have a 2017 Canyon V6, 4x4 SLE started doing the same thing at about 12000 mi continually getting worse! The worst shudder shaking is at about 55 steady speed with slight off and on exelaration to hold the speed in cruise or whatever. However it will do it at nearly any speed at times. Yes it helps when cruising at hwy speeds to downshift to 7th but that’s not what you should have to do! Besides it will do it in 7th too when it pulls just right up a grade.I thought the tires were out of balance and took it back to the dealer which re-balanced all of them and didn’t help at all. So I have another appointment next week. Going to give them a ride and shake their teeth out to show them what it is doing! The truck only has a little over 14000 mi. On it so this is completely unacceptable! And getting worse! I noticed the transmission temp. Probably already damaged the internal parts... After all I have read on this forum and other about this I don’t think I’m going to go along with all the “we’re going to fix it crap” and tell them either buy it back or give me another “new” different kind of truck and transmission maybe like the Duramax since it has the 6 speed in it.
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update: Took it to the dealer another day and had the service manage ride with me to show him and have it documented that it will shake your teeth out while cursing. however when he got into the truck he said "I'll take a ride with you but I am well aware of this problem, I know what it is doing.” I'm sure he does... he then told me they have to go through "the process" and do triple flush to see if that fixes it. said it probably would but if not they would put a new torque converter in it. I said if that will for sure fix it why not just go ahead and put it in there? GM says have to do the flush first... yeah$$$ I told him even if it fixed it how much damage has already been done to the longevity of the truck? Oh he said the transmission is fine... yeah sure. I had the lemon law book laying in the console so he could see it but said nothing. He knew what that meant... this whole thing makes me sick. I have always trusted GM and now they are trying to cover up an obvious recall issue. sickens me.
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Update again:
Next visit to the dealership to do the triple flush on the shuddering transmission. while I was in the lobby waiting (only a few minutes) reading my lemon law book; the service manager came out and said it looks like we have an update on fixing your transmission. now GM is saying go ahead and skip the triple flush and replace the torque converter. well well, that's what I asked about to begin with if they knew it would fix it, why not!? so they kept it about a week to replace the torque converter. I've driven it about 700 miles so far and it is very smooth, no shaking or shuddering so far. the thing that worries me is how much damage did it do to the rest of the transmission driving it with the wrong fluid in it and the torque converter going out (metal shavings pumped throughout the transmission) what is going to happen say 50,000 miles down the road? this was to be my last new truck since I am retired and on a fixed budget. I won't have the money to pay for replacing a transmission... concerned, don’t know what I should do even if it seems like it's fixed?
Any advice would be appreciated; thanks