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Old 09-18-2012, 10:01 PM   #1
StormWarning
 
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Auto Guys - Our ZL1 Trans ALWAYS shifts to 1st in "M" with NO TAPS

I posted this response in another thread when someone asked me a question about our Auto Trans starting out in second gear when in “M” and NOT using the taps. Not True – our auto trans does not work that way – it Always downshifts into first gear when stopping with no taps when in “M”.

Here are my posts and videos – take a ride with us and count the shifts. Maybe we can all agree and settle this issue once and for all. Here goes! Our shift-counting video is in the next post!

Quote:
Originally Posted by StormWarning View Post
Ah jeez, I really hate to open this can of worms again! But what the hay. Here is my take on how the Auto works regarding "M", not "D".

I've heard all about the 2nd gear starts, and I've found that to be TRUE in "D" under "normal" driving (except for first start). When it "D", mine ALWAYS takes off in second. And yeah I'm one kinda those guys - I count the shifts!


OK - "M" position, also called "Sport". I was able to find a quiet 1/2 mile road that has a full retaining wall running by the curb. This helps to amplify the exhaust and hear the shifts. Now, EVERY TIME I idle down in "M" to the stop sign (NO TAPS touched), I begin to count the shifts. I can feel them and hear them. My throttle pressure is normal - no hotfoot. It takes me a little over a 1/4 mile to reach about 52 MPH the way I accelerate. And right about 53, it shifts into SIXTH GEAR -every time!


It makes sense I think. As indicated in the Owners Manual, "D" is for gas mileage kinda, and "M" is for Sport. You would want a little more guts in the "M" Sport mode, so it makes seems sense that the trans will always shift to 1st gear in "M" all the time, (taps or no taps) for a "Sport-ier" start.


From the Owners Manual:
"When coasting to a stop in Tap Shift
Mode, the V8 transmission will
automatically downshift to
2 (Second) gear. A 1 (First) gear
start can be selected using the Tap
Shift controls on V8 models."

Right - this is what mine does if I'm in "M" and have been screwing around with the Taps! But it drops to first when I stop if I haven't used the taps!

I tried to make a video a day or two ago along that road and it didn't come out well. How about this -- I'll try and make another one this afternoon and then we'll ALL go for a ride and count the shifts!!


Last edited by StormWarning; 09-18-2012 at 10:14 PM.
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Old 09-18-2012, 10:03 PM   #2
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Quote:
Originally Posted by StormWarning View Post

I tried to make a video a day or two ago along that road and it didn't come out well. How about this -- I'll try and make another one this afternoon and then we'll ALL go for a ride and count the shifts!!

OK Auto trans fans, here we go!
I asked my wife and Assistant Crew Chief Jungle Pat to take the wheel of "Crystal" as we try and document a six-shift sequence while accelerating after coasting to a stop in "M" and not using the Taps. Our ZL1 always shifts down to First under this scenario and up-shifts five (5) times. Here is what we did:

Drove around for a while with the trans in "M"
Never once touched the Taps
Jungle Pat decelerated normally to a stop sign - didn't touch a thing
She accelerated normally and the car up-shifted five(5) times ending in sixth (6th) gear.

At least that's the way ours works! Count the shifts and watch the tach as we accelerate. I sure hope this helps shed some light on this topic! Maybe one day we can all figure it out!

Enjoy the ride!


P.S. You can actually feel the different gear ratios when taking off in "M" (4.03 1st gear ratio) vs "D" (2.36 2nd gear ratio).
P.P.S. I bet there's a whole lot of ZL1 shift-counting going on tonight !







Let the games begin!


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Old 09-18-2012, 10:07 PM   #3
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With a 6 speed trans, auto or manual, would not 5 shift points be all that is possible?
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Old 09-18-2012, 10:11 PM   #4
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Originally Posted by ZEDL1 View Post
With a 6 speed trans, auto or manual, would not 5 shift points be all that is possible?

Yes - our trans UPSHIFTS Five times ending in Sixth (6) gear!
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Old 09-18-2012, 11:16 PM   #5
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Mine starts in second. I'm not going to make a video to prove it, but if I want to start out in first I have to downshift it manually.
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Old 09-19-2012, 05:12 AM   #6
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In "M" 2nd gear start unless I "tap" it down to first.
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Old 09-19-2012, 05:48 AM   #7
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Mine started in 1st in M mode without tapping it down to 1st
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Old 09-19-2012, 05:53 AM   #8
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M mode with "S" on dash = starts in 1st. D mode = 2nd gear start. No taps.
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Old 09-19-2012, 05:57 AM   #9
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This is very odd. Seems that some are downshifting into 1st and some aren't. Both methods of operation have been proven by different cars and owners so it looks like GM did some playing around with the TCM on some cars.
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Old 09-19-2012, 06:43 AM   #10
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I have noticed that even when driving in M (S on dash read-out), if you are not driving aggressively, the car begins to shift as though it is in D. This might explain the difference, just guessing. Btw - my car starts in 1st when initially placed into M.
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Old 09-19-2012, 06:53 AM   #11
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Sounds the same as the CTS-V auto. "D" will start in first gear when shifted from "P", "R", or "N" only. After that it starts in second gear for the remainder of your trip. "S" will start in first each and every time. Once you touch the tap-shift, you hold a gear to redline but it will downshift for you if the RPM's fall to low. In this situation, it only downshifts to second when you come to a stop. Quirky but predictable!
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Old 09-19-2012, 06:55 AM   #12
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Mine starts in whatever gear I clutch it into
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Old 09-19-2012, 06:59 AM   #13
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Quote:
Originally Posted by mikebutry View Post
Mine starts in whatever gear I clutch it into
Sheeeeet
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Old 09-19-2012, 07:00 AM   #14
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Quote:
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Mine starts in whatever gear I clutch it into
Which does give you a better look at my tail lights
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Old 09-19-2012, 07:27 AM   #15
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Quote:
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Which does give you a better look at my tail lights
Yeah? Real world, the fastest stock Z we've seen from an owner was manual (number1gmfan)

