it is slightly harmful to the syncros to simply rev match, rather than double clutch.

I guess their argument is that when you double clutch, because you put the car in neutral and let out the clutch, you are in effect 'releasing the previous gear's syncro' but if you just put in the clutch only and shift to a lower gear, the syncro is still spinning from the previous gear and this can lead to problems. I tend to think that the syncro's job is to spin, and catch the new gear up in speed to the old gear, so why would they design a transmission with this part if they didn't want us to use it? Who knows, it's one of those mysteries of life I guess. If anyone knows the answer, feel free to share it.

 

I know this might be a stupid question but what are syncros?

 

That is the definition. There are a lot of myths out there about double clutching. Sometimes I do it when I do not want the car to jerk when I downshift. I do not believe it is bad for the transmission.

 

While we are explaining everything...what is rev matching?

might as well get it all out in one onformative thread

 

Rev matching is when you rev to the rpm level so that the car wont jump.

 

when you bring up the rpm is your foot on the clutch?

 

no, you rev it up then put it in gear. I have a friend that is real good at that

 

Yes, Rev matching is when you put the clutch in, take the car out of gear, shift to the lower gear and when you are releasing the clutch, you blip the throttle enough to match the RPMs that will result from the lower gear. So, if you are going 80 in 5th, at 4000 RPMs, and you want to shift to 4th, you need to rev your motor to around 5000 RPMs when you are releasing the clutch.

Syncros are what make this rev matching possible. Syncronizers are spinning parts with teeth on a transmission. There are separate syncros that handle different gears, for example, 1st gear does not have a syncro, and neither does reverse. So then there are different syncro rings for each gear: 2-5. Now, when you are in 3rd and want to shift into 2nd, the 3rd gear syncro will move down and hook into the 2nd gear syncro with these little teeth. In effect 'catching the gear up' to the previous gear, before disengaging. On an older tranny, there was no syncro to catch you up, hence the need for double clutching.

 

i do not think that is the proper definition. I hate to say this but search under rev matching. I found a bunch of good threads

https://honda-tech.com/zerothread?id=445670

this is what I found (dont know if it is right)

double clutch=
use the clutch to take the car out of gear
car in neutral
rev to the right RPM
use the clutch to downshift to a lower gear

You step on the clutch twice hence the term DOUBLE clutching

rev matching

step on the clutch
put the car in neutral
(still on the clutch) rev the car to appropriate rpm
select lower gear
release the clutch

Thats just what I read. Honestly I am not sure anymore

 

Both of those are right for definitions, if you read my posts, they are the same processes listed there. You might note that in rev matching and double clutching, you are only in neutral for a split second. However, when rev matching, you don't take your foot off of the clutch when you are shifting from the gear into neutral and then into the next gear.

Also, you do have your foot on the clutch when rev matching, you let off when you have caught the RPMs up to the proper spot. If it's smooth and you don't see your tach fall, odds are you did it right.

 

I'm going to have to agree with BlackSage on this one. I always rev-match my car when downshifting, I find that it goes into gear much easier. I haven't tried double clutching and have yet to see anyone else do it though, sounds like something you gotta be really good at to do quickly.

I've also heard "double clutching" used in reference to punching the clutched pedal in if you bog while drag racing or anything similar. It throws the revs up.

 

Can't you heel-toe when you are double clutching for turns?

 

lol you guys remember when TFAF first came out? There was like 20 million posts about "whats double clutching?"

 

Yes, you could heel-toe for turns when double clutching, but why would you want to? I would prefer to rev match while heel toeing, I don't like putting all that extra stress on my ankle

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 631 Teggy &raquo;</TD></TR><TR><TD CLASS="quote">lol you guys remember when TFAF first came out? There was like 20 million posts about "whats double clutching?"</TD></TR></TABLE>

And damn ABC for bringing back F&F! Can't it just die already.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by purplegsr &raquo;</TD></TR><TR><TD CLASS="quote">Syncros are what make this rev matching possible. Syncronizers are spinning parts with teeth on a transmission. There are separate syncros that handle different gears, for example, 1st gear does not have a syncro, and neither does reverse. So then there are different syncro rings for each gear: 2-5. Now, when you are in 3rd and want to shift into 2nd, the 3rd gear syncro will move down and hook into the 2nd gear syncro with these little teeth. In effect 'catching the gear up' to the previous gear, before disengaging. On an older tranny, there was no syncro to catch you up, hence the need for double clutching.</TD></TR></TABLE>

How do the synchros work when you shift from let's say, 4th to 2nd? Does this cause any damage? Or do they still fit together?

 

LOL, just playin.

 

I believe a 2nd to 4th shift wouldn't be that great for your syncros, unless you were able to disengage the syncros by doing a clutch, neutral, clutch (double clutch) shift. Rev matching will still work, it just might wear your syncros more if you do it a lot. I haven't done a 5th to 3rd or 4th to 2nd shift in a long time, I just cycle through the gears - it doesn't take that long.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by purplegsr &raquo;</TD></TR><TR><TD CLASS="quote">I haven't done a 5th to 3rd or 4th to 2nd shift in a long time, I just cycle through the gears - it doesn't take that long.</TD></TR></TABLE>

Well... it's not too common, just living out here in Vegas people drive like sh*t and love to stop short for no reason. That or wait until last minute to hit the brakes. w/out ABS... downshifting is the answer...

 

It shouldn't be a big problem if you have to do an occasional 4th to 2nd or 5th to 3rd downshift. If you have time, double clutching will actually reduce the wear on your syncros. But if you don't have time or don't feel you can do it safely, rev matching and simultaneously braking when you downshift using heel-toeing should be fine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by purplegsr &raquo;</TD></TR><TR><TD CLASS="quote">Yes, you could heel-toe for turns when double clutching, but why would you want to? I would prefer to rev match while heel toeing, I don't like putting all that extra stress on my ankle </TD></TR></TABLE>

dont you think heel toe while double clutching at the same time might be a tad difficult when you are doing that quickly before a turn?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by benno &raquo;</TD></TR><TR><TD CLASS="quote">

dont you think heel toe while double clutching at the same time might be a tad difficult when you are doing that quickly before a turn?</TD></TR></TABLE>
It is at first. That's the whole point of heel-toe. You use the toe of your right foot to hold the brakes, and the heel of your right foot to hit the throttle for your double clutching. It takes lots of practice.