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Old 12-30-2018, 03:59 PM   #393
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1992 29' Excella
2010 22' Interstate
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Originally Posted by Steve Bryant View Post
Lucius & Danielle,
You've made a good choice. I think that you'll love the truck and I will do a great job with your Airstream. Post pictures once you take delivery!

Happy New Year!
We're looking forward to this new vehicle. We'll be selling our 2005 K2500 Suburban, 8.1L in a month or two.

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Originally Posted by subfan1 View Post
Donít forget the up to 10k in rebates going on right now.
Leading up to Black Friday I was lured in by the incentives... only to find many of the incentives don't apply to me/us. In the end, with the dealer discount and the incentives that do apply, we're getting 18% off MSRP and the dealer is not adding any "packages" such as paint protection or fabric guard. In addition, they have a very modest $149 documentation fee and $14 title fee.

We'll post pictures next week.
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Lucius and Danielle
1992 29' Excella Classic
2005 Chevrolet Suburban K2500 8.1L
2018 GMC Sierra K1500 SLT, 6.2L, Max Trailering
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...
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Old 12-31-2018, 06:19 AM   #394
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2015 27' Flying Cloud
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OP here: Just completed our second cross-country and back lap on December 23. Now, about 82,000 miles on the truck. Engine is fine: towing fuel economy ranges between 11 and about 13.4 mpg pulling our FC 27 at 60 mph. Oil consumption still normal (i.e. Zero between changes). Interestingly, what really kills gas mileage is a good strong headwind or even crosswind, by as much as 2 mpg. If thereís one weak spot itís the 8-speed transmission which has an overly aggressive torque converter lock-up. Sometimes will lock up so hard when towing, just after you get moving that it feels like thereís slack in the hitch. Fortunately, GM has ditched that transmission in favor of the 10-speed, so new buyers shouldnít be concerned. If I were buying this truck used, I would be a bit concerned about long term durability of the transmission. It works fine 90 percent of the time, but displays this odd lock up behavior randomly the rest of the time, even when not towing.
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Old 01-10-2019, 03:59 PM   #395
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Okay, we purchased the 2018 Sierra, 4X4, Crew Cab, short bed, SLT, 6.2L, Max Trailering truck. I found a very inexpensive one-way ticket on Frontier Airlines and then drove the truck 3/4 of the way across the country back to our house. So I have many, many miles in the seat - mostly at highway speeds and some city traffic.

The 8-speed transmission does seem a bit quirky at very low speed - both accelerating and decelerating. I can imagine the clunkiness may be exacerbated when towing.

What felt like a tight-feeling, well-tuned suspension during test drives is proving to be a relatively rough ride - particularly when encountering potholes and the bump-bump-bump of some concrete interstate freeways. This ride of this truck is much more truck-like than either the 1996 C2500 Suburban or the 2005 K2500 Suburban we have. The Suburban's ride like Lincoln Continentals compared to this truck. I'm not saying that's entirely bad but it sure is a change from what we're accustomed.

I wonder if some of the rough/firm ride stems from the large diameter (20") rims with relatively low-profile tires? The profile on these tires results in a side wall that is about 4". The side wall of the tires on our Suburban's is approximately 6". The pressure in the Sierra tires is 35 psi or so while the Suburban is 50 front and 80 rear. Any thoughts on this? Has anyone changed to 18" tires to obtain increased side wall?

The torque and horsepower of the 6.2L engine is absolutely amazing! I've never owned a vehicle with this amount of power. I haven't had the need to "floor it" and I'd be afraid to do so because I think the tires would break loose.

We are looking forward to towing with this truck and enjoying many happy miles on the road. I hope it serves us well.

I know, I know... I promised pictures. I'll get to that later.

on edit: I put fuel in the vehicle 6 times - sometimes as little as 1/2 a tank but I did it based on wind conditions, highway speeds, terrain, etc. The best mileage was 21.9 and the worst was 17.7. These are calculated values (actual gallons put into the tank / miles on the trip odometer) as I'm not certain I can trust (or understand) how some of the information on the Driver Information Center is displayed and calculated.
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Lucius and Danielle
1992 29' Excella Classic
2005 Chevrolet Suburban K2500 8.1L
2018 GMC Sierra K1500 SLT, 6.2L, Max Trailering
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...
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Old 01-10-2019, 06:51 PM   #396
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Quote:
Originally Posted by nvestysly View Post
Okay, we purchased the 2018 Sierra, 4X4, Crew Cab, short bed, SLT, 6.2L, Max Trailering truck. I found a very inexpensive one-way ticket on Frontier Airlines and then drove the truck 3/4 of the way across the country back to our house. So I have many, many miles in the seat - mostly at highway speeds and some city traffic.

