Noob manual questions

[MightyMouseTech]

You are assuming the syncros are the same on each gear, which they are not. This is also why they use double syncros on 1st and 2nd.

Some syncos are also on the input shaft and some are on the output shaft, and the gears they are stopping are also different weights, so that makes a difference in how quickly they can stop the gear. There are a lot of variables.

[five_timer]

Originally Posted by MightyMouseTech

skipping gears IS harder on the syncros. There will be a larger RPM difference for the shift. We had a service bulletin a couple years ago about worn syncros on Honda/Acura 6 MT's. We are supposed to go for a roadtest with the customer, and if they do skip gear changes, we are supposed to decline the repair under warranty and inform them never to skip gears.

Yeah, this makes no sense. Higher gears create progressively less torque load and engine braking, so going higher sooner is kinder. That's what autos and high efficiency programs (like in the Corvette) do. And when decellerating, as long as you slow sufficiently for a low gear, you'll reduce the number of engine-braking engagements. In general, less shifting means less wear. How is that not obvious?

[Solo_M_Tech]

Originally Posted by five_timer

Yeah, this makes no sense. Higher gears create progressively less torque load and engine braking, so going higher sooner is kinder. That's what autos and high efficiency programs (like in the Corvette) do. And when decellerating, as long as you slow sufficiently for a low gear, you'll reduce the number of engine-braking engagements. In general, less shifting means less wear. How is that not obvious?

You're not taking into account how much wear is created on the syncro's when you go from high rpm, low load, to low rpm high load. The next gear has to match the same speed as the curent gear to allow the shift. If you skip gears, you creat more stress on the syncro's because they have to do more work (read more wear and heat) to match gear speeds.

[five_timer]

Originally Posted by ApexResistance

You're not taking into account how much wear is created on the syncro's when you go from high rpm, low load, to low rpm high load. The next gear has to match the same speed as the curent gear to allow the shift. If you skip gears, you creat more stress on the syncro's because they have to do more work (read more wear and heat) to match gear speeds.

I don't see that there's any wear on the synchros simply from spinning the gears. Say you're getting onto a highway, and in order to merge with traffic, you keep it in 4th to 3500 rpm. Now you can either shift into 5th at 1800 rpm (followed almost immediately by another shift), or go right into 6th at 1200 rpm. So how are the synchros subject to any extra wear by going from 3500-1200 vs 3500-1800? And what about the synchro work you just eliminated by skipping 5th? And when you disengage 4th, the engine drops way off (unless you throttle blip), so engaging 5th creates more engine-braking than 6th.

[Solo_M_Tech]

Originally Posted by five_timer

I don't see that there's any wear on the synchros simply from spinning the gears. Say you're getting onto a highway, and in order to merge with traffic, you keep it in 4th to 3500 rpm. Now you can either shift into 5th at 1800 rpm (followed almost immediately by another shift), or go right into 6th at 1200 rpm. So how are the synchros subject to any extra wear by going from 3500-1200 vs 3500-1800? And what about the synchro work you just eliminated by skipping 5th? And when you disengage 4th, the engine drops way off (unless you throttle blip), so engaging 5th creates more engine-braking than 6th.

You are still missing the point. The syncro has to match gear speeds. That involves friction, and yes it takes more friction (heat and wear) to change the gear speeds more when skipping gears.

[five_timer]

Originally Posted by ApexResistance

You are still missing the point. The syncro has to match gear speeds. That involves friction, and yes it takes more friction (heat and wear) to change the gear speeds more when skipping gears.

So a slightly larger RPM differential will take infinitesimally more friction to match (if your mechanics are correct), but eliminating gear changes altogether will take no friction to match. And you're still not addressing the fact that shifting to an optionally higher gear at lower engagement RPM puts less load on the clutch/ transmission.

Of course this discussion is made moot, by the fact that most people who go up and down through all the gears all the time, are usually the ones who rev higher in each gear, thereby creating more synchro friction per shift than someone who shifts at more economical revs.

[jdarwin]

I'm a new owner as well - thanks for all the input.

[ShocknAwe]

If the speeds match up it will be fine. If they don't you will put extra strain on the syncros.

Simple as that. Still have to do it properly for theory to equal practice.

[amsnow440]

You could always double clutch if you're worried about synchros

And Toretto does it so it must be cool.

[JimD]

Well anybody who wants to use every gear every time in their car because they are worried about synchro wear is welcome to do so. But I plan to keep skipping and I am not worried about wear. I've been driving manuals for decades now and never have seen any signs of wear. Maybe I am increasing it some but if I don't see any evidence of that I don't see any reason to change. Lots of things are theoretically true but not of much practical significance.

[ShocknAwe]

Just being diligent about changing the fluid out max every 30k will do a lot to keep it healthy even through abuse.