Report on Chevy/GMC 1500 with 6.2 engine and Max tow pack

[r carl]

I think its the computer too.

[Steve Bryant]

I have driven my truck now for about 3 weeks. For the most part, the shifts up and down are silky smooth. Occasionally there will be a bit of a clumk on the first or second shift of the day.

I've done a little research and it appears that what causes some of this clunky shifting with the 8L90 transmission at very light acceleration is when it's time for the transmission computer to shift up and simultaneously the engine is switching from the V8 mode to the V4 mode with cylinder deactivation. There can be some kind of mismatch and yes it is a computer issue. But for the most part it's excellent transmission. Probably the best that I've ever had in a vehicle.

[DC Bruce]

OP here. I now have 51k miles on my truck. The 8-speed has a very aggressive torque converter lock up program. So, under very light acceleration-or if you coast and then accelerate very gently- you can get that abrupt lock up that makes a clunk at speeds under 25 mph. Accelerating more normally or towing in tow haul mode, you don't get it. Actually very smooth shifting up and down. As they say, "YMMV," but you will get significantly worse mileage with the 6.0, as compared to the 6.2. The 3/4 truck itself is heavier than the 1/2 ton and the engine doesn't have all of the fuel-saving features. Premium fuel is recommended for the 6.2, but I have been using mid-grade for non-towing use with no issues. Still get 22-23 mpg on highway not towing. I'm sure you can form your own opinion from a test drive, but the 6.0 seemed seriously underpowered to me, which equals a lot of noise when towing. If I ha needed the extra capacity of a 3/4 ton, I would have gone with the Ram 6.4 or the Ford 6.2 (assuming I didn't want to pay the extra cost of diesel). I met a guy in SoCal with a new FC27 like mine that he was pulling with a new Ram 6.4 and he was very happy with his choice.

[lsbrodsky]

DC Bruce,

What are you seeing for towing mileage? Are you at all bothered by the size of the gas tank in a GM 1/2 ton compared with the ability to get a much bigger tank in the Ford 1/2 ton?

Larry

[gypsydad]

Originally Posted by lsbrodsky

DC Bruce,

What are you seeing for towing mileage? Are you at all bothered by the size of the gas tank in a GM 1/2 ton compared with the ability to get a much bigger tank in the Ford 1/2 ton?

Larry

Great questions; I am watching for the answer....I liked the ride, power, and idea of the GM 6.2, 8.speed and I am comparing to the F150 10speed EB Lariat with HDtow and 36 gal tank; this type data is great for all of us looking for new TV...

[dznf0g]

For me, the exception on the low end is 10 mpg. The exception on the high end is 14mpg. The norm and a good average expectation is 12 to 12.4mpg. That's towing a 9000 lb, 30' Classic.

[lsbrodsky]

Same mileage as the 5.3 essentially, which is a good thing. It is just hard to swallow that GM will not match Ford in the range capability with a larger tank in an LTZ 1/2 ton. I wonder if they lose some sales as a result. If I had ten extra gallon of tank, I would never need to carry a plastic jug.
Larry

[DC Bruce]

I think the best I've done over 400 miles is 13.8. Worst is about 11. That's towing 7600 GVW FC 27. My towing speed is 62 or posted limit, whichever is lower. Yes, in previous comments, I've said it would be nice to have more fuel capacity and range. That said, the only time it was a serious issue was when I rolled into Tonopah Nevada with about 1.5 gallons left in the tank after having been on a very remote highway with no services for a long time. I do carry about 3 gallons for the generator in the bed. Honestly, I don't think it's an issue in the lower 48; you just fill when the gauge says 1/2. Understand that, with the Ford, that 36 gallon tank comes straight out of payload. As I recall, if you want a crew cab, the Laramie or higher trim level and the big tank, you can't get the max payload package. Of course, the 3/4 tons all have bigger tanks and bigger payloads. However, from what I've heard, the gasoline powered models will get 2-3 mpg less because of the heavier vehicle. So i don't know if you'll net more range or not. With the diesels, you'll get about the same fuel burn as I'm getting so that will net you more range with the larger 3/4 tank. Plus the lower volatility of diesel makes an add-on tank more feasible and safe. I'm thinking about an Alaska trip this summer and have calculated that I could carry 2 metal 5-gallon JERRY cans full of gas and still be within weight. They are not cheap, however.

