torque converter
- Thread starter xviper
- Start date
It sounds like something before the transmission at that point. Driveshaft/torque tube sounds logical. The rubber flex u joints seem to be the problem. I have read many issues with these on the automatic cars through the US Corvette and Stingray forums. It appears to be a well known issue with GM.
Xviper,just wanted to give you an update on the 3rd gear bump in manual. Software updates, transmission triple flushes , two torque converter and one transmission / torque converter replacement did nothing to fix the bump at Aprox 2200-2500 RPM accelerating in M3.
Over the 30 months I owned the MY 2015 base A8 I did have the opportunity to drive a few other cars for test purposes and speak with several different techs at the different dealerships that did the work.
At two different dealerships the shop foreman test drove my car with the computer hooked up to it after I demonstrated the "bump" in M 3. The first shop reported that the bump occurred in M3 at the point of TCC apply.
At the shop last February I gave the foreman all the information and he also said the bump was at TCC apply in M 3. He reported he discussed this with GM TAC , USA, and they told him it was normal.
A couple of other base C7's that I drove, one a MY 2015 the other a MY 2016, had the identical bump.
I also drove a couple of cars, with a manager with me , that did not exhibit the bump.
I recently traded in my 2015 for a MY 2018. I immediately tested for the bump and it is there but not as pronounced as it was in the 2015.
I think the reason we don't see the bump when driving with the shift selector in D is the tranny will shift to 4th prior to the bump point. On my 2015 car in M , the harder I accelerated the higher the RPM was at the bump point and it was not as obvious a bump as compared with shallow throttle angle acceleration.
FWIW, my final thoughts;
1) it appears TC replacements and tranny replacements do not appear to fix the "bump"
2) my 2018 bump in M3 is softer than it was in my 2015 and if I did not know what to look for I probably would not have noticed it.
3) Most drivers paddle shifting in Manual are doing a bit of spirited driving . The more you stick your foot into it the less noticeable the bump is and it happens faster. I suspect many owners have the bump and in spirited driving don't even notice it.
4) I can not explain why I was able to find two cars that did not bump and I did test at a shallow throttle angle where it is most noticeable.
5) That having been said, if the mild bump in M3 in my 2018 does not get any worse and it is the only drive line issue I will not be taking it in for service as I believe it is a characteristic of the A 8 design.
Just my experience, hope it helps.
Baby Ray, it sounds like you have two problems. The transmission bump that is being described in this thread, and a solution to which does not appear as yet to be known.
But seriously, if your car is causing a vibration when revving in park, you have another serious problem that needs to be addressed. Perhaps a loose or cracked flex plate? A loose motor mount, or something is out of balance internally in the engine.
But seriously, if your car is causing a vibration when revving in park, you have another serious problem that needs to be addressed. Perhaps a loose or cracked flex plate? A loose motor mount, or something is out of balance internally in the engine.
They have changed the torque converter tube now. All seems good after driving about 300km testing it out in all modes. Auto or manual. They said the flex plate was fine. They claim there a bearing on the one end of tube that was getting loose and causing the vibration. I guess we'll see what this one does.
3rd gear thump (manual mode) still there. I'll see how this goes for now.
So really they do not know the real cause of the issue since the stutter, or thump as you call it, is still there. I strongly suspect from all the reading I have been doing all the other issues are symptoms of a design fault that is causing the stutter/thump and the other issues people are having are coming after like yours did because of the former. Typical of any of the big automakers not wanting to admit a real problem and fix. Money is important.. customers not so much.
At least the one problem Zig is fix. But not the Thump. Is this gonna cause the vibration to come back or was that really just a quick fix. I wonder if the tube was a newer version or old and going to happen again???
Certainly possible. The 2nd letter will come from my lawyer in that case.
Nice to see the thread cool off. I streamlined it a little as I don't really want to read that stuff on the forum and it doesn't add anything to the topic. I understand that debate and conflict can happen but it seemed to exceed the level of respect I expect between our members and almost always just naturally see from everyone. If anyone has any questions, I welcome you to send me a message and we can discuss.
I'll add my opinion to this thread, and it's just an opinion on the slip in 3rd gear how I see it................. Just get a manual transmission everyone. Automatics are for wusses!
Just kidding. Although this issue may be slight and not affect the function of the vehicle itself, it is a flaw noticed by some people. When buying a new car, you expect for things to work as they should. Now if GM sold the Corvette with the A8 and said, "You'll notice that in 3rd gear when in manual mode, at light throttle applications what feels like a bit of a slip is just line pressure changes and clutch engagement with the band groupings between 3rd and 4th gear and the programing requires a touch of slip to change ranges in the transmission." Then I would imagine it would be easy to accept this as normal. But instead, the car is sold with the expectation that it should work equally in all gears and modes so I understand why people look to the dealer to fix, what should be a simple software issue, in their transmission. However, with GM's inability to diagnose and repair the problem and then use people's vehicles as a Guiney pig to test different fixes, I can see why something minor is ballooning into something larger. It may not be a hole in the armpit of a suit but I could see it being an ichty tag on the back of the neck that slowly irritates if the right undershirt isn't worn.
I'll add my opinion to this thread, and it's just an opinion on the slip in 3rd gear how I see it................. Just get a manual transmission everyone. Automatics are for wusses!
Just kidding. Although this issue may be slight and not affect the function of the vehicle itself, it is a flaw noticed by some people. When buying a new car, you expect for things to work as they should. Now if GM sold the Corvette with the A8 and said, "You'll notice that in 3rd gear when in manual mode, at light throttle applications what feels like a bit of a slip is just line pressure changes and clutch engagement with the band groupings between 3rd and 4th gear and the programing requires a touch of slip to change ranges in the transmission." Then I would imagine it would be easy to accept this as normal. But instead, the car is sold with the expectation that it should work equally in all gears and modes so I understand why people look to the dealer to fix, what should be a simple software issue, in their transmission. However, with GM's inability to diagnose and repair the problem and then use people's vehicles as a Guiney pig to test different fixes, I can see why something minor is ballooning into something larger. It may not be a hole in the armpit of a suit but I could see it being an ichty tag on the back of the neck that slowly irritates if the right undershirt isn't worn.
Well put Riley. The only thing I would change is GM's inability to GM's desire. I have a very hard time believing they do not know exactly what the issue is already but just don't want to open up the Bottle of Cost Genie's to actually fix the problem. And there have been documented verified reports with the A8 where the problem became much worse and required change out of other internals than just the TC and other components just to get the transmission back to where it "only slipped like everyone else's". So some people have the itchy tag and some do have the hole in the armpit. Mine is just the itchy tag right now but I find it very annoying since that tag is attached to a fancy suit from Brooks Brothers worth $100k and not a $20k suit bought at Tip Top.
I have the same issue with the third gear bump. Spoke to a GM Engineer and he explained to me that it is normal and not just the Corvette. I find that if I drive the car in M mode like my grandmother I can feel the bump. If I drive it like a scared rabbit and keep the rev's up the bump goes away. I also spoke to him about the reason I use M mode was because the A8 seemed to me to be a little on the sluggish side. Guess you can blame the EPA for that. Car shifts at lower shift points so as to post better gas mileage to make the Environment Police happy. Just the nature of the beast. I'm not going to worry about it and going to drive it and have fun!!!
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