'22 3500HD Silverado LT CC/SB L8T First long 5th wheel travel trailer tow

sheath · April 5, 2022

Seems quite a few people consider using a gas engine to pull big 5th wheel travel trailers. Thought I'd share my experience on the first pull.

The short of my opinion is: It is not a pleasant experience when compared to a diesel engine. That wrote, based on my use the L8T was the best choice. It may be for you too.

I pull a bit less than 30% of the time. Usually that is one to two days when moving to a new area, then park the 5th wheel from two weeks to a few months. The rest of the time is short trips on a daily basis. Short runs on diesel engines are really hard on the truck. I've been at RV parks where guys are doing forced regen's because of this type operation.

Pulled the 5th wheel from North Bend, OR down the coast highway 101, and across from Petaluma to to the Central Valley in California. There are quite a few 6%-ish grades along the route, I noticed one summit at just over 1,500', and there was a larger grade through the coastal range. Temps were in the mid 50s. The 5th wheel weighs 14,300 lbs currently, and is a wide body (100") which is a big frontal area.

Average fuel consumption on the first tank (through most the mountain grades) was just over 7.5mpg. Once things leveled out, the fuel mileage went up to a bit more than 8.5 mpg. Most of this was at about 55 mph.

So this brings up the first issue. As much as possible I use cruise control. But that was problematic on the mountain climbs, and on some of the down hills. On the uphills, it would downshift, and rev out to over 5K rpms to try and maintain speed. I am not comfortable pushing an engine that hard. So I stopped using cruise and just let the speed drop down in the 40-45mph range to keep rpms down between 3,200-4,500 rpms. That made me "feel better". But the power below 3,500 rpm feels weak, and it seems the engine doesn't like to work in that range.

On the down hills, it would "grade shift" in spots I'd have rather the rig just coasted, because of the upcoming rise. So I didn't use it much on the downhills either. Not sure if more gears (i.e. 10 speed) would help here, because this engine seems to like the higher rpms to make power). But I would like to try one with an eight or ten speed, if GM decides to build that combo. The engine "felt" best between 3,500, and 4,200 rpms.

In comparison to my old Dodge with the 5.9L, four speed auto and Pacbrake, I pretty much lived on cruise control. The diesel having the torque to handle grades much better. I can only imagine how much better the new diesel trucks with almost 1,000 lbs/ft of torque would be pulling this same trailer.

The second issue is due to the short bed truck having the hitch ball 2" behind the rear axle. This un-weights the front end, and the truck "floats" down the road. Steering input is imprecise, and loose feeling.

Edit to add: I may have created this issue by choosing the Snow Plow/Camper Option (YVU) That option steps up the front torsion bars to the highest rating.

Current pin weight is about 60lbs under max allowed. I'm going to add a chest at the front of the bed, and put some heavy gear in it. I'm also putting a front hitch on the truck, and for now it will hold a motorcycle carrier and an 80 lbs e-bike. That 150-ish pounds in front of the bumper should help load the front end back down.

Highway 101 is a mess, there were sections going down the coast that was cut down to one lane with stop lights to control traffic. Pulling the wide trailer through some of those switch-backs with cement barriers on one side, and cones on the other was exciting... lol Overall, while a bit stressful due to the front end of the truck being a huge block, I was impressed with how precisely I could navigate difficult slow speed maneuvers. I pulled into a gas station in Eureka, and immediately thought "Uh-oh!" The entrance was wide, the overhead clearance was generous. The exit was made for mini-cars.

When I pulled out, everyone at the pumps, and the employees came out to watch. In that situation, the truck was a champ. I was able to wiggle out in a single shot going forward with less than an inch to spare on any corner. Everyone applauded as I hit the street... roflol Truth is, I'm not sure I'd have made it out, if I'd had to back up at any point.

I'm now very comfortable where each corner of the truck, and trailer is.

Third issue is the poorly functioning trailer electronics. I programmed in the trailer, set the brake bias, shifted into Tow Haul Mode and got about 1/10 of mile down the road before the DIC started swapping back and forth between "disconnected trailer" and "Check Tow Haul mode." To resolve that stupidity, I pulled over, shut off the truck, unplugged the trailer, waited a few minutes. Then I plugged the trailer back in, started the truck, turned on Tow Haul mode, and used "Generic Trailer". It seemed to think that was OK. Reset the brake gain, and headed down the road. No more issues as long as I used Generic (or Guest?) Trailer mode.

