thehad

Been a while since I posted anything but I just made a trip today and got the best gas mileage in any truck that I have owned. I made a 214 mile trip with a moderate tailwind of about 12 - 16 mph and outside temp of 70 - 80 F and got 26.1 mpg with the cruise set to 70 mph. I don't remember what my best 25 and 50 mile were but I think the 25 was 30.2 mpg and the 50 was between 28 and 29 mpg. I just broke 13000 miles on my truck on this trip as well. My city mileage is not that great , averaging 14 mpg, but I also have a lot of short trips and very little freeway driving during the week. Overall, I'm very impressed with these new trucks' fuel economy.

gjk1932 I think there is a problem with all Goodyear tires that come on these trucks. My truck came with the Goodyear Eagle LS-2 tires. I am glad to hear that some of you have swapped the tires to another brand and have either fixed the issue completely or reduced it to a non-issue. I have no further updates since my last post since I haven't made any trips after getting my truck back three weeks ago. I've been working 70+ hrs a week and haven't had any time to just get out on the road to test the tires or make a trip. I may get a trip in this weekend, so I might have a conclusion on the fix I got next week. I've been thinking about replacing the tires but haven't had the time to do so or the want to spend the money. I'll make that decision after I get a long trip in.

Got the truck back today. It ended up being a tire issue after all. Apparently the tire shop didn't check for tire roundness like they were supposed to do. I had one tire that was way out of spec. They said that the road force maximum allowed value on trucks is usually around 26 lb and that tire was over 32 lb and couldn't be brought into spec. So they ended up replacing it but they went through two tires since the first one they put on had an even higher number - 64 lb this time. The second tire came in at 19 lb. There is still a small amount of vibration but at 80 mph it is still less than it used to be at 75 mph and only starting to be "noticeable." I won't know more until I am able to get out on the highway for a longer trip. I may end up replacing all of the tires with a different brand but for now the ride is much better. What made me turn away from a tire issue is that I had the tires rotated with no change in the vibration and the last time they balanced the tire, they were supposed to check for tire roundness as well. They said what was happening was a torsional vibration. The tire was feeding off the opposite tire on the front of the truck causing the variation in the vibration that I was feeling. Basically as I turned the tires would go in and out of phase with each other, creating the oscillation in the amount of vibration that I was feeling. When in phase, they would add together, amplifying the vibration and when out of phase, they would cancel each other out - almost since it never when away. This is a new one on me as I have never had this issue on any vehicle (this is my 7th vehicle). The service manager came out and talked with me a bit on this issue. He said that the re-time of the drive shaft that they performed on my truck usually fixes the issue on about a third of the trucks. The other fixes have been new drive shafts to new axles if the issue is not a tire or wheel issue. My suggestion to everyone is to make sure your tires are not too far out of round first, even if this requires going to multiple tire shops just for the sake of a second opinion. Hopefully this helps some of you.

Heard back from the dealer on Friday. They and the regional engineer both agree that there might be something wrong with the axle. So the engineer is having them check everything from alignment of parts to part thicknesses/balance to see if there is something out of spec. Hopefully I will know early next week on what they find.

The service tech at my dealer told me the same thing. He said that it felt like road vibrations and that I shouldn't put too much more effort into chasing this down in fear of driving myself crazy with it. I would have taken it back in last week but last week was completely terrible for me. Hopefully in the next couple of days I will get some time to take it in and discuss with them options. Reading all of these posts since my last has given me much more ammo to go to them with. I have also made two 10hr round trips since getting my truck back and I can tell you that it is not road vibrations. I will keep y'all updated on what I find.

The drive shaft re-time did not fix the problem. It still vibrates exactly the same as before. I talked with the service tech and he seems to think that it is road vibrations that I am feeling. I will have to talk with them next week and see what else they can do. I still think that it has something to do with the rear axle. The amplitude of the vibration changes only when I turn and remains constant at whatever level it reached in the turn while driving straight. So sometimes it is really bad and sometimes it is barely there at all but it never totally goes away.

Got a call from the dealer today and they said that their technicians also confirmed the vibration as I described it. They had to call their regional tech and he suggested three possible things that it could be. The easiest of them was to re-time the drive shaft. I forgot the third thing that they mentioned but the other was to have the drive shaft balance checked. So, they took it off, checked for any manufacturing defects and/or damage (found none), turned it 180o and put it back on. They said that they took the truck out and test drove it and that they did not feel any vibration after. So maybe it is just an alignment issue causing all the vibrations. I won't know until tomorrow since they still have the truck. I will let y'all know when I get it back if this fixed the issue or not. I will be making a trip this weekend, so I will be able to fully test it out. I'll keep y'all updated.

My lifetime average right now is 18.8 mpg. I average about 14 mpg in the city since my commute is 2.5 miles with 5 stop lights in between, two of which are on about a 2 min cycle. My best tank is 24.2 mpg at 69 mph using the a/c. My best 25 mile average is 28.3 mpg, with my best 50 mile being 26.6 mpg. I calculate all of my tanks manually since my DIC is all over the place. It has been right on a couple of times and has been as much as 2.3 mpg off! It usually sits between 0.5 - 1 mpg off. My truck has the 3.42 gears and 20" wheels, all stock.

I have the 20" Texas Edition wheels as well. I don't think mine has anything to do with the wheels since I just had them rotated and the vibration is still exactly the same. I will hopefully know more on Wednesday when I take my truck in to have them look at it and see if they can pinpoint where the source is coming from.

I just had my tires rotated today and the vibration is still in the rear of the truck. The only thing that I can think that it is now is the axle. I will be taking the truck into the dealer next week to have it looked at. I will keep you all posted on what they come up with and if it helped or not.

I have this very same issue on my 2014 Sierra 2WD. I may have a solution (theory) to why it seems to go away sometimes and return other times. I have noticed that on my truck the vibration will get better or worse as I am turning at highway speeds starting at about 65 mph and continuing upwards of 80 mph. I noticed the vibration one weekend on a trip and got the tires balanced the following weekend. The problem seem to be actually worse than it was when I took it in, so I started to really pay attention to it. I started noticing that it would be better occasionally and then worse. I hit a really long bend in the road and that is when I experienced the reason, at least on my truck, why it seems to be better/worse. I felt the vibration cycle from almost gone to really bad and then back to almost gone. It appears that there is a balance issue between the right and left wheels. As they turn at different speeds while turning, they are able to align with each other producing more vibration or offset from each other canceling out the vibration. It never totally goes away on my truck, though. I haven't taken my truck into the dealer yet but I plan on taking it in next week to see if they can check some things out. On the weight subject, I almost daily haul around 4 other guys during lunch and still have the vibration though the speed in town is only 65 mph so I can't say if it is worse or better with the weight since it is only starting to vibrate at that speed. Edit: I forgot to add that I have since had my tires balanced twice with no change to the vibration.