A8 Question
Thread Starter
Instructor
Joined: Oct 2011
Posts: 180
Likes: 41
From: Morristown Tennessee
A8 Question
My 2016 Z51 A8 slips a little going into fifth gear in a mild to moderate acceleration . The car has 2600 miles on it and has done this since new. Anyone have an idea what it takes to fix this ?
Drifting
Joined: May 2012
Posts: 1,615
Likes: 182
From: South Dennis MA
Wow, I have not experienced that with my 2016 Z51, A8. 1890 miles.
Last edited by capecodvette; Aug 12, 2016 at 08:47 AM.
Safety Car
Joined: Aug 2012
Posts: 3,960
Likes: 1,106
In mild to moderate acceleration torque converter lockup occurs shortly after this shift so are you sure what you see as slippage isn't the shift followed shortly by the torque converter mechanical clutch locking?
If there is actual slippage in the clutch packs the transmission will first try to adapt by increasing clutch pack apply pressure which will be remembered for future events and if that doesn't prevent slippage a DTC will be set illuminating the CEL. The 8L90, like other modern GM automatics, monitors rotational speed at multiple points in the transmission and if the shaft speeds aren't as they should be it will enter a protective limp mode and the CEL will be illuminated.
If there is actual slippage in the clutch packs the transmission will first try to adapt by increasing clutch pack apply pressure which will be remembered for future events and if that doesn't prevent slippage a DTC will be set illuminating the CEL. The 8L90, like other modern GM automatics, monitors rotational speed at multiple points in the transmission and if the shaft speeds aren't as they should be it will enter a protective limp mode and the CEL will be illuminated.
Last edited by NSC5; Aug 12, 2016 at 09:09 AM.
Le Mans Master
Joined: Sep 2012
Posts: 7,146
Likes: 1,940
From: Hagerstown MD
St. Jude Donor '15-'16,'18
Try taking your car out for a "spirited" drive in M mode using the paddles to up and down shift at moderate RPMs. This seems to have greatly helped my tranny shift firmer and quicker. You can also get a copy of the drive "learning" procedure and perform it as well. I did this as well. It takes about 45-60 minutes of driving on back roads with little traffic as it does involve quite a bit of speeding up and slowing down.
Drifting
Joined: May 2003
Posts: 1,755
Likes: 97
From: Sandy Utah
My car has done this since new. NO other problems with the trans. I wonder if my driving habits have not caused this. When I leave my subdivision, I always seem to get to the 4 to 5 shift just as I reach the speed limit and therefore relax the throttle input just as it shifts (it also goes into V4 mode at the same time) so, am thinking that my trans has learned to sliiiide into 5th. Is this possible?
Melting Slicks
Joined: May 2001
Posts: 2,596
Likes: 120
From: East Tennessee
The converter will be unlocked at lower speed in higher gears and at low throttle it will feel like its slipping. If there was a problem, since there is an input speed sensor and output speed sensor, if a clutch pack was slipping you would certainly see a check engine light. If the trans clutches were slipping that bad they wouldnt last long. But the PWM controlled torque converter clutch is meant to slip at certain rpm/throttle levels.
At higher rpm/throttle you shouldnt feel it.
At higher rpm/throttle you shouldnt feel it.
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Pro
Joined: Apr 2011
Posts: 512
Likes: 158
From: Augusta Maine
It's the 3c clutch disengagement. It happens in the 2-3 shift and the 4-5 shift because both of those shifts start with a 3c clutch disengagement.
It's called a soft shift. The time between the disengagement and the engagement in the next gear is a little longer resulting in a slight rise in RPM during shifts. Feels like a small surge when it engages the next gear.
Under a little harder acceleration it shifts faster and this does not occur. IME it usually happens around 2200-2400 RPM. Most noticeable with "around town driving".
It is considered normal. In a lower powered vehicle you wouldn't feel the surge and would just be a soft shift. AFAIK it is not converter related.
It's called a soft shift. The time between the disengagement and the engagement in the next gear is a little longer resulting in a slight rise in RPM during shifts. Feels like a small surge when it engages the next gear.
Under a little harder acceleration it shifts faster and this does not occur. IME it usually happens around 2200-2400 RPM. Most noticeable with "around town driving".
It is considered normal. In a lower powered vehicle you wouldn't feel the surge and would just be a soft shift. AFAIK it is not converter related.
Last edited by springer-; Aug 12, 2016 at 02:47 PM.
Melting Slicks
Joined: May 2001
Posts: 2,596
Likes: 120
From: East Tennessee
It's the 3c clutch disengagement. It happens in the 2-3 shift and the 4-5 shift because both of those shifts start with a 3c clutch disengagement.
It's called a soft shift. The time between the disengagement and the engagement in the next gear is a little longer resulting in a slight rise in RPM during shifts. Feels like a small surge when it engages the next gear.
Under a little harder acceleration it shifts faster and this does not occur. IME it usually happens around 2200-2400 RPM. Most noticeable with "around town driving".
It is considered normal. In a lower powered vehicle you wouldn't feel the surge and would just be a soft shift. AFAIK it is not converter related.
It's called a soft shift. The time between the disengagement and the engagement in the next gear is a little longer resulting in a slight rise in RPM during shifts. Feels like a small surge when it engages the next gear.
Under a little harder acceleration it shifts faster and this does not occur. IME it usually happens around 2200-2400 RPM. Most noticeable with "around town driving".
It is considered normal. In a lower powered vehicle you wouldn't feel the surge and would just be a soft shift. AFAIK it is not converter related.
I have felt the medium throttle 4-5 slip and it can drag on pretty long, hard to believe they would purposely slip the clutches that long but anything is possible I guess. Anything over 1/2 throttle and higher RPM there is no slip felt so I was never that concerned about. It has acted the same way since day 1.
Le Mans Master
Joined: Jan 2006
Posts: 6,800
Likes: 2,653
From: Down south in Dixie
Volfan, I took mine out for a run yesterday. If I'm on the same page as you, that will be the torque converter locking up in fifth gear. Mine did the same thing you described. I only felt it at slower acceleration, and lower rpm levels. Mostly in town driving. I think you're OK my friend.
Thread Starter
Instructor
Joined: Oct 2011
Posts: 180
Likes: 41
From: Morristown Tennessee
On my way to taking it to the dealer yesterday I noticed this while only in sport mode. I also tried it in manual and felt nothing ,but in the 55 mile trip I hardly had a chance to get on it for the traffic. We'll see what the pros say I hope it's my imagination ! Thanks for all the responses !!!