4th issue. Brakes on the truck feel spongy to begin with, so getting a balance of truck to trailer brakes under light braking... well, I just gave up on that. Trailer ended up doing the majority of slow speed light braking.

On the positive side of things: While the steering feels light and imprecise, the truck itself feels confident stability wise. The rear of the truck doesn't move laterally, and handles the 2,400 lbs pin weight and overall 14,300 lbs trailer weight just fine. I really think once the front of the truck has some weight on it, the overall handling experience will be planted and responsive.

Mirrors work fine, with the exception that the spot mirror view is too low. But they do provide a good view of the trailer tires in turns.

I don't drive fast, rarely feel the need to pass someone and really like this truck for city/non-towing work. It is comfortable on long trips with or without the trailer. For the 70%-ish time it doesn't pull a trailer, it is an awesome truck. It pulled just fine on 87 Octane fuel, which saved money over diesel, and Ford/Dodge needing 93 to tow. I'm pleasantly surprised on the fuel mileage as well. I was only getting a bit over 11mpg with the Dodge pulling this trailer, and that would drop down to about 9.5 mpg pulling grades.

The key to me with the gas engine seems to be more about patience and good planning. The willingness to pull slower, and pick good gas stations is a must.

Hope this is helpful to someone trying to decide between the Duramax, or this L8T to pull their big travel trailers. :cheers:

Edited April 9, 2022 by sheath
edited to add in Snow Plow/Camper Option

Michael621 · April 7, 2022

Happy camping anyhow!

XY74 · April 8, 2022

I'm surprised you would notice any front end unloading with a 5'ver. I think it was TFL that went to the scales with a truck and gooseneck trailer (2500 ish pin weight?) and it only changed the front axle weight 100 lbs. I tow a bumper pull camper and it unloads the front axle a few hundred lbs, no issue to me. That said, mine is a diesel.

14,300 is a lot of trailer. Sounds like the L8T is a pretty stout engine to tow it so well as it does.

sheath · April 8, 2022

2 hours ago, XY74 said:

I'm surprised you would notice any front end unloading with a 5'ver. I think it was TFL that went to the scales with a truck and gooseneck trailer (2500 ish pin weight?) and it only changed the front axle weight 100 lbs. I tow a bumper pull camper and it unloads the front axle a few hundred lbs, no issue to me. That said, mine is a diesel.

14,300 is a lot of trailer. Sounds like the L8T is a pretty stout engine to tow it so well as it does.

I think if GM would have put the pin centered on the axle it would not unload the front end this much. This truck has halogen headlights, and I was still getting flashed by on coming traffic due to how high the front end was.

Just realized I may see more than a normal rise in front end due to having the Snow Plow/Camper option, which has the highest capacity front torsion bars. Someone without that option, may not see as much lift. I may be a victim of my own doing... roflol!

Really looking forward to the bike on the front hitch. Also I'll be able to unload about 500lbs of dead weight into the bed chest (ordered this 62x27x20 Weather Guard Bed Chest . That weight currently sits ahead of the trailer axles, in the storage bay.

Between those two weight shifts, I'm thinking it will settle right down. If those changes don't get a solid feel, I'll look into seeing about pinning an offset ball to move the trailer forward. There is plenty of room between the trailer and the C pillar.

I'm loving this truck. The L8T has a good pull. It does have a weird dip in power right about 3200 rpm, but above that it pulls good. Not sure if it is considering a shift & cutting power or what. But it happened over several of the grades. Transmission never exceeded 212*F, so it's not struggling. :thumbs:

While I'd have gone diesel if I did at least one good hour long trip per week, this combo seems to be the best decision in my case. Good fuel mileage and the least expensive fuel option is a great benefit. :cheers:

When I was able to wiggle out of that gas station with almost no room to maneuver, it put a huge smile on my face.

Went to lunch with a friend yesterday, and she commented on how nice the ride was. I still had the tires set at 60/80 psi.

