Do Double Clutch Downshifts Increase Synchro Wear

[JSRT4]

Just curious if double clutching on downshifts increases wear on synchros. My question relates to typical synchromesh manual automobile trannies. I know technically you don't need to double clutch downshifts on automobile synchromesh trannies, but I find that it feels much smoother when you do it. Maybe it's just a habit left over from my truck driving days. Do you think it affects synchro wear at all - for better or worse ?. thanks for any replies.

 

[moribundman]

Double clutching will reduce wear on synchros, but with so little wear already, I don't believe it to be a requisite procedure for most drivers of a modern car with a synchronized transmission. If double clutching is second nature to you, go for it. For those who want to learn double clutching, first learn heel-toe rev-matching.

 

[Spitty]

It would only wear the syncros if you do it badly. Done correctly it will help save your syncros. If care is taken in matching road speed to engine speed, it's possible to change gear smoothly without using the clutch at all!

 

[bdcardinal]

i just heel-toe depending on what shoes im wearing, if i have clumbsy boots on, then no. but if im wearing my puma trifonos like i usually do, then heel-toe all the way.

no real advantage to double clutch on my car at least.

 

[moribundman]

Originally Posted By: Spitty
Done correctly it will help save your syncros.


Put all the fallen out synchros under my pillow at night.

 

[JSRT4]

thanks for the replies, yeah I guess it is kinda second nature to me, and I like the way the shifter just falls into place on a properly done double clutch downshift, the shifter almost gets sucked out of your hands. mmm,mmm, good

 

[moribundman]

Keep doing what you're doing, because you've got the art of shifting down pat.

 

[mechtech2]

Double clutching on downshifts is better for the synchros if you do it right. If it is smooth, you probably are.
It doubles the wear on the clutch actuating parts, though.
Rev matching will do the same thing as double clutching in a synchro trans, and makes things simpler.

 

[sprintman]

I double clutch on everything but on the BMW I just bought it's nearly impossible, the accelerator is way to heavy.

 

[JSRT4]

Originally Posted By: sprintman
I double clutch on everything but on the BMW I just bought it's nearly impossible, the accelerator is way to heavy.


yeah in those circumstances you usually have to really stab the accelerator to get the revs up high enough and quick enough, otherwise it doesn't work properly. I know the feeling.

Thanks for all of the replies on this subject.

 

[JohnBrowning]

HAHAHA My Dad taught me heel-toe, rev-matching, and neat stuiff like threshold brakeing and how to steer the rear end with throtle etc..... Nothing like a raceing fan teaching you to drive. The autobahn was a great place to learn and practice driveing. When I came back to the United States all Mom did was yell at me to slow down and take my left hand blinker off!!!!!LOL It did not help that I my family is a two vechile type family either truck based vechile or low slung sports car's so I had temptation calling my name every time I got behind the wheel!!!LOL

 

[Steve S]

Double clutching " push in the clutch rev or drop rpm as needed upshift or downshift release the clutch" is to allow the gears "speeds" to be matched in a non syncro trans like a semi truck trans so they will not grind "will not" shift into gear. In a syncromesh trans the all the gears are always meshed " Not reverse" and the syncro assemblies lock the free spinning gears . Now when upshifting the engine rpms drop and when downshifting the engines rpms rise so when blipping the throttle when down shifting you are matching the engines rpms to the trans rpm and saving the clutch

 

[parimento1]

Double clutching saves the synchros from wear (if you double clutch you are not making use of the synchros because you are doing the job that the synchronizers would do, thereby saving the synchros)

 

[sprintman]

All good drivers double clutch when they change down Bad drivers don't.

 

[double vanos]

In a modern synchromesh transmission, I'd like to think that proper lubricant change intervals utilizing the best lubricants would be a major factor in reducing synchro wear.

Naturally, rev matching and double clutching helps too. I rev match as much as I possiblly can - good for the trans and fun too. Cheers!

 

[aquariuscsm]

Is double clutching:

Accelerate in 1st,depress the clutch pedal,shift into neutral,release the clutch pedal,re-depress the clutch pedal,shift into 2nd?

Is that the basic principal? They discuss double clutching on Twinturbo.net all the time for people with bad synchros in their trannies to avoid gear crunch.

 

[JustinH]

It's too much nonsense for my econobox saturn ion.

I shift directly into second.

 

[JSRT4]

Originally Posted By: aquariuscsm
Is double clutching:

Accelerate in 1st,depress the clutch pedal,shift into neutral,release the clutch pedal,re-depress the clutch pedal,shift into 2nd?

Is that the basic principal? They discuss double clutching on Twinturbo.net all the time for people with bad synchros in their trannies to avoid gear crunch.


That is almost correct, but it is used mainly in downshifting situations, if you have to double clutch to upshift in a synchromesh tranny I would suggest buying a new transmission. The procedure for downshifting (say 3rd to 2nd for example) is to push clutch in and pull shifter into neutral from 3rd. Release clutch, then hit accelerator pedal and build revs up quickly (usually 3k-4k range), push in clutch again and then pull shifter into 2nd gear, release clutch with a bit of accelerator pedal to rev match. Once you get good at it, you can do the entire procedure in a fraction of a second and you know that you got it right when the shifter just falls into 2nd gear like nothing. I usually double clutch on downshifts into 2nd, not so much in higher gears. Double clutching also helps alot with down-shifting into first gear while the vehicle is moving, some cars are very notchy shifting to first when the vehicle is moving, double clutching makes it much easier.

BTW, rev matching is just applying accelerator pedal as you release the clutch, making the transition smooth by getting the rpms up a bit. If you don't rev match when releasing the clutch on a shift then the engine braking can cause a jerky motion as it wants to decelerate. Rev matching and double clutching are two different things, though often used together.

 

[MCompact]

I double-clutch downshift 100% of the time on the street to keep me in practice for HPDEs. And it doesn't matter which vehicle I'm driving- 3 Series, Mazdaspeed3, or Wrangler.

 

[JHZR2]

Originally Posted By: sprintman
I double clutch on everything but on the BMW I just bought it's nearly impossible, the accelerator is way to heavy.


The E30??!?

The way mine feels when double clutching on a downshift is pure magic! There is a slight suction on the shifter that makes me feel as if the car is guiding me.

Is your trans and all the bushings, etc. OK?

JMH