rickriada

The car shudders/shakes when under light gas peddle pressure and it becomes really noticeable to me starting around 45MPH. It pretty much smooths out once I'm over 55MPH. Somehow, I think the car is "lugging" with the possible components being the A8 tranny searching for the right gear to be in at this speed level, then transferring the "shaking/shimmering" through the driveline to the rear axle. The driver's seat vibrates too as if the rear tires are out of balance. The car has just less than 5,000 miles on it and its build date is 11/15. I'm just wandering if it is my A8 as it hunts for the right gears to be in under light gas peddle acceleration pressure, actual axle issues where the transmission connects to the rear axle through the coupler or if the tires in the back are not balanced correctly or out of round, etc...

The shaking/shimmering motion on slow acceleration seems "wrong" to me to be occurring as my wife's 2016 with a 16 build date does not perform this way and it has the same equipment group and options as I do. The only difference between our two cars is one is black while the other is shark grey and their build dates are some months apart though her car has only 3,600 miles so far.

Anyone out there experiencing similar shaking on a mild acceleration when traveling in the low 40s heading up to 55 mph or so?

Is the tranny not "liking" the gentle gas peddle use since it has to hunt for the right gear (6,7 or 8?) because I'm not using enough gas peddle pressure (I'm just trying to not go to fast but keep up with those traveling in the 40-55 mph range)?

Any ideas, etc. would be greatly appreciated! Happy holidays to all out on the forum too!

Red C8 of Jax

Have you had the car since new or did you just get it and notice the shuddering?

lakemg

Sounds like you're a candidate for a new torque converter which appears to be a known potential issue for us A8 owners

rickriada

I've had the car since it was new and it started "acting like this" a couple of months ago. It did not do it when it was "younger".

Red C8 of Jax

When I was having problems with my TC the shuddering did not smooth out, it would shudder when I was in cruise control (V4) on a level road and would continue no matter how fast I was going. I felt the shudder mainly in the gas peddle. I don't think you have a TC problem but shuddering is a symptom of a bad TC. Are your RPM's going up and down when driving on a level road at a constant speed?

obxchartercaptain

Take it to "Stingray" Chevy in Plant City....they have done DOZENS of them ...

rickriada

I told one of the service writers there about this and she said that they have not heard of these symptoms hence I've reached out to the forum to see what others have experienced. The shutter doesn't seem to happen in cruise control but I need to drive it to verify that now that someone mentioned it here. I don't feel it in the gas pedal either but in the driver's seat. Gremlins in the works?

Dif

My question(s) would be, does it do this in Auto mode and when using the paddles?
I would monitor when it's in V4 and when it's in V8.
When giving it light throttle and it's in V4, is it staying in V4 when you give it more throttle ?
Note which gear it's in, speed and RPM's when it shudders.
Note if it's going to V8 when you give it more throttle but still shuttering?
The Trans would need to be staying in a rather high gear for it to lug bad enough to make the car shudder and feel it in your seat.

Just some things to consider and Good Luck

obxchartercaptain

If the car shutters....there is a problem with the TC....They are your best bet for getting it done RIGHT in the Tampa Bay area. If nothing else, go there and take the service writer out for a drive and show them the problem.

AORoads

If obx sez Stingray has seen the issue before, they have. You may be talking to someone who is a "receptionist"---I suggest you call again. This time, ask for someone like a service mgr. or someone who writes up Corvettes---believe it or not, there are Corvette-specific service writers in some dealerships. I would think Stingray would be one of them as they are one of the larger-selling, new-Corvette dealers.

rickriada

My question(s) would be, does it do this in Auto mode and when using the paddles? It acts this way in Auto mode without using the paddles.

I would monitor when it's in V4 and when it's in V8. Frankly, I have a hard time determining when it is in V4 versus V8 mode. I know I'm not using ECO mode when this happens but am usually in SPORT mode and not using the paddles to shift the car up or down.

Note which gear it's in, speed and RPM's when it shudders. It usually seems to happen when I'm in the 7th gear around 40mph and then gently accelerate towards 45-50mph while it seems to want to find the 8th gear but normally doesn't get into 8 until I'm over 55mph or so.

