Harold Rutherford

I purchased a new 2018 Sierra SLT 5.3 8 speed in October I noticed when you first start it up and put in drive the transmission slips and the bangs into gear even if you warm it up first after a couple of shifts it operates as normal. I drove it on my first trip all was well until i exceeded 65 mph then a tight vibration started and got worse the faster I went especially when going up a hill, naturally I thought a tire was out of balance. When I took it to dealer for the first oil change I told them about the vibration so the rotated and re balanced all tires, they replaced 1 tire said it would not balance. I took another 940 mile trip but had the same vibration over 65, took it back to dealer they keep it 2 days and said truck was in GM's acceptable amount of vibration so did nothing. I have taken it back 2 more times still no fix because it's OK to have some vibrations in truck. This is BS! I have had a 1998, 2000, 2002, 2005, 2007, 2014, 2016 and now the 2018 and the 8 speed transmission is the only one that had this problem. What is "acceptable vibration" suppose to mean? It feels like a out of balance drive shaft but after researching this problem I find out it's the POS 8 speed. I went to buy a new 2019 Sierra but hated the interior, all were Jet black (ugly) and 2 had Chestnut, I wanted the Cocoa Dune like I have had in my last 2 trucks but it's not available so I bought the 2018 and saved $14K. I love the truck under 65 mph but the vibration is driving me crazy at higher speeds!

I had 30,000 miles on the 2016 when I traded it. I have now had the 2018 4 months 4,400 miles and so far it is fabulous no weird noises and much quieter than 2016. I am once again a happy GMC owner.

Sorry guys I traded my 2016 GMC Sierra SLT 1500 on 10/06/18 for a new 2018 Sierra SLT SLT 4x4 and no longer have any problems. The above post did fix the AC noise permanently so if your still going crazy from the noise do the simple repair only takes about 20 minutes and you'll never regret it. I posted the video of the original problem a while back not sure where it went maybe GM took it down, I will repost the URL for you guys.

My fan on recirculate is loud but on auto quickly goes to outside air and is now quite maybe because mine is a pick up truck and requires a smaller fan than the SUV's. Thanks to you I love my truck again, I had a friend ride with me today that owns a 2014 Toyota Tundra and he was shocked on how much quieter it is now. He used to harass me for buying a GM truck until his had to go to shop with a smoking engine with 40K now I am doing the harassing. lol

Update on A/C noise 3 weeks after installing the duct seal around lines (see pictures above) outside where the lines enter the firewall the noise has disappeared, gone, quiet. I never realized the noise at low speeds was also there at any speed because now the Truck is much quieter all the time! Finally I love my Sierra and would like to thank Jim again for the simple common sense fix. I hope GM reads these post so they can save others from total brain damage from the noise from their poorly designed A/C systems, not to mention my 5 service trips, unnecessary new compressor, new fan motor and rental cars they could have fixed it for less than $7 and probably saved hundreds or thousands of customers.

My 2016 GMC Sierra 1500 has had a loud noise inside cabin and GMC service has tried everything to fix it, they new compressor and fan motor none helped. It has been in 5 times for repair but no one could figure it out. Finally on another post I saw a fix so I tried it and so far it has eliminated the noise. Cover the incoming metal lines outside under the hood with 1 lb bar of Duct Sealer (found it at Home Depot in electrical dept) form it around metal housing and tubes where lines enter firewall takes only a few Minutes to do. After 2 years of agony I could not believe that it stopped the sounds but it did. I will attach pictures of solution good luck!

Thank you Jim, I tried the duct sealer bar from Home Depot as you suggested and so far it has stopped the AC noise in the cab. I can't believe GM can not figure this out but you did, you're a GENIUS! Maybe GM will give you a job fixing their un-fixables lol I will attach the pictures of my fix because it is different set up from your pictures but thanks again for the suggestion and solution to the most annoying noise.

I will get some of this putty and try it, what do I have to lose except the cost of the putty. If this works GM should do this under warranty and save their customers from going berserk! I have returned 5 times for this problem maybe you have solved it for me. Thanks (praying for good results)

Jim, the last technician did get in the truck with me and he did acknowledge the noise he actually rerouted the line going into the firewall away from all metal and it helped somewhat. I will give them credit they have done everything they can to stop noise from changing the compressor, fan motor and rerouting AC lines it has reduced the noise level to almost acceptable. I think GM should get on this problem and fix it and stop denying there is a problem I have purchased 7 brand new Sierras first one to give me any problems. I still love my truck other than this annoying AC noise. Keep hoping for a solution soon. If and when they figure it out I hope they will man up and recall these trucks.

If you have a tech that knows how to fix the AC noise see if he will share his solution with us.

I did get in the truck with the tech and service writer, they hear the noise but can't pin point it to fix it, hopefully GM will figure out the problem and come up with a solution in the future. If anyone can figure it out maybe they will post it and I can pass it on to the Tech. My 2014 Sierra had dim lights after 2 years they changed them out to a new brighter lights that was much much better so there is still hope.

Update on AC noise: I got my truck back from the dealer today (4th time in for noise) they had it 4 days and stated they could not duplicate noise so I assume it is un-fixable just have to keep the radio blasting when not on highway. It's a shame because other than this very annoying noise I love my truck.

No Jim I have another appointment next week for one more attempt to try and fix the loud compressor noise I will let you know.

As the weather warms I have noticed the A/C noise is getting loud again almost as loud as before the new compressor and fan motor, this is driving me crazy! I have purchased 7 new Sierras and this 2016 is a first for A/C noise. Too bad because I love the truck but really starting to change my opinion, whats worst is no one knows how to fix it. GM needs to buy these back if they can't be repaired.

My 2014 Sierra never made the noise and my 2016 was quite the first year, still have the noise (not as loud) after they replaced the blower motor and the compressor. I will look into insulating the lines, let us know if you figure it out because GMC has no clue.