2015 auto uncommanded downshifting
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Joined: Sep 2014
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From: Muskoka ontario
2015 auto uncommanded downshifting
Just got the new machine and noticed when going down a steep hill as the car speeds up a light brake pressure is applied and the tranny starts downshifting.....conditions are; DRIVE(not manual),TOUR mode,cruise control OFF, shift paddles not touched.Any else see this with the new 8 speed auto tranny ?? tks
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I was in the Ozark mountains this past weekend and my 2015 also downshifted going down steep hills. Mine always seemed to downshift and maintain 3000 rpm under the same conditions as you described; I tried every mode except track, and the results were the same. I don't much like the downhill downshifting but I'm assuming it's some sort of safety feature; Big Brother is always looking out for us these days. But, it won't really be an issue for me, as so far it only occurs on really steep hills and there aren't any of those in my area. Hopefully, the tech-savvy forum members can tell us if this is normal behavior for the 2015 eight-speeds.
Thread Starter
Pro
Joined: Sep 2014
Posts: 701
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From: Muskoka ontario
I was in the Ozark mountains this past weekend and my 2015 also downshifted going down steep hills. Mine always seemed to downshift and maintain 3000 rpm under the same conditions as you described; I tried every mode except track, and the results were the same. I don't much like the downhill downshifting but I'm assuming it's some sort of safety feature; Big Brother is always looking out for us these days. But, it won't really be an issue for me, as so far it only occurs on really steep hills and there aren't any of those in my area. Hopefully, the tech-savvy forum members can tell us if this is normal behavior for the 2015 eight-speeds.
Safety Car
Joined: Mar 2014
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From: Kilmarnock Va
Sorry about change of subject.
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Joined: Mar 2005
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From: La Center WA
Just got the new machine and noticed when going down a steep hill as the car speeds up a light brake pressure is applied and the tranny starts downshifting.....conditions are; DRIVE(not manual),TOUR mode,cruise control OFF, shift paddles not touched.Any else see this with the new 8 speed auto tranny ?? tks
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
I was in the Ozark mountains this past weekend and my 2015 also downshifted going down steep hills. Mine always seemed to downshift and maintain 3000 rpm under the same conditions as you described; I tried every mode except track, and the results were the same. I don't much like the downhill downshifting but I'm assuming it's some sort of safety feature; Big Brother is always looking out for us these days. But, it won't really be an issue for me, as so far it only occurs on really steep hills and there aren't any of those in my area. Hopefully, the tech-savvy forum members can tell us if this is normal behavior for the 2015 eight-speeds.
Thread Starter
Pro
Joined: Sep 2014
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From: Muskoka ontario
Thread Starter
Pro
Joined: Sep 2014
Posts: 701
Likes: 179
From: Muskoka ontario
Racer
Joined: Jun 2004
Posts: 445
Likes: 32
From: Chicago IL
You Have To Train Your Transmission
There was an earlier thread about the A8 trans. In it there was a reference to a service bulletin (#14-07-30-001A - Information on Transmission Adaptive Functions) that when I went to read it downloaded to my desktop. It explains how you have to TRAIN your transmission.
"Some customers may comment on low mileage vehicles with automatic transmission that shift feel to be too firm (harsh) or may slip or flare. Customers should be advised that the transmission makes use of an adaptive function that will help to refine the shift feel while driving and improve shift quality.
Transmission Adaptive Functions
The Hydra-Matic® 8-Speed RWD transmission utilizes a line pressure control system during upshifts to compensate for new transmission build variation as well as the normal wear of transmission components. The variation experience on a new and normal wear of the apply components within the transmission over time can cause shift time (the time required to apply a clutch) to be longer or shorter than desired.
In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various pressure control (PC) solenoids to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as “adaptive learning” and it is used to ensure consistent shift feel plus increase transmission durability.
The TCM monitors the A/T input speed sensor (ISS) and the A/T output speed sensor (OSS) during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the corresponding PC solenoid signal to maintain the set shift feel. The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle."
It mentions 3-1, 2-1, and Power Downshifts.
The bulletin is two pages with a chart, so it might be worth checking out to see how to program your trans.
Hope this helps.
Sly
"Some customers may comment on low mileage vehicles with automatic transmission that shift feel to be too firm (harsh) or may slip or flare. Customers should be advised that the transmission makes use of an adaptive function that will help to refine the shift feel while driving and improve shift quality.
Transmission Adaptive Functions
The Hydra-Matic® 8-Speed RWD transmission utilizes a line pressure control system during upshifts to compensate for new transmission build variation as well as the normal wear of transmission components. The variation experience on a new and normal wear of the apply components within the transmission over time can cause shift time (the time required to apply a clutch) to be longer or shorter than desired.
In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various pressure control (PC) solenoids to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as “adaptive learning” and it is used to ensure consistent shift feel plus increase transmission durability.
The TCM monitors the A/T input speed sensor (ISS) and the A/T output speed sensor (OSS) during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the corresponding PC solenoid signal to maintain the set shift feel. The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle."
It mentions 3-1, 2-1, and Power Downshifts.
The bulletin is two pages with a chart, so it might be worth checking out to see how to program your trans.
Hope this helps.
Sly
Last edited by Groovepusher Sly; Oct 23, 2014 at 07:05 PM.
Thread Starter
Pro
Joined: Sep 2014
Posts: 701
Likes: 179
From: Muskoka ontario
There was an earlier thread about the A8 trans. In it there was a reference to a service bulletin (#14-07-30-001A - Information on Transmission Adaptive Functions) that when I went to read it downloaded to my desktop. It explains how you have to TRAIN your transmission.
"Some customers may comment on low mileage vehicles with automatic transmission that shift feel to be too firm (harsh) or may slip or flare. Customers should be advised that the transmission makes use of an adaptive function that will help to refine the shift feel while driving and improve shift quality.