The 8-speed transmission does seem a bit quirky at very low speed - both accelerating and decelerating. I can imagine the clunkiness may be exacerbated when towing.

What felt like a tight-feeling, well-tuned suspension during test drives is proving to be a relatively rough ride - particularly when encountering potholes and the bump-bump-bump of some concrete interstate freeways. This ride of this truck is much more truck-like than either the 1996 C2500 Suburban or the 2005 K2500 Suburban we have. The Suburban's ride like Lincoln Continentals compared to this truck. I'm not saying that's entirely bad but it sure is a change from what we're accustomed.

I wonder if some of the rough/firm ride stems from the large diameter (20") rims with relatively low-profile tires? The profile on these tires results in a side wall that is about 4". The side wall of the tires on our Suburban's is approximately 6". The pressure in the Sierra tires is 35 psi or so while the Suburban is 50 front and 80 rear. Any thoughts on this? Has anyone changed to 18" tires to obtain increased side wall?

The torque and horsepower of the 6.2L engine is absolutely amazing! I've never owned a vehicle with this amount of power. I haven't had the need to "floor it" and I'd be afraid to do so because I think the tires would break loose.

We are looking forward to towing with this truck and enjoying many happy miles on the road. I hope it serves us well.

I know, I know... I promised pictures. I'll get to that later.

on edit: I put fuel in the vehicle 6 times - sometimes as little as 1/2 a tank but I did it based on wind conditions, highway speeds, terrain, etc. The best mileage was 21.9 and the worst was 17.7. These are calculated values (actual gallons put into the tank / miles on the trip odometer) as I'm not certain I can trust (or understand) how some of the information on the Driver Information Center is displayed and calculated.


I have a 2017 version. The transmission is clunky at low speeds when not towing, but no problems at all when towing my 2018 FC30. I towed about 15,000 miles last year and truck now has about 23,000 miles on it.
I averaged 12.3 towing miles from Vermont to Albuquerque and back. The best mileage I ever got was 24.6 not towing.
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Old 01-10-2019, 07:49 PM   #397
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We have an 18 GMC Sierra Denali with the 6.2l 8 spd 2 WD The transmission does have its quirks but we were told to drive it and put some miles on it which we have. Works somewhat better. I have taken it in for software updates and it is working much better. I was told GM will be out with a major software update for the transmission in January. I will be taking our truck in for the update next month.
Truck has plenty of power and tows great. The Denali has the Mag tech suspension system and it rides pretty nice compared to our 2500 Suburban we used to have. We also have the 20 inch wheel tire combination.
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Old 02-02-2019, 07:13 AM   #398
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1992 29' Excella
2010 22' Interstate
Van By The River , Georgia
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Modifications for Bypassing ITBC

I suspected the factory Integrated Trailer Brake Controller in our 2018 Sierra wasn't going to work with the electric/hydraulic brakes on our Airstream. Our initial hitch-up to the trailer proved that hunch to be correct. So... I installed an aftermarket trailer brake controller. You can read about that HERE.

Subsequent to the aftermarket trailer brake controller installation we've only towed the trailer about 50 miles to verify brakes, hitch, etc. The route did include some significant hills. So far, so good. The transmission worked well and the trans temperature remained less than 190F - a little higher than I expected but not bad. Our first trip with the new tow vehicle will likely be in March/April time frame.
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Lucius and Danielle
1992 29' Excella Classic
2005 Chevrolet Suburban K2500 8.1L
2018 GMC Sierra K1500 SLT, 6.2L, Max Trailering
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...
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Old 03-03-2019, 06:23 PM   #399
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1992 29' Excella
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Van By The River , Georgia
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After towing our 1992, 29 ft. Classic over 1000 miles Iím not quite sure what to think about this truck. The engine has plenty of power, the transmission works well on the highway but is quirky at low speeds and stop & go, and the shocks are VERY MUCH underdamped.

