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Update on my GS. For the last thousand miles or so it has gotten much worse. Lots of vibration and more pronounced shudder. I hope to get it to the dealership this week.
Update on my 16 Z06 with 7500 miles. After 2 trips to dealer and 4 new wheels the vibration is worse and shutter is the same. Opened case with GM. GM had me return car to dealer and ride with tech again. Will call today and get status but getting very tired on dealing with this issue. Visited dealer 8/1 they have done nothing and really don't know what to do. Hoe do I escalate issue with GM.
Last edited by ronkellogg; 08-01-2017 at 02:50 PM.
I had an interesting situation last Saturday. We were driving in rural northwestern PA,in an isolated area. Using the paddles,I was not driving in an aggressive manner. Coming upon an area of rough pavement I downshifted from 5th down thru 4th to third,doing about 45 and slowing. My transmission raced and was stuck in gear. Not good since I was about 15 miles from help. I was able to gut it out. But,the revs were at a constant 4000 RPM in Drive. The Drive indicator flashed. I was able to drive and coast until I got to the gas station and cell reception. In addition,my engine light came on during this portion of the drive. On Star was absolutely worthless!!!!
We got a tow with AAA at 120 miles to home. When I got home I started the car to take it to my place and everything was back to normal! The next day everything was OK and I drove it about 15 miles. The garage said that it was a combo of things,possibly revolving around downshifting and some bad road that put the car in that mode. It will get a diagnostic next week.
On Star is worthless.
Norm
I had an interesting situation last Saturday. We were driving in rural northwestern PA,in an isolated area. Using the paddles,I was not driving in an aggressive manner. Coming upon an area of rough pavement I downshifted from 5th down thru 4th to third,doing about 45 and slowing. My transmission raced and was stuck in gear. Not good since I was about 15 miles from help. I was able to gut it out. But,the revs were at a constant 4000 RPM in Drive. The Drive indicator flashed. I was able to drive and coast until I got to the gas station and cell reception. In addition,my engine light came on during this portion of the drive. On Star was absolutely worthless!!!!
We got a tow with AAA at 120 miles to home. When I got home I started the car to take it to my place and everything was back to normal! The next day everything was OK and I drove it about 15 miles. The garage said that it was a combo of things,possibly revolving around downshifting and some bad road that put the car in that mode. It will get a diagnostic next week.
On Star is worthless.
Norm
Do you use the Range device that prevents v4 mode by any chance? That can cause that in very few cars.
Do you use the Range device that prevents v4 mode by any chance? That can cause that in very few cars.
I had a similar hi-rev condition while tracking my car. I wasn't using the paddles, but I switched from Sport to Track mode while moving and the transmission lost its mind. Was fine after a "reboot."
Yea, that's the thing with these cars, tons of computers. If you're in a situation where you may need a tow, rebooting several times can clear some error conditions. Just park it, turn it off, then restart. Do that about 5 times and see if the issue clears before calling the tow.
Still may be worth getting it checked by a dealer after, but could get you home a lot quicker.
I had an interesting situation last Saturday...
Norm
Norm,
There should be one or more stored codes from the transmission and OnStar (and many of the simple auto parts store scanners) won't read these. When the transmission controller sets one or more diagnostic codes it will send a request to the engine controller to turn on the CEL and to set a P0700 code which is a generic code indicating that additional diagnostic codes are stored within the TCM (transmission control module) and the dealer will be able to retrieve these codes to diagnose the transmission.
With the bumpy roads the dealer needs to take a close look at the harnesses leading to the transmission to see whether a connector isn't firmly seated or if a poorly placed harness has wear from frame contact. It is possible your transmission lost communications with the engine controller during the rough road situation and normally the transmission selects 4th gear as the "limp" mode gear but if the transmission were in 3rd when the problem occurs it may have locked into it. One of the 8L90 protection features is to inhibit shifts if communications with the engine is lost since without that communications link it cannot request power reduction when needed or "know" when a requested shift into a lower gear would result in engine overspeed.
