Auto Guys - Our ZL1 Trans ALWAYS shifts to 1st in "M" with NO TAPS

[StormWarning]

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!

Originally Posted by StormWarning

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!!

[StormWarning]

Originally Posted by StormWarning

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!

[ZEDL1]

With a 6 speed trans, auto or manual, would not 5 shift points be all that is possible?

[StormWarning]

Originally Posted by ZEDL1

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!

[Deke736]

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.

[1MtnGoat]

In "M" 2nd gear start unless I "tap" it down to first.

[rpepka]

Mine started in 1st in M mode without tapping it down to 1st

[Stephen12ZL1]

M mode with "S" on dash = starts in 1st. D mode = 2nd gear start. No taps.

[RoketRdr]

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.

[Drew P]

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.

[MEDISIN]

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!

[mikebutry]

Mine starts in whatever gear I clutch it into

[rpepka]

Originally Posted by mikebutry

Mine starts in whatever gear I clutch it into

Sheeeeet

[MEDISIN]

Originally Posted by mikebutry

Mine starts in whatever gear I clutch it into

Which does give you a better look at my tail lights