[dznf0g]

Originally Posted by dznf0g

For me, the exception on the low end is 10 mpg. The exception on the high end is 14mpg. The norm and a good average expectation is 12 to 12.4mpg. That's towing a 9000 lb, 30' Classic.

I should have added, I drive 65 on interstate and 60 on 2 lanes, when possible.

[lsbrodsky]

The thing about fuel capacity is that I do not like looking for acceptable gas stations enroute to my destination. I like to fill up once per day, at my destination or before I get going. Since I prefer driving about 250 miles per day this usually works out fine with my 26 gallon tank. However, I usually carry a small plastic fuel jug, just in case. We do stop along the way, but in parking lots, rest areas, whatever.
A 36 gallon tank would be a guarantee, for me, that I would never need to add fuel before I get to my destination. The weight of 10 gallons of fuel is a non-event for what I carry in the bed. Stupid as it may be, when I need to replace this truck, I will look seriously at the Ford Supercab Lariat simply because of the larger tank. Sad for a die hard GM guy.
On the other hand, by the time I do replace this truck both products will have changed and if GM no longer has a big naturally-aspirated engine, my GM loyalty will evaporate.
Larry

[Steve Bryant]

Originally Posted by cliffcharb

Well I went looked at a couple different models this week. Trying to decide between the max tow or the 2500 HD Denali 6.0l. Currently in my area both of these vehicles are priced the same, around $52,000. One thing I noticed and didn't like on the max tow was the clunkiness of the transmission. The salesman told me that was typical of the 8 speed. I'd like to ask those that own this truck if that is indeed normal.

Cliff,
I've carefully observed the shifting of my transmission for the past two days and there hasn't been one misstep! So at least in my experience, I have nothing for praise for the transmission and the vehicle in every way.

Steve

[dznf0g]

Originally Posted by fullahotair

My 8 speed can be rather clunky at times. What i would say is that there is a small learning curve on how to drive it to avoid the clunking. I found if you "get up and go" from a stop, it works beautifully. I am not talking about mashing the pedal from a stop, but something slightly more than an old man drive style where you try to see how long you can stay in any given gear. I found the 8 spd likes to shift, so I let it. The 8 spd clunks when it isn't sure if you are going to want it to upshift or down shift - and as a result it sometimes makes a bad decision which results in a clunk.... I find i am most apt to get a clunk putz around in a gear.

My dad has a 6.2/8 spd denali, but his doesn't clunk like mine, but i suspect that might be due to the different gearing his has.

I have made a study of the shifting of this trans and have inquired internally about it. Here's what I have found.

1) when brand new, there is an initial "learn" programmed into the trans for distribution. That is, as the truck is moved around the plant yard, onto and off transporters and trains and around dealer lots, it remains in the "factory learn". It take upwards of 1000 miles for the truck to learn your driving habits and move out of the factory load. That seems like a much higher learn time than I was used to in other transmissions, but it is what I noted by the seat of my pants. Also, the same is true for TH mode, but it seemed to be much shorter in duration...maybe because I had driven (not towing) for most of the learn process.

2) Driver habits: I have always used my throttle foot to get earlier shifts by lifting my foot when I want the next upshift. You can't do that with 8, 9 and 10 speeds. It is too hard to predict the quick shifting, from first to second and so on, under normal acceleration and you always miss the exact shift point. This also confuses the transmission control module learn process, potentially. It is best to use a smooth application of the throttle and let it do it's thing. This is a driver re-learn process.

3) There is a different shift routine with a cold trans. If you watch the transmission temp screen, you will notice a marked difference once you cross the 90* F fluid temp. This is to better regulate the shifting sequence and protect the trans with cold fluid.

4) I do agree with the comment about the possibility of a shift at the same time, or close to a move from 4 to 8 cylinders and vice-versa. I have reported this for a possible software change, which would prohibit the two functions from happening close together. It's not a mechanical problem, but is a customer irritant.

Edit: I just went in and checked. The new calibration has been released.

" Bulletin#16-NA-411: Harsh 1-2, Harsh 3-1 Decel Downshift, Harsh Downshifts Under Heavy Throttle, AFM Transition and Step In Clunk During Downshift - (Jan 20, 2017)" I'll get it done during my next free LOF.