Hopefully the trouble codes will lead the dealer to quickly locate and resolve the issue but I expect that there will be a code for loss of communications. If this happens and it was an intermittent condition then a single shut down and restart will reset the communications link and allow normal operation although the CEL should remain on indicating that a trouble code is stored.
I hope that your dealer can quickly resolve this issue for you.
Update on my GA. For the last thousand miles or so it has gotten much worse. Lots of vibration and more pronounced shudder. I hope to get it to the dealership this week.
Edit: just turned over 14,000 miles.
Before you take it to the dealership if you can find a safe place to cruise at steady speed in 8th gear and in V4 mode where the engine speed exceeds 1,600 RPM please try this as an experiment. At least in some of the AFM and A8 equipped GM vehicles lockup clutch modulation is disabled at over 1,600 RPM and it will be interesting to see whether that is true of the C7 and if that causes shudder to disappear.
Thanks to all who responded. My car is running just fine now. If this ever happens again I will know how to handle it better. With less than 3000 miles,I thought that I was in really bad shape. But,I will get it checked out next week.
As to On Star,the problem seemed to revolve around a rep that spoke with a very heavy accent that could not be understood.
Norm
I'm taking my '15 Z51 in tomorrow for the harsh engagement when putting it in gear after sitting for a while. I have had a new torque converter followed by a new 2016,17 transmission and torque converter. The overall performance and shifting has been fantastic, but the early morning lurch is ridiculous!
Well, after nearly two weeks, I finally got my baby back after a complete transmission overhaul. The engineers at GM sent my tech a newly revised valve-body along with a rebuild kit with clutch plates, seals, etc. Basically, this would make it a "Gen III" transmission. Anything produced up to this point sitting in a parts distribution center is prone to failure with a flawed valve-body IMO. I'm glad my tech was sharp enough to work this through. I hope I'm done with all these transmission issues. My C7 shifts even better than my "new" GEN II part number transmission now!
Last edited by stevettec7; 08-03-2017 at 05:59 PM.
Well, after nearly two weeks, I finally got my baby back after a complete transmission overhaul. The engineers at GM sent my tech a newly revised valve-body along with a rebuild kit with clutch plates, seals, etc. Basically, this would make it a "Gen III" transmission. Anything produced up to this point sitting in a parts distribution center is prone to failure with a flawed valve-body IMO. I'm glad my tech was sharp enough to work this through. I hope I'm done with all these transmission issues. My C7 shifts even better than my "new" GEN II part number transmission now!
Recall is highly doubtful - unless it becomes a safety issue, GM probably would never do a recall. I can see a TSB coming from this, but then again, it will only apply to those models exhibiting problems.
Isn’t it a safety problem if you can’t change gears?
Well sure it is, but I think that's a small number of occurrences. Sadly, it's almost to the point where someone has to die from a related issue for it to gain the attention of the NHTSA.
Last edited by stevettec7; 08-03-2017 at 07:11 PM.
[QUOTE=stevettec7;1595284594]Well, after nearly two weeks, I finally got my baby back after a complete transmission overhaul. The engineers at GM sent my tech a newly revised valve-body along with a rebuild kit with clutch plates, seals, etc. Basically, this would make it a "Gen III" transmission. Anything produced up to this point sitting in a parts distribution center is prone to failure with a flawed valve-body IMO. I'm glad my tech was sharp enough to work this through. I hope I'm done with all these transmission issues. My C7 shifts even better than my "new" GEN II part number transmission now!
So happy to hear that this turned out great for you. Now go and enjoy your "baby". Thank you for posting your invoice which shows the PN of the valve body, plates, seal and fluid used. This info may come in handy to all of us that are monitoring the tranny failures on this forum for future reference with our dealerships. Wonder what alloy changes were made in new parts version to avoid future clutch hot spots.
Heidi
Save the Wave
07-31-2017, 08:01 AM