I cringe to think of swapping out shocks on a brand new truck. My first pass at dialing in the WD hitch may be off and perhaps thatís affecting what is perceived as underdamped suspension. Iíll certainly give the hitch more consideration before I call Bilstein.

The vehicle is reasonably comfortable and we like the fact that The infotainment system works with Apple Carplay.
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Lucius and Danielle
1992 29' Excella Classic
2005 Chevrolet Suburban K2500 8.1L
2018 GMC Sierra K1500 SLT, 6.2L, Max Trailering
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...
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Old 03-04-2019, 05:01 AM   #400
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2018 30' Flying Cloud
South Hero , Vermont
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Quote:
Originally Posted by nvestysly View Post
After towing our 1992, 29 ft. Classic over 1000 miles Iím not quite sure what to think about this truck. The engine has plenty of power, the transmission works well on the highway but is quirky at low speeds and stop & go, and the shocks are VERY MUCH underdamped.

I cringe to think of swapping out shocks on a brand new truck. My first pass at dialing in the WD hitch may be off and perhaps thatís affecting what is perceived as underdamped suspension. Iíll certainly give the hitch more consideration before I call Bilstein.

The vehicle is reasonably comfortable and we like the fact that The infotainment system works with Apple Carplay.

My thoughts, too. The transmission is fine towing, but was jerky coming to a slow stop. I took it back to the dealer and they replaced a solenoid. It's not perfect, but better. After towing about 15,000 miles, it seemed to porpoise a lot, so I decided to replace the shocks with Bilsteins all around. Non towing, I don't see much difference. I'll be picking up my 2018 FC 30RBT on Thursday for a 2 week trip with the new shocks. I'll report back if I notice a better experience towing.
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Old 03-05-2019, 06:26 AM   #401
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2015 27' Flying Cloud
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OP here. Now having 84,000 miles on this truck about 50,000 of which are pulling my Airstream, this is my experience: (1) porpoising. When I first got my rig and was dialing in the amount of tension on my w/d hitch, I experienced the same effect. The solution was more w/d tension (not a whole lot, just a little). I have a ProPride hitch using ď1,400 lb.Ē bars. Itís probably getting near time to replace the shocks. Assuming Bilstein makes a fitment for the max trailer tow package (which, as a minimum, includes different rear springs and axle), Iíll probably go for them as opposed to OEM. (2) As I have said before, the 8-speed is a little problematic at very low speeds. There have been several reflashes of the controller and after our last X-country and back a few months ago a super-abrupt lock-up just getting away from a dead stop, under load or not, along with a vibration at around 50 mph. A transmission flush seems to cured those recent problems. I suspect thereís a TSB about that; my dealer said to come back if the issue wasnít resolved in a few hundred miles. Newer versions of this truck have a 10-speed, so owners of those models wonít have to deal with this problem. That would be my only reservation about getting this truck as a used vehicle. I think the 10 speed started being used in 2018 models but it could have been 2017. The 8-speed is in the 2015 and 2016 models for sure. The 2014 model has the 6.2 DI engine but uses a 6-speed with ratios very poorly matched to the engine. I would avoid that year.
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Old 03-21-2019, 07:55 PM   #402
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How Do You Calculate MPG?

Modern vehicles have computer control, algorithms, fuel management, etc. Many people have reported the MPG of the 6.2L, 8-speed, max trailering truck in a variety of situations on this particular thread. The driver information center on this truck (at least our 2018) indicates average fuel mileage between fill-ups. Or you can calculate the old fashioned way - miles driven divided by the number of gallons of fuel to top off the tank.

If you have a 6.2L, 8-speed, max trailering GM truck how do you determine MPG? Have you noticed much difference between the number the truck (computer) reports and the manual method of calculating fuel economy?

I'll go ahead and tell you why I ask... The computer number is much higher than the number I calculate. For instance I filled up the tank today, after combined highway and city driving, and the computer indicated 16.6 and I calculated 14.4. It's not uncommon for my calculated number to be 2 MPG less than the computer number.

