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Discussion Starter #1
upon normal acceleration, I dont notice anything, however, when I punch 1st gear, and go for a "race situation" 1-2 shift....i get a light grind upon entering 2nd gear. It feels like the gear is empty when I jam it in there (best way i can describe it) yet with a slight grinding. It goes into gear fine tho. did i screw up my synchro? Please let me know what yall think.
 

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See you in the funny papers
04 CTS-V, 05 STS, 07 SRX- All sold :(
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Problem #1

"When I jam it in there."

Synchros don't work instantaneously. Shift quickly, but don't jam. Your RPMS need to time to drop anyway, so not only will your transmission last longer, but you'll be faster as well.

That's the truth.
 

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2005 CTS-V
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8,363 Posts
Problem #1

"When I jam it in there."

Synchros don't work instantaneously. Shift quickly, but don't jam. Your RPMS need to time to drop anyway, so not only will your transmission last longer, but you'll be faster as well.

That's the truth.
I am little confused by part of this answer as it would apply to 1-2 shift in a "racing situation." Specifically the phrase "your RPMS need...time to drop anyway." Where I come from, during a racing situation the accelerator pedal remains against the floor while the clutch is used during the shift and the RPMs do not drop they rise. In fact, the trick is to complete the shift before you overev the engine. This, of course, no way to drive all the time.
 

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04 CTS-V, 05 STS, 07 SRX- All sold :(
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Where I come from, during a racing situation the accelerator pedal remains against the floor while the clutch is used during the shift and the RPMs do not drop they rise. In fact, the trick is to complete the shift before you overev the engine.
They must replace transmissions and pushrods a lot where you come from.

If you run your engine to its HP peak before shifting (as you should), there will not be enough time to perform a "speed shift" as you described before over-revving the engine. If you do accomplish this feat, you are doing so by letting the clutch out before the next gear is fully engaged, thus putting undue strain on the shift forks and synchros.
 

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They must replace transmissions and pushrods a lot where you come from.

If you run your engine to its HP peak before shifting (as you should), there will not be enough time to perform a "speed shift" as you described before over-revving the engine. If you do accomplish this feat, you are doing so by letting the clutch out before the next gear is fully engaged, thus putting undue strain on the shift forks and synchros.
Odd. I have done and seen a lot of racing and have never seen it done any other way. (With the possible exception of some endurance racing) Properly done the motion of the clutch pedal and the shifter start and end at the same time. In fact, it is my understanding that rev limiters were first invented to reduce blown engines in racing because of power shifting.
 

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See you in the funny papers
04 CTS-V, 05 STS, 07 SRX- All sold :(
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Crashboxes were invented for speed shifting- rev limiters are for mistakes.

Since the HP peak in 1st gear of an LS6 CTS-V is at 6,700rpms (past the 6,600 limiter) you should still be accelerating in gear until just before the rev limiter if you want to get the most power down, so it's impossible to speed shift without hitting the limiter. If you're pulling it off, it means you're shifting way too early and not taking advantage of the best part of your powerband. When you hit the limiter, there's a hard fuel cutoff that causes the car to buck pretty hard, defeating the goal of smooth, constant acceleration. Also, it's nearly impossible to grab second smoothly coming off the limiter without bogging the engine while it recovers from the fuel cut.

Try shifting quickly but smoothly and you might be surprised at the results.
 

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If I shift too fast from 1st to 2nd I find I pretty much spin through alot of 2nd gear and end up quickly having to shift into 3rd...essentially wasting alot of 2nd gear's ratio advantage.


I, too, sometimes have felt that slight grinding when shifting hard into 2nd. I've always thought it happens after a long day at work and I'm just starting to let the clutch out a millisecond too soon.
 

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My transmission did not shift smooth from 1 to 2. It felt like I engaged the gear, so I leave the clutch out and it grinds. I think what is happening is you engage the synco but not the gear. I put in Royal Purple and the shifiting is 1000 percent better. Much smoother shifts.
 

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Crashboxes were invented for speed shifting- rev limiters are for mistakes.

