is having the 'instant fuel economy' screen up the only place you can monitor DOD status?

also is there a specific way you can command v4 to come on (other than carefully prepared drive conditions)

 

hope you are wrong ..my 2016 a8 produced august 2016 ..

This really sucks if my damn car with 400 miles on ..down the road and who in the hell knows when is going to be torn apart ...kinda takes the fun out of it ...

And why the hell not just have a recall ....i will tell ya why ...so gm can save money ...and save face ...because a recall of this magnitude would really hurt sales and resales

my fault though for buying a gm ....

 

After reading more replies in this thread and gaining a better understanding of the shuddering syndrome I'd like to amend my previous message (#94). I stated that I had not noticed any shuddering, but I do recall that when I first bought the car, driving it home from the dealer (60 miles away) I noticed an occasional very light shutter at highway speeds, almost assuredly while in V4 mode. It reminded me a bit of older cars I had owned that had faulty u-joints, except not as noticeable, very short-lived, and not repeatable by applying power. I didn't notice it again over ensuing months so I put it out of my mind until a week or two ago.

The other day I did notice a similar shudder on two occasions while cruising, around 40-60 mph and undoubtedly in V4 mode. As before, the shudder was brief and at the time I attributed it to the road surface. It might have happened at other times but I just didn't notice it, as it isn't very pronounced. The next time it happens I'll make a mental note of the circumstances surrounding its occurrence.

Based on what I'm reading here this is considered normal, so for the time being I'm not thinking it is indicative of an impending A8 issue.

 

Part of the problem with the A8's and the torque converter failures is getting a dealer to properly diagnose the problems you are having with your transmission. The first dealer I took my car to said that they noted no problems with my transmission. I found out that another dealer had checked out two C-7, A8's and had ordered new torque converters. I went to that dealer and the tech checked out my car and said that it was the torque converter causing my problems and he ordered a new torque converter. He also said the problem was a bad o-ring in the torque converter. He also advised that he had been on the phone with GM several weeks prior and GM had determined the problem was a bad o-ring and was giving the OK for new torque converters. It appears GM is not going to have a recall or inform all of the chevy dealers about the problem with the A8's. Make sure you go to a dealer who has already diagnosed the A8 problem as a bad torque converter.

 

This would be correct 2016 built before November 15th are also equipped with the bad version of the transmission.






.

 

My 2015 with about 13000 miles is doing the same thing. The RPM fluctuate about 100 rpm's all the time. I have put it in "M", and paddle shifted it, and still the same thing. I can see the AFM kick in when in auto, but this is an entirely different problem that some of us are having.

Dealer put it on the computer, and drove it..said they can't fix something that "ain't broke". I'm just waiting!

 

I think you meant "August 2015"

 

You have ZERO facts to back up that statement.


.

 

What about the part numbers on the transmissions???

 

yes thank you aug. 2015 ..was my build date ...sad to say ..

This junk may be getting dumped ....rather soon if possible

life is tooooo short and i am toooo old for this high school stuff

 

[QUOTE=bbcb;1591463863]yes thank you aug. 2015 ..was my build date ...sad to say ..

This junk may be getting dumped ....rather soon if possible

life is tooooo short and i am toooo old for this high school stuff

 

I'd like to offer another update after a drive today. It'll be long but I don't want to leave out any details. I earlier stated that I was not getting any tach fluctuations and demonstrated it with a video taken during a ride on the interstate at around 65mph.

In ambient 55° temps I entered the interstate about 5 miles from my house, then drove 5 miles to the next exit. By that time both oil and coolant temps were at 185-190°, almost normal (195°) for both. On that stretch at about 75mph (10mph faster than before) with cruise engaged I noticed both a bit of shuddering and about the same level of tach oscillation as Earnest T recorded in his video, about 50-100rpm at a fairly regular rate of about once every 1-2 sec. I could not feel it but it was evident on the tach. I did feel some shuddering on that stretch.