Edited April 8, 2022 by sheath
realization of front spring choice

GMC4Zee · April 15, 2022

I applaud your gas decision as that was my reason also for going gas. My 5th wheel is slightly less with 12K trailer weight and about 2200 at the pin. Pulled a few of the mountains in PA and I say just let it rev. That does not hurt the engine although it does lower the gas mileage. I average about 8mpg towing but the truck seems to be getting better mileage wise around town (14mpg) unloaded. Camping season is coming up so hope to gain another .5 mpg. I have the 6.8' bed and Anderson hitch which puts the pin over the axle. I did put sumo springs on the rear leafs and it reduces squat by maybe an inch but truck looks level when hitched. Have not went to scales to verify. I do have cameras on side mirrors that help on turns when connected to trailer. Just wish GM offered a larger fuel tank. 36x8=288 miles till empty.

sheath · April 15, 2022

I really like the Andersen setup. Looks a lot easier to connect, with the ball sitting up tall.

Since the engine is built for fleet use, I'm betting you are right about allowing it to just rev out. I'm OK with dropping the speed. Most the time grades are through some beautiful country, so I just turn on the hazards and enjoy the scenery.

Happy Camping! :cheers:

f8l vnm · April 18, 2022

Next year with the 10 Speed , the new gasser should be even more stout.

sheath · April 18, 2022

Somewhere I read GM is holding off any major changes until after 2023.

I'm interested to see if they upgrade the transmission how it works out. Just finished a pull from Stockton, CA up to Sonora, CA (in the Sierra Nevada foothills). It was about a 70-ish mile climb from about 20' ASL to about 1,500' ASL. Modest inclines of 4%-6%. Climbed just fine, and this time the 5th wheel weighed in about 14,600 with a tank of fresh water. Only once did the Cruise control kick down all the way to where the engine rev'd to 5K rpms. Had a lot of traffic behind me, so just let it run, because there was no place to pull over.

Based on my limited towing time, what I would like to see is the ability to get the truck to hold a gear without downshifting further. Maybe program this into the tow-haul mode. This would help with the rolling foothills, where the road continuously goes up and down 50'-100'.

I really like the way the engine sounds and feels in that 3.500-4,200 rpm range. It feels like a good "working" range. It's like all the oscillating harmonics go away, and it is strong/happy. Can't figure out better words, so i hope this makes sense.

Another JR · April 19, 2022

2200 lbs pin weight 2 inches behind the axle unweights the front axle only about 25 lbs. When towing, the pulling force with that big 5th wheel applied at the pin height unweights the front wheels by up to around 300 lbs, and adds that same weight to the rear axle. When braking the opposite happens.

That pin weight settles the rear end a little over 2 inches (my slide-in camper is about 1800, and it settles 2 inches - does not hit overloads). Your front axle is not affected in this static condition (other than the measly 25 lbs). This rear end squat nicely “levels” the truck, the way it’s supposed to be done, but is enough that I needed to adjust the headlights down. I just leave them that way. It’s very easy to adjust them. You just need a long 5 mm hex wrench and a good location to see the light pattern.

Edited April 19, 2022 by Another JR

sheath · April 19, 2022

Adjusting the headlights for the trailer load is a good idea. I'll bet once I figure out how many turns of the adjuster gets it set, I can "reset" really quick. Thanks! :cheers:

At 2,400lbs pin weight, the overloads are touching the pads. The light feeling is more about rough undulating surfaces where the suspension on truck and trailer is compressing/decompressing front to rear and side to side. Will be fun to see the difference in feel when the bike is up front, and the 500-ish lbs are loaded into the bedbox.

Another JR · April 19, 2022

Yes, that feeling of having a stiff, lightly loaded front axle that rebounds quickly and a loaded rear axle that rebounds slowly does not feel good, and causes the front to feel like it’s bouncing too high sometimes. It’s just a wrong suspension tuning. I like the response of the axles to be the same, or the rear to be stiffer. It’s just what I’m used to and provides a better feeling of control.

