Mine started shuttering at 25,000. Mobile One flush did nothing. Torque converter was replaced and transmission is great now--it even got rid of the occasional "clunks" in the parking lot.
My local Mobil has 93 premium with 10% ethanol and 89 ethanol free. I get my best gas mileage from the 89 (22 mpg driving 75-80 with 6.2 NHT). Ethanol free gas has more BTU's (energy) per gallon than 10% ethanol gas. For the same price, I would use 91 ethanol free.
I have 2017 Sierra 6.2/8 speed NHT that developed "the shudders" at 25,000 miles. They changed the transmission fuid but no change. Torque converter was changed 2 weeks ago. Now it is incredibly smooth. There still occasional light clunks between 1-2 gear in parking lots, but I think most 8 speeds do that. I read somewhere that when making the torque converter, the manufacturer was damaging an internal seal and fluid was not flowing properly and that the new torque converters have a different part #. I'm not sure if all of that is true, but I would hate to have to replace torque converters every 25-50,000.
sigmonster replied to Sierra Dan's topic in 2014 - 2018 Chevy Silverado & GMC SierraI have a Sierra SLT 1500 6.2 8 speed. I drive 70-80 mph on highway. My truck runs fine on any octane rating though I use premium when towing. Using 93 premium 10% ethanol my high mileage is 21. Using 87 regular 10% ethanol my highway mileage is 20. Using 89 midgrade ethanol free my highway mileage is 22. The 89 ethanol free costs the same as premium, so that is what I usually run since it is more efficient. The cheapest cost per mile is with regular 10% ethanol. Ironically, I had a 2014 5.3 6 speed that only got 19 mpg highway using regular!
An update to my truck. 2017 6.2L NHT Sierra. It started shuddering after 25,000 miles (and a week of towing). First the dealer changed the fluids and I drove it 200 miles. No change in the shudder. Last week they changed the torque converter. It was at the dealer 4 days and they listed 21.5 hours of labor on the warranty claim!! It now is smooth as butter. Still an occasional clunk when cold in a parking lot (another 8 speed issue). Love my truck again.
I got the new transmission fluid and filter yesterday. On the way home there was still a little shutter (especially going uphill at 25-35 mph). This morning I didn't notice any shutter going to work. It is at least 90% better if not totally resolved. I am supposed to drive it for 200 miles--if there is still shutter I will call them back.
A big thanks to this forum for all the information shared. I have a 6.2L NHT with the eight speed. At 25,000 miles I noticed a slight shudder (especially going uphill). Without the info of this forum I would have blown it off. I took it to my local dealer (Everett Chevy in Hickory NC). They made me drive it with Ed, the service manager (who I expected to tell me it was normal). The service manager noticed it more than me and said it was good to address it early. I am scheduled for an inspection/fluid change next week. If that doesn't fix it, then a new torque converter. Thus far a very pleasant experience with the dealer which is why I mention them by name.
I have driven a gas 2500 and a Max Tow 1500 SLT with 6.2. I got the Max Tow 1500. The 1500 has a much better ride (unloaded at least), better fuel economy, and a shorter turning radius--it is a better daily driver. The 1500 pulls my boat (5000-6000lb) as fast as I want (70-80) mph even uphill if needed. I love the large mirrors.
I have the 20" Defenders on a 2014 SLT. Love them. I have the 18# Sumitomo Encouonter HT on a Jeep Grand Cherokee. When i first drove the Jeep I thought the tires were almost identical to the Michelins in ride and quietness. I haven't had them long enough to comment on longevity or traction, but thus far they are a great tire and an even better value.
I have a 2014 5.3 with 6 speed and 3.42 rear end. I also have a 2017 6.2 with 8 speed Max Tow (I believe 3.42 rear end). I can say that my 6.2 with 8 speed and Max Tow does get better gas mileage (about 1-2 mpg or 10% better around town and on highway). Unfortunately, the 6.2 runs best on 93 octane which costs 20-30% more than regular gas. I have mixed 93 and 89 octane with no decrease in mileage. I haven't tried regular gas--I don't want to mess up a good thing.
I bought a 2014 Sierra 1500 crew cab short box SLT 4x4 Z71 with 5.3 engine, 20" wheels, 6 speed, and 3.42 rear end. It was the best truck I ever owned and was zero trouble after 45,000 miles. I put on an ARE camper top and Michelin LTX MS2 tires. It got 21-22 mpg at 70-75mph, 19-20 mpg at 80mph, 16-17 mpg around town, and 10 mpg towing a 5000 lb boat 70-75 mph. It was quiet, smooth, and drove very well (good feel of the road especially with 20" wheels and Muchelin tires. I planned to drive it another 3-4 years. Then my son totaled his car in a snow storm. He takes his insurance money (plus some savings) and wants to buy my truck. I'm flattered that a 23 y/o would want what I drive and as a parent I know he is getting a great used truck. Besides, that means I have to get a new one! My local dealer (Everette Chevy GMC) find a suitable replacement 2017 Sierra crew cab short box 4x4 SLT. I do want this truck to be a little different so it has NHT (Max Tow), 6.2 engine, 20" wheels, 8 speed, and 3.42 rear end. These are my thoughts after 400 miles. NHT and Z71 ride/handle very similarly. Z71 has a little more feel of the road (perhaps due to Michelin vs Goodyear Eagle tires) and NHT is a little more bumpy in the rear end. The NHT springs and axle are heavier duty though they look identical to me. The NHT is sprung 1" higher in the rear (but no camper top on that truck- it is on order). LOVE the tow mirrors. 6.2 8-speed obviously has better acceleration, but 5.3 is no slouch. Both transmissions will "clunk" on occasion. The biggest (pleasant) surprise has been fuel economy in the new truck. It was initailly filled with 93 octane and when half empty I topped it off with 89 octane. No knocking (and I will eventually try 87 octane). Around town I am getting 18-19 mpg around town and 22-24 mpg on the highway at 70-75mph (with a 50 mile best average of 24.6 mpg).I have not towed yet. I find it amazing that a truck of this size and power is so economical. I'm glad I bought a second one
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