What gives? Am I doing something wrong? Am I misunderstanding what I see on the driver information center? How do your numbers compare? If you've reported MPG numbers in a previous post on this thread which numbers where they - DIC or calculated?
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Lucius and Danielle
1992 29' Excella Classic
2005 Chevrolet Suburban K2500 8.1L
2018 GMC Sierra K1500 SLT, 6.2L, Max Trailering
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...
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Old 03-22-2019, 05:19 AM   #403
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The truck does not calculate mileage between fill ups. Depending on settings, it calculates mileage over distance. The largest distance, if memory serves is 400 miles. The shortest, I believe, is 50. Itís a ďrollingĒ average, so itís always updating itself. The trip computer (there are 2) will calculate mileage for the trip. So, if you wanted to compare the a hand calculation to the truckís, you could reset a trip computer at fill up to zero. Then, the next time you fill up, you could read out the truckís calculation of mileage and compare it with your own. The problem with a hand calculation is that unless you fill up to the point where you spill fuel out of the fill pipe (not a good idea), itís just about impossible to get a consistent fill. So the hand calculation isnít going to be totally accurate. The truck calculates fuel running through the fuel system and it has to be very accurate because otherwise the engine management system would not achieve emissions targets. Both hand and truck calculations depend on the accuracy of the speedometer/odometer. If the speedometer reads a little fast (as is common with many vehicles), mileage will be overstated. On my truck, the indicated speed on the speedometer matches the speed shown on the GPS, so I assume itís accurate. By contrast, my 2008 Honda Pilot speedometer reads 1 mph faster than what is shown on the GPS.
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Old 03-22-2019, 03:03 PM   #404
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I've seen the rolling average best/worst MPG and noticed it has three or so "averaging" distances - I seem to recall 25, 50 and 400 miles but I'm not certain. Changing the distance does change the best/worst calculation shown on that screen.

The MPG I'm referring to is the Trip A parameter. I reset it every time I fill up with fuel. I've not recorded the average fuel economy shown on the Trip A screen but I know it's always been higher than my calculated MPG. Almost always 1 MPG higher and sometimes 2+ MPG higher than my calculated value. I realize filling up the tank is not a precise science but I typically go to the same gas station around town (it's pretty level) and I typically look for a relatively level area to fill-up when we're traveling.

Regardless, if I'm consistently 1 - 2 MPG different than the trip value that means I'm pumping in more gasoline than the tank can hold over time. Even with some measure of inconsistency in filling the tank it should average out. I've put fuel in this truck over 20 times and it's always more gallons than the Trip A screen would lead you to believe.

I'm not complaining about the MPG - I like the truck and its fuel economy is higher than the previous tow vehicle although with the premium fuel requirement the $$ are probably a wash.

Let me get at this issue another way... Let's consider doing a science experiment with our 6.2L, 8-speed, max trailering trucks. Consider checking your MPG the old-fashioned way: miles driven divided by gallons put into the tank and compare that to the fuel economy shown on the Trip A screen.

I'll do this for the next several tanks of fuel and report back on this thread.

P.S. I've done some preliminary validation of the speedometer and odometer using a separate GPS and the numbers correspond very well. There doesn't seem to be enough variation to account for this odd MPG variance.
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Lucius and Danielle
1992 29' Excella Classic
2005 Chevrolet Suburban K2500 8.1L
2018 GMC Sierra K1500 SLT, 6.2L, Max Trailering
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...
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Old 03-22-2019, 03:58 PM   #405
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Originally Posted by nvestysly View Post
Even with some measure of inconsistency in filling the tank it should average out. I've put fuel in this truck over 20 times and it's always more gallons than the Trip A screen would lead you to believe.
How vigorously do you fill your tank? Do you keep topping it off after the pump has automatically shut off? Modern gas pumps have a vapor recovery system with an ill-fated feature that pushes all "extra" fuel back into the pump reservoir tank. In simple terms, topping off your tank simply raises your fuel bill without any additional liquids entering your vehicle's tank. This would serve to artificially lower the value of any manual fuel efficiency calculations.
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Old 03-24-2019, 08:14 AM   #406
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The variance in fill will not make a significant difference in the calculated mpg. It is, at most, 1/4 gallon variation in a 30+ gallon tank and, as noted, it would average out over a couple of fills.
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