I have that effect, although to a lesser degree, on my truck with the 1800 lb slide in camper installed (1700 lbs on rear axle and 100 on front axle) combined with having the 5600 lb “heavy duty camper springs” in the front. (When the truck is empty the front and rear axle response is pretty well matched with the camper springs - they’re BOTH too stiff.). That’s why I’m installing the base 5200 lb springs - to have better matched axle response when the camper is on. A softer ride will be a bonus. My new torsion bars just arrived today, so I may do the swap this weekend.

GMC4Zee · May 13, 2022

Another JR, what is the cost of the lighter front springs? Would it help to turn the torsion keys some to lower the front end without the swap? I have Sumo springs on the rear in place of the bump stops. This limits the squat by about 1/2 inch when hooked to 5th wheel.

Another JR · May 13, 2022

I recently posted a detailed thread in the mod forum on the torsion spring swap in case you are interested.

The new front springs are $200 to 220 each on line, but shipping is a bit over $100 for two. The price was comparable ordered from my local dealer’s part department, and it was more convenient for me to pick them up from the dealer. I saved forum member MTU’s table of spring part numbers and had my dealer verify it before I ordered. I can post the table again if you need it.

The swap took me 2.5 hours, but I had not jacked the truck up previously and a bunch of that time was spent figuring out how I wanted to jack and support it. I could do the job again in less than 90 minutes. Unlike the older trucks, the spring ends have a looser fit and won’t be stuck in place. Mine came right out.

Adjusting the torsion keys doesn’t change the spring rate or ride stiffness - it just changes the front suspension height. I set mine to the exact same height as the original springs.

Another JR · May 13, 2022

3 hours ago, GMC4Zee said:

Another JR, what is the cost of the lighter front springs? Would it help to turn the torsion keys some to lower the front end without the swap? I have Sumo springs on the rear in place of the bump stops. This limits the squat by about 1/2 inch when hooked to 5th wheel.

I should have quoted you above so you’d get notification of the response.

sheath · May 13, 2022

I've had a few good pulls over the past month.

Went from Lodi, CA to Oakhurst, CA via highway 4 & 49. Highway 4 is a highly traveled road, and is pretty easy to maintain the 55mph speed limit. Climb is from about 50'ASL to about 2,200' ASL. I don't remember a grade more than 6%. Was able to control downshifts by adjusting speed to keep the engine in that 3,500-4,200 rpm range that I like. Felt very comfortable for me. I tend to tow slower than most, and have no problem moving over, or using the pull outs to let people pass, so I don't get shot... lol

Highway 49 is a different animal completely. It is narrow and winding, climbing around and over ridgelines of the foothills for the Sierra Nevada mountains. CALDOT shows it as a truck route but there are sections not recommended for rigs longer than 30' King Pin to trail Axle. I'm about 25' KP to rear axle, but at 100" plus awnings it's a bit large, and uncomfortable on this route. Glad I did it, won't do it again.

The big thing about 49 is the slow speeds, and tight steep grades with blind turns, and drop offs. So, the Torque converter never gets a chance to lockup. I saw a max trans temp of 232*F, even though the climbs continued the temp never went above that. That is an OK temp, as far as the fluid is concerned, but I'd still like to see temps not exceed that 210-ish* range for longevity of solenoids, internal harness, etc..

Overall about 142 miles of tough towing. Fuel mileage was about 7 mpg (there was a lot of running around without the trailer, so this is within about 1/2mpg). Because the speeds were slow, there were only a few downgrades where an exhaust brake would have been really helpful.

The trip from Oakhurst to Bryce Canyon City, was easy. A few long climbs (The climb out of Bakersfield, The climb from Baker up to the plateau, the climb up to St. George, and the big climb up to Bryce Canyon). Had a pretty good tail wind, which increased fuel mileage to over 8.5 mpg. Which is pretty good considering the trip started at about 2,200', dropped to 500' and then went up to over 8,000' elevation. The toughest part of the drive was going past Ft. Irwin. I still get a twitch thinking back to the 30 days spent training there... lol

The pull from Baker to the summit is long and relentless. There is a sign on the freeway to turn off AC. I didn't need to. Truck ran fine at 55 mph for the most part. There was steep section where I let the speed drop so the downshift would peak the rpms at about 3,800 rpm. I was still passing big rigs.

Had a few big gusts hit the truck/trailer from the side. Pretty