Edit - sike, I see you have a cts-v. Which, for whatever reason, is faster.
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Old 09-19-2012, 07:45 AM   #16
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Storm Warning, Do you think it could be starting in second and the last shift which you think is a 5th to 6th shift is actually 6th and then the torque converter locking up?
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Old 09-19-2012, 09:02 AM   #17
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A video showing both the tach and the speedometer should clear up any question about the possibility of the torque converter locking up and causing some confusion. MPH @ RPM can be resolved down to transmission gear ratio as long as you know what the tire revs/mile are and the differential gear ratio.

Might want to check at a couple different speeds without allowing an upshift just to check consistency.


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Old 09-19-2012, 09:37 AM   #18
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I have confirmed second gear starts in Drive and Paddle mode
Sport mode (shift Pattern A) starts in 1st

These are Screen shots of my tuning software from a 2012 ZL-1 Auto.

In the paddle mode picture I have changed the values from 0 to 8.5 mph to promote a 2-1 down shift when coming to a stop.

Shift pattern A would be Sport Mode
Shift pattern B would be Drive Mode
Paddle mode is obvious.
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Old 09-19-2012, 09:41 AM   #19
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Quote:
Originally Posted by StormWarning View Post

OK Auto trans fans, here we go!
I asked my wife and Assistant Crew Chief Jungle Pat to take the wheel of "Crystal" as we try and document a six-shift sequence while accelerating after coasting to a stop in "M" and not using the Taps. Our ZL1 always shifts down to First under this scenario and up-shifts five (5) times. Here is what we did:

Drove around for a while with the trans in "M"
Never once touched the Taps
Jungle Pat decelerated normally to a stop sign - didn't touch a thing
She accelerated normally and the car up-shifted five(5) times ending in sixth (6th) gear.

At least that's the way ours works! Count the shifts and watch the tach as we accelerate. I sure hope this helps shed some light on this topic! Maybe one day we can all figure it out!

Enjoy the ride!


P.S. You can actually feel the different gear ratios when taking off in "M" (4.03 1st gear ratio) vs "D" (2.36 2nd gear ratio).
P.P.S. I bet there's a whole lot of ZL1 shift-counting going on tonight !







Let the games begin!


One of those shifts is the torque converter locking
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Old 09-19-2012, 10:12 AM   #20
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I think that last one was torque converter but could not tell 100%. the last step with these newer auto's is usually a 3-500rpm drop that is the coverter locking up not another gear.

an easier way to test would be start rolling then tap down and see if you gain RPMS. much less counting.
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Old 09-19-2012, 10:16 AM   #21
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I noticed if you shift down to manual without touching the paddles it will start in second but once I touch the paddles it will go down to first. There seems to be two modes in the manual shift.
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Old 09-19-2012, 10:28 AM   #22
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Shifting to manual automatically downshifts one gear. In 4th... goes to 3rd....

So if your sitting still, it's actually in 2nd. And you select - manual mode. It does it's one gear downshift to 1st. So for that first start, it will be in 1st.

But, the normal start gear is 2nd after a coast down and not touching anything. You can start in 1st by paddling down, or it will be in 1st for that 1st start after moving the shifter to manual.

The 2nd gear start thing, and the one gear downshift when going to manual mode are in the owner's manual.
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Old 09-19-2012, 10:30 AM   #23
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Can't someone confirm what gear it's starting out in by RPM vs MPH factoring in the gear ratios? Would'nt that eliminate all doubt?
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Old 09-19-2012, 10:37 AM   #24
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The owner's manual says it starts in 2nd. For a 1st gear start, it says to paddle shift down one.

The one time I can think that it might automatically do a 1st gear start is if you moved the shifter to manual mode while it was in 2nd... because of the one gear downshift when going to manual mode. Maybe? Just my thinking.

One could test this by go to manual mode while in 3rd or 4th, go into tap shift mode. Roll to a stop, letting it downshift by itself. Easily roll forward 1 or 2 mph, and do a tap shift down. Did it go down a gear? I'll guess that it did.

Then do the same take off, but put the car in manual mode when sitting still. This will show if that first take off after going to manual mode will cause a one time 1st gear start.

Or, have a friend with a scanner watch the shift data while experimenting. Probably the most accurate.
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Old 09-19-2012, 11:06 AM   #25
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Quote:
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Can't someone confirm what gear it's starting out in by RPM vs MPH factoring in the gear ratios? Would'nt that eliminate all doubt?
Did anyone Read my post
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