I did a u-turn at the next exit, drove about 10 miles at around 75mph, and noticed more noticeable shuddering, occasionally at a rather disconcerting level, but only in V4 mode and never lasting more than a second or so. It would repeat sporadically, but when I shifted to Manual it would change to V8 mode, RPM dropped a tad (~50 rpm), and the oscillations stopped, as did the shuddering.

I turned around and drove another 10 miles back where I came from and although the tach movement remained (V4 only), the shuddering was not apparent. Thinking it might have been the road surface I turned around at the same point as before and the shuddering remained not apparent. That would seem to rule-out road imperfections as the cause.

I noticed some shuddering when I first bought the car (Feb. 2015) at moderate interstate speeds, but didn't think much of it at the time. I also noticed it a bit a couple of weeks ago, but not once during the warmer parts of the year.

Here are some questions and observations based on this limited info:

1. Since both shuddering and tach movement occur only in V4 mode, should that disqualify the A8 as the origin? OTOH would the TC be locking in Manual (V8) and not in Drive (V4), and if so does that return the A8 to the suspect list? I'm assuming the tach movement has always been there under these conditions but I just never noticed it, as there is never any sensation that it is happening.
   
2. Since it was only noticeable before the car achieved normal operating temps and I've only noticed shuddering in cooler ambient temps, I'm wondering if it might be related in some way to temperature. On my run today the shuddering did go away after about 20 miles of driving and after it had reached normal operating temps.
   
3. Since the shuddering was first noticed in the first 50 miles of the car's life it obviously isn't a new phenomenon.
   
4. The shuttering doesn't seem to be related to the tach oscillation in any way, and isn't happening during a transition to or from V4/V8.

It'd be interesting if those of you who've noticed the shuddering and tach oscillation could take my notes above and compare them to your experiences.

 

It's locked either way, but slips in auto to make the transitions from V4 to V8 and back.

 

Just had a conversation with the OP Trans was re installed yesterday dealer told him they wanted to change the fluid and filter that was yesterday. OP has not heard from the Dealer since.

 

One of the symptoms of a bad torque converter - Shuddering - feels like running over a rough road when you are on a smooth road. THIS COMES AND GOES WITHOUT WARNING. Mine also shuddered for about 2-3 seconds, stopped for several seconds, and shuddered again for about 2-3 seconds. Continued to do this while in cruise control on the interstate at around 70-75 mph. You can feel the shudder in the steering wheel and gas peddle.

 

The reason I asked is that I noticed that while the tach is oscillating in V4 mode (Drive) the movement stops and tach decreases ~50 rpm when shifting to Manual. It stays in 8th gear during the transition.

 

thanks for taking the time to write such an insightful and helpful post.

 

I also have a 2015 2LT. I had the same exact issue. I took it to the dealer and they diagnosed it as a bad torque converter. They replaced the TC and it's been fine since. They did not need to replace the transmission. The bouncing tach needle was the first indication that something was wrong. Whatever the root cause it quickly deteriorated to the shuddering and continued to get worse. It's fine now.

 

Thanks, but if so I must say that after my short drive today I'm left more confused than ever. For example, is the shudder a byproduct of the A8 or AFM? Same question for the tach oscillation. The GM TSB posted earlier says the shudder is okay if in V4 mode only, but what about the tach movement? If the shudder is okay, what exactly is causing it?

The consolation is that my tranny shifts great and generally behaves very well, but all the minor weirdness I've described has me wondering. I'm sure with threads like this one their meaning will become more clear in time. One consolation is that we have a five-year warranty on the drivetrain.

 

Do you or anyone else know what's involved in replacing a TC? I presume it dictates a tranny removal, so how invasive is that? In a C2 and most other RWD cars of that era it was quite easy, but I would bet it isn't in the C7.

Tomorrow I'm going to call the SM at a big Corvette dealership nearby and have a little chat. I'll report what I find out.