The Trans would need to be staying in a rather high gear for it to lug bad enough to make the car shudder and feel it in your seat. I think that it is staying in a gear that is too high (7th) when I'm doing about 40mph and it is wanting to get into 8th gear at too low a speed/rpm? Can an A8 be "tuned" to stay in lower gears until one hits 50mph or so? It may be designed to get into 8th gear as quickly as possible but to me it seems to want to get there too quickly. My A6 tranny in our C6 cars didn't ever have these symptoms....

rickriada

I talked to a service writer who took care of two factory recalls on the 16 vette when I was there. She seemed knowledgeable but did not indicate that they've had any vettes in with A8 tranny/TC issues. I'll contact them again though and seek out their "vette specialist" and tell him/her about the two that we bought from them where one doesn't do "it" (yet?) while the other does "it" now. TY!

capecodvette

No issues with our A8. Stingray Z51, A8, built 10/15, 3,200 miles.

tjs15

T/C issues don't usually show up in low mileage cars. Most have seen it begin to act up as mileage approaches 9K-10K.

joemessman

Here is the deal. You need to get it fixed. This bulletin is specifically for your car:

#PIP5337E: Shake Or Shudder On Acceleration Excessive Engine RPM Fluctuation
Between 30 And 65 MPH - (Aug 15, 2016) Subject: Shake Or Shudder On Acceleration Excessive Engine RPM Fluctuation Between 30 And 65
MPH Models:
2015 - 2016 Cadillac Escalade, Escalade ESV built prior to 11/01/15.
2015 - 2016 Chevrolet Corvette, Silverado built prior to 11/01/15.
2015 - 2016 GMC Sierra, Yukon, Yukon XL built prior to 11/01/15.
Equipped with 8L90 Automatic Transmission (RPOs M5U) and the 6.2L (RPOs L86 and LT1)
Note: This information does not apply to Silverado and Sierra models with the 5.3L (RPO L83).
Please refer to bulletin 16-NA-175 for vehicles equipped with 5.3L (RPO L83)
This PI was superseded to update labor time. Please discard PIP5337D.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI. Condition/Concern
Some customers may comment on any of the following conditions
A shake or shudder during light throttle acceleration, between 30 and 65 mph steady state driving.
Excessive engine RPM fluctuation that may be described as frequent tachometer needle movement at
constant speed when engine speed is below 1600 RPM.
A shudder feeling that may be described as driving over rumble strips or rough pavement.
It is important to note that these conditions:
Do not occur during vehicle launch from a stop.
Do not occur when the transmission is shifting gears
Do not occur when the vehicle is decelerating.
Do not occur when TCC slip speed is zero. TCC slip speed is zero in gears 2-8 when engine RPM is
greater than 1600 RPM.
2015 - 2016 Corvette: Service Bulletin: Shake Or Shudder On Accelerati... http://www.corvetteactioncenter.com/...rint-1300.html
1 of 3 9/1/2016 9:43 PM Recommendation/Instructions
Drive the vehicle while monitoring TCC slip speed.
TCC slip speed should be 10 rpm or less also note if the shudder takes place during TCC apply.
If the TCC slip speed is in the range of 10 RPM or less the condition is possibly related to engine
performance.
Monitor Active Fuel Management (AFM) to see if the engine is operating in 4 cylinder mode or
transitioning from 8 cylinder to 4 cylinder mode.
In an effort to help separate the AFM transitions from potential TCC shudder, the vehicle can be placed
in manual mode and tapped to 7th gear, this will turn off AFM.
Drive the vehicle under the same engine RPM and engine torque as the original complaint in an
attempt to duplicate the condition. Note: If the shudder is only present in 4 cylinder mode and TCC slip is 10 rpm or less deem the
shudder concern normal characteristic of AFM.
If the slip speed is beyond 10 rpm or there is shudder during TCC apply the torque converter should be
replaced following the instructions published in Service Information (SI).
Additionally the following should be performed as well during the torque converter replacement
process.
Flush the cooler lines and cooler using DT-45096 transmission oil cooling system flush and flow test
tool.
Use compressed air to remove any residual fluid from the cooler and lines.
Remove the transmission fluid pan and drain transmission fluid.
Install a new transmission filter, clean pan and magnet.
Install the transmission fluid pan and refill with new transmission fluid following the fluid fill
procedure in SI to obtain correct fluid level. Note: Only DEXRON®HP Fluid should be used. The US part number for the DEXRON®HP Fluid
is 19331925, P/N (19331926) in Canada. Important: Under certain load conditions a minor chuggle/shudder feel may be felt in the passenger
compartment due to natural engine frequencies or Active Fuel Management (AFM) transitioning from
8 cylinder to 4 cylinder and back to 8 cylinder.
It may be necessary to compare the operation of the vehicle to a known good unit under the identical
driving conditions as the operation may be characteristic. Parts Information Part Number Description QTY
2015 - 2016 Corvette: Service Bulletin: Shake Or Shudder On Accelerati... http://www.corvetteactioncenter.com/...rint-1300.html
2 of 3 9/1/2016 9:43 PM Part Number Description QTY
24279497 Torque Converter: 6.2 (L86) – Truck and Utility 1
24279495 Torque Converter: 6.2 (LT1) Corvette 1
Article ID: 1300
Created On: Fri, Aug 19, 2016 at 3:33 PM
Last Updated On: Fri, Aug 19, 2016 at 3:33 PM
Online URL: http://www.corvetteactioncenter.com/...30-and-65-mph-
1300.html