Transmission Adaptive Functions
The Hydra-Matic® 8-Speed RWD transmission utilizes a line pressure control system during upshifts to compensate for new transmission build variation as well as the normal wear of transmission components. The variation experience on a new and normal wear of the apply components within the transmission over time can cause shift time (the time required to apply a clutch) to be longer or shorter than desired.
In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various pressure control (PC) solenoids to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as “adaptive learning” and it is used to ensure consistent shift feel plus increase transmission durability.
The TCM monitors the A/T input speed sensor (ISS) and the A/T output speed sensor (OSS) during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the corresponding PC solenoid signal to maintain the set shift feel. The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle."
It mentions 3-1, 2-1, and Power Downshifts.
The bulletin is two pages with a chart, so it might be worth checking out to see how to program your trans.
Hope this helps.
Sly
"Some customers may comment on low mileage vehicles with automatic transmission that shift feel to be too firm (harsh) or may slip or flare. Customers should be advised that the transmission makes use of an adaptive function that will help to refine the shift feel while driving and improve shift quality.
Transmission Adaptive Functions
The Hydra-Matic® 8-Speed RWD transmission utilizes a line pressure control system during upshifts to compensate for new transmission build variation as well as the normal wear of transmission components. The variation experience on a new and normal wear of the apply components within the transmission over time can cause shift time (the time required to apply a clutch) to be longer or shorter than desired.
In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various pressure control (PC) solenoids to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as “adaptive learning” and it is used to ensure consistent shift feel plus increase transmission durability.
The TCM monitors the A/T input speed sensor (ISS) and the A/T output speed sensor (OSS) during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the corresponding PC solenoid signal to maintain the set shift feel. The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle."
It mentions 3-1, 2-1, and Power Downshifts.
The bulletin is two pages with a chart, so it might be worth checking out to see how to program your trans.
Hope this helps.
Sly
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
There was an earlier thread about the A8 trans. In it there was a reference to a service bulletin (#14-07-30-001A - Information on Transmission Adaptive Functions) that when I went to read it downloaded to my desktop. It explains how you have to TRAIN your transmission.
"Some customers may comment on low mileage vehicles with automatic transmission that shift feel to be too firm (harsh) or may slip or flare. Customers should be advised that the transmission makes use of an adaptive function that will help to refine the shift feel while driving and improve shift quality.
Transmission Adaptive Functions
The Hydra-Matic® 8-Speed RWD transmission utilizes a line pressure control system during upshifts to compensate for new transmission build variation as well as the normal wear of transmission components. The variation experience on a new and normal wear of the apply components within the transmission over time can cause shift time (the time required to apply a clutch) to be longer or shorter than desired.
In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various pressure control (PC) solenoids to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as “adaptive learning” and it is used to ensure consistent shift feel plus increase transmission durability.
The TCM monitors the A/T input speed sensor (ISS) and the A/T output speed sensor (OSS) during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the corresponding PC solenoid signal to maintain the set shift feel. The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle."
It mentions 3-1, 2-1, and Power Downshifts.
The bulletin is two pages with a chart, so it might be worth checking out to see how to program your trans.
Hope this helps.
Sly
"Some customers may comment on low mileage vehicles with automatic transmission that shift feel to be too firm (harsh) or may slip or flare. Customers should be advised that the transmission makes use of an adaptive function that will help to refine the shift feel while driving and improve shift quality.
Transmission Adaptive Functions
The Hydra-Matic® 8-Speed RWD transmission utilizes a line pressure control system during upshifts to compensate for new transmission build variation as well as the normal wear of transmission components. The variation experience on a new and normal wear of the apply components within the transmission over time can cause shift time (the time required to apply a clutch) to be longer or shorter than desired.
In order to compensate for these changes, the transmission control module (TCM) adjusts the pressure commands to the various pressure control (PC) solenoids to maintain the originally calibrated shift timing. The automatic adjusting process is referred to as “adaptive learning” and it is used to ensure consistent shift feel plus increase transmission durability.
The TCM monitors the A/T input speed sensor (ISS) and the A/T output speed sensor (OSS) during commanded shifts to determine if a shift is occurring too fast (harsh) or too slow (soft) and adjusts the corresponding PC solenoid signal to maintain the set shift feel. The purpose of the adapt function is to automatically compensate the shift quality for the various vehicle shift control systems. The adapt function is a continuous process that will help to maintain optimal shift quality throughout the life of the vehicle."
It mentions 3-1, 2-1, and Power Downshifts.
The bulletin is two pages with a chart, so it might be worth checking out to see how to program your trans.
Hope this helps.
Sly
Pro
Joined: Oct 2005
Posts: 680
Likes: 17
From: Moulton Alabama
Cruise-In 8-9-10-12 Veteran
Yes I agree , there are cases where the downshifting works well and with a manual trans you have complete control of when to down shift and by how much. The issue I'm having is the AUTOMATIC 8 speed tranny downshifts is all the time ( cruise control off) as soon as you touch the brakes even lightly going down hill it sometimes down***** by at least 2 gears so its making the decision rather than the driver....what I discoverd this afternoon coming home was just before starting down the grade I shifted the drive selector from D to M . In "M" the instrument cluster showed I was in 7th gear and as I went down the long hill the car started gaining speed and with very light brake pressure I was able to control speed and " NO UNCOMMANDED DOWNSHIFTING as in M the shift paddles are controling. This left me the option of contiuing with braking OR using the paddles to downshift maybe one gear or two but now I'm in control of it making the decision and by how much and when.....O.K. I admit it , I must be a "control freak "
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From: Phila Suburbs 2023 C8 & 2013 650ix
but If you want to manually shift, use the paddles.
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