Double-clutching vs. powershifting

As I stated in my truck...don't care what you do in your truck. I'll gladly replace my clutch, don't have a problem in doing that. But replacing a clutch is cheaper than the alternative....my opinion.

I know the first thing any newbie wants to do is float gears...one of the reasons company trucks are worth their weight you got people you can barely shift by clutching and now they are slamming gears....excuse me "floating gears".

 

I didn't use a clutch for nine years except for several things.
Of course, starting and stopping. Also when we'd put it into gear at a stop, we'd hold the clutch down for a second before trying to put it in gear.
Next is bumps, hills, or any time you're not entirely sure you are correct in the rpm's. Clutch that sucker so you don't wind up with a bang that can break teeth, bend shafts, put metal filings in the oil and curse you for eternity.
I always took personal pride in being able to float even odd splits. I agree with Ron-Mars in that if you're doing it right, it goes right in with two fingers. If not, your speed is wrong, and you should always clutch when in doubt. After a while, you find that (at least on the flats) you rarely use the clutch, but should always be ready to abort any move instantly.

 

I see your point where noobs are concerned, howerver, floating doesn't necessarily equal "slamming". I'm willing to bet you that my floating is as smooth as your double-clutching.

 

One of my buddy's used to own his own Tractor/truck repair shop.
He had many large accounts such as FedEx and The City of Chino for example. Most of his customers asked him to show their new drivers how to use the tranny properly. He always taught them how to double-clutch first but then he would show them how to Tach shift.
In his experience, drivers who knew how to tach-shift and do so properly, cause less wear and tear on a truck and tranny. Why?????
Because those who know how to Tach-shift learned the basic rules of Listening and Feeling. Many drivers who only know how to Double-clutch "depend" on the clutch.

I knew mechanic from a major contractor who always wanted us to use the clutch even for splitting gears on a Two-speed rear axle.

Rear axles still got torn up because drivers "depended" on the clutch and not their ears and their touch.


Let's see a show of hands of those of you who "Progressive shift".........

Works better by Tach-shifting...at least in my experience.

 

I'm with ya there, Ron

 

Can someone explain why (mechanically speaking, not theory) there is a NEED to Double Clutch the the Clutch when using the clutch to shift? No one has ever explained the reason you have to double clutch. Once the Clutch pedal is pushed in the engine and transmission are operating independently so I dont see what the second clutching does for the process.

 

If you're in the properly seated position with all of the air out of your seat, on the floor with a long hood sticking out and a 60" shifter and the latest pair of lime green Tony Lama's on, you'll have to float those gears cause you'll never get your foot high enough to clutch anyways.

 

You are needing to understand the difference between [h=2]Synchronized transmission and Un-sychronized transmissions. .[/h]
While Wikipedia is not the best source try

http://en.wikipedia.org/wiki/Manual_transmission

 

I had the same question. Involved in shifting gears you have, the crankshaft of the engine, the input shaft going into the transmission and then the output shaft of the transmission, aka the drive shaft. Inside the transmission the input shaft gets meshed up with the drive shaft through a variety of gears.

The shifting inside the tranny happens when the gear ratios coupling the transmission input shaft to the driveshaft are changed. To accomplish this, the input shaft and driveshaft are de-coupled (shifted into neutral) and temporarily spin independent of each other. In a car transmission, which has syncro-mesh, that syncro-mesh works by helping to match the rotation speed of input shaft to the rotation speed of the driveshaft. so, when the gears engage with each other, they are spinning at the same speed and everything works well.

However, in a semi tranny, without syncro-mesh, once the driveshaft and input shaft have been decoupled (put in neutral) during the process of a shift, there is nothing to adjust the rotational speed of the input shaft. The other end of the input shaft is coupled to the crankshaft of the engine through the clutch assembly and if the clutch is engaged, the input shaft is literally free spinning on both ends and there is no mechanism to adjust it's rotational speed.

So, a double clutch works like this. Push in the clutch and shift into neutral. (at this point input shaft is free-wheeling) while in neutral, let out the clutch to stop the clutch from free wheeling and to match up with the rotational speed that is needed for the next gear. Push the clutch back in and then engage the input shaft together with the driveshaft so that when the clutch is let out the second time and the shift is complete.

With floating gears you simply never disengage the crankshaft from the input shaft (except for complete stops). It takes a bit of finesse to float gears, but a good double clutch is pretty cool too! I'm can't side with which is better or anything like that.

Hope my explanation helped. I was puzzled until I figured out that the input shaft ends up free wheeling if you don't have syncro-mesh.

 

Been a mechanic for 35 years, and rebuilt an uncounted number of trans, and lv gn is correct.

I would like to add; 95% should use a clutch because they can NOT float shift correctly, but we do THANK you for the work.