tjs15

Thanks for posting this bulletin.

Dif

1. If you Scroll through the DIC in the Center Circle, with the DIC in Tour mode setting, there's an info view showing when it's in V4 or V8.
When in Auto, you'll see it change back and forth between V4 and V8.

2. What happens if you give it more throttle instead of accelerating Gently. ... Try more throttle.
It should then downshift to prevent it from lugging.
And then as you go faster, it should shift back to 7th, and if still accelerating, hit 8th.

Mine does Not want to go to the highest gear as soon as possible.
It stays in the lowest gear it can until I give it a good amount of throttle, or, I'm already going fast enough for it to shift to a higher gear with slight throttle increase.

If you watch it when it's in V4 in the DIC, you'll be surprised how long it will stay in V4 sometimes if you keep "gently" accelerating.
Give it more throttle, see if it stops shuddering.

Again just thoughts, and think you should at least get it checked.
Good info in the Bulletin.

Hope you get it sorted out

rickriada

This is quite informative info. TY! I'm going to read this enough so I can try these driving details that seem to be oriented towards a tech/service manager before I take it to any chevy dealer. Best Regards. TY!

rickriada

TY for providing this info.! I thought that AFM on the 2016 A8 vette would only work if the auto selector was set to ECO mode? If it isn't set to this setting, then AFM should not be engaged, right? Just my initial thoughts as I've been reading the responses on this post and using info from other sources regarding the AFM features on the C7 vette series. TY!

iclick

AFM (V4) only works in Auto regardless of the driving mode selected, even Track. V4 works only in Eco mode with the M7. The TC-related shudder only happens in V4 in my car and most (all?) others. I don't recall seeing a testimonial that shudder ever occurs in V8 mode.

Mine has been in the shop now for 17 days for a TC replacement. It shuddered on my way home from the dealer with <50 miles on the clock, persisted sporadically for about a year, then started doing it rather frequently about six months ago. About six weeks ago it got much worse and that's when I bit the bullet and took it to the dealer. The SM said it was the worst TC shudder he had seen yet, but he said he had done TC swaps only on models other than Corvette so far. My car only rarely exhibits the delayed engagement symptoms when cold and seems to be getting better with time.

I suspect reports of shuddering are increasing because (1) it usually shows up after a few K miles and many Corvette owners don't accumulate high mileage, and (2) some owners may misinterpret minor shuddering like I witnessed early on as road imperfections. When it gets worse they will take more notice.

I've had enough by now and once my A8 car is out of the shop I'm going to order a GS with an M7. When 2017 cars are showing up with TC issues it tells me GM doesn't have a grip on a fix.

Build date: 12/18/14
Odometer: ~4700 mi.