[Steve Bryant]

I've driven my truck a bit over two months now and in general it's fantastic on all counts:

• Fit and Finish - excellent
• Ride and handling - excellent (wish the shock damping were a little more controlled...especially towing...might install Bilstein 4600 shocks/struts sometime
• Powertrain - Superior (engine, light to moderate throttle...smooth as silk, wide open throttle solo...hold on tight; transmission - silky smooth shifts 99.5% of time, occasional mild clunk under very light throttle)
• Instrumentation - Excellent
• Instrument Lighting - Excellent
• Interior Lighting - Good (they should have added an LED Dome Light, Front reading lights should have been aimed little aft and a bit more outboard for effectiveness)
• Exterior Lighting - Excellent (I have the LED projector beams and they are slightly better than the HID projectors in my 2013 Jeep Grand Cherokee. These headlamps are a huge step forward like Halogen bulbs a generation back)
• Towing:

• Trailering Mirrors - Excellent Aft Vision (forward vision at 10:00 and 2:00 blocked somewhat, but is to be expected)
• Trailer Brake Controller - Industry Benchmark Good in my opinion

I realize that I'm not completely objective, but that's how I'm feeling. The only shortcoming that I see is I wish the truck had a 7,800 GVW and 4,500 Rear Axle. It needs a little more payload margin if the tow rating is as high as it is.

[Pat Cassity]

Steve, if you don't mind, what is the payload capacity of your vehicle based on the door sticker? Thanks, Pat

[dznf0g]

Originally Posted by Steve Bryant

Food for thought - I wouldn't remove the rear seat unless I really needed the cab volume that would be freed-up. The rear seat is about on the truck's center of gravity so about half of the weight is on the front axle and half is on the rear axle. So if the seat weighs about 80 pounds, that would only remove about 40 pounds off of the rear axle. When towing, even with a properly adjusted weight distribution hitch, the front end will be somewhat lighter than the rear and 40 pounds wont make much difference. The same is true for the rear axle. Even if you're at or a tiny bit above the max rear axle weight, removing the rear seat won't really help very much. Also, when the occasion arises that you do want to offer someone a ride in the back seat, it won't be there when you want it. This is just my two cents!

Steve

That's all true, but it's more about space and overall weight. Again, this would only be when we start extended travelling after retirement in a year or two. When we go for months at a time, I will want to bring all the toys, including the Inflatable SIB and 10hp motor, and all its paraphernalia, as well as the scooter, both gennies, etc. The seat consumes roughly 12 cubic feet of volume.

[Steve Bryant]

Originally Posted by Pat Cassity

Steve, if you don't mind, what is the payload capacity of your vehicle based on the door sticker? Thanks, Pat

Pat,
My post number 232 in this thread has that information. Now, my truck is a pretty fully-equipped version of these vehicles (4X4 and SLT Crrew Cab Premium Plus Package although it does not have everything that you can order like a sunroof, rear entertainment, etc.) so it looses some payload.

[Steve Bryant]

Originally Posted by dznf0g

That's all true, but it's more about space and overall weight. Again, this would only be when we start extended travelling after retirement in a year or two. When we go for months at a time, I will want to bring all the toys, including the Inflatable SIB and 10hp motor, and all its paraphernalia, as well as the scooter, both gennies, etc. The seat consumes roughly 12 cubic feet of volume.

I see your point!

[gypsydad]

Thanks Steve; your review is appreciated! I am leaning hard to the F150 again for my next TV. I think either the GM or the Ford is a great choice, but I do enjoy the 36 gallon tank, step in the tailgate, and the new engine/trany in the F150 EB. Will be interesting to see how these review end of the year!

[Pat Cassity]

Originally Posted by Steve Bryant

Pat,

My post number 232 in this thread has that information. Now, my truck is a pretty fully-equipped version of these vehicles (4X4 and SLT Crrew Cab Premium Plus Package although it does not have everything that you can order like a sunroof, rear entertainment, etc.) so it looses some payload.

Yep, I see that. A little disappointing as I was hoping that the 17s had a little payload boost. My 15 similarly loaded is 1950. Not much of a difference. Still a great tow vehicle and I am sure that the 6.2 engine and 8 speed transmission is great upgrade!

[Steve Bryant]

Today, with the help of my trusty friend, Ralph, we washed the trailer...a task long overdue. Then we went to a local truck stop with nice/accurate electronic scales and weighed the combo of the new Sierra with the trailer and the Sierra alone. Then we went to a public park and took a few pictures in the parking lot (one posted below). Also, I made a chart in Excel showing the weights of the trailer and the half ton Sierra plus the K2500 Yukon XL that we owned for seventeen years (also see below).