To all of you: I posted POSSIBLE FIX for a reason. I don't have any issues with mine and I'm not going to read through 200 pages, I was just trying to help and give incite on this situation. I'm not a GM rep and its not on me so I really have no reason to feed anyone bs. The fact of the matter is this did fix his problem and his truck is running smooth now, take it for what you want.
I will ask that but I believe it was not at 65-70 mph, his was a lower speed issue. It wasn't ring gears because they said the only replaced motor mounts. That may mean some were missing or not properly installed, there is not telling.
I'll get a build date off his truck when I visit him next.
If your motor is vibrating and is not properly secure it will absolutely increase mpg after fixing it. Pull a couple of yours out and report back to everyone... Maybe you'll even get better mpg, you should definitely try it! I even hear taking off your lug nuts will help from the weight reduction, try that too but only at highway speeds.
Rule out what you want but this is what happened.
I have to see if he still has the paperwork. I know he wont have the part numbers but possible to get the recall number.
You might be right, I haven't visited this page for a long time and definitely did not read through almost 200 pages. Just hoping to help, that's it.