Since the HP peak in 1st gear of an LS6 CTS-V is at 6,700rpms (past the 6,600 limiter) you should still be accelerating in gear until just before the rev limiter if you want to get the most power down, so it's impossible to speed shift without hitting the limiter. If you're pulling it off, it means you're shifting way too early and not taking advantage of the best part of your powerband. When you hit the limiter, there's a hard fuel cutoff that causes the car to buck pretty hard, defeating the goal of smooth, constant acceleration. Also, it's nearly impossible to grab second smoothly coming off the limiter without bogging the engine while it recovers from the fuel cut.

Try shifting quickly but smoothly and you might be surprised at the results.
I think the differences in what we are saying may be subtle. First, I am not recommending hitting the rev limter, but I do not think shifting at say 6,350-6,400 is NOT giving up all that much in terms of the useful powerband. Second, I am NOT suggesting that everyone power shift all the time because the gain over a qucik shift is small compared to the effort required. But, I do maintain that in a full race context, power-shifting is used more often than not. The attached link, under "Shifting Up While Accelerating" seems to give a fair characterization of what I am trying to say.



http://www.waycoolinc.com/z3/essentials/fixit/heeltoe/shifting.htm
 

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04 CTS-V, 05 STS, 07 SRX- All sold :(
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Interesting read. From the section on Speed Shifting:

"Generally speaking, a really well executed light-touch shift can be done quicker than most people can power-shift. It certainly is friendlier to the car."
 

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Interesting read. From the section on Speed Shifting:

"Generally speaking, a really well executed light-touch shift can be done quicker than most people can power-shift. It certainly is friendlier to the car."
Yep, thats what it says. And just for the record, I have only power shifted my V one time. That was in an unexpected drag race with a Trans Am. In that case, adrenalin and muscle memory took over and I power shifted from 1-2 and 2-3 before running out of real estate (ahead of said Trans Am).
 

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I think speed shifting has its time and place, but this car isn't one of them. There's too many linkages between us and the gearbox, so it's impossible to pull off an effective speed shift without shifting too soon or slamming the limiter, both of which are death in a drag race.

Give me a Miata (I know, not the best drag weapon- but it has a great gearbox) and I might agree. The throw lever goes straight into the transmission, so shifts are quick and instantly engage the gear, as opposed to the CTS-V which has to go "down, forward, down, forward" before the gear actually changes.
 

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You also should remember that a rev limiter is not a cureall for protecting your engine, infact it can give you a false security and cause more damage, they are ment more for top end speeds. You need to find the sweet spot, not the top of the rpm range.

I sure wish I had a manual tranny and rear wheel drive in my Seville.

I let my boy drive the Seville and he likes the power so much, he is always asking if he can nail it, but with front wheel drive and the wheel spin on shifts to second, it scares me to turn him loose as you really never know what the front end is gonna do. When he races cars and karts, he is used to drifting the car. Not so with front wheel drive.

Dan
 

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I made a quick diagram that explains why our shifters feel so loose and take longer to shift. This should give you a better idea why speed shifting won't work in this car- if you yank the shifter, you're going to create flex at the joints in our linkage, causing rough, poor or delayed gear engagement.
 

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I also believe the rev limiter in theses car is a fuel cutoff.
Which is bad if you are running N2O or some sort of F.I. without a FPSS.
Lean up that high is bad. Hell lean without that stuff is kinda yucky too.

At anyrate I have had four seperate cars with T-56s. If you are breaking it, or not picking up time in the 1/4 you aren't power shifting it right. :D
In the WS6 I have red line synthetic, shifts nice and smooth. No griding and plenty of sub 12.50 1/4 mile passes. I think my McCleod twin disk helps alot too.
 

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I made a quick diagram that explains why our shifters feel so loose and take longer to shift. This should give you a better idea why speed shifting won't work in this car- if you yank the shifter, you're going to create flex at the joints in our linkage, causing rough, poor or delayed gear engagement.
Well, I learned to power shift using a three-speed on the column. The V, while not the easiest, is hardly the worst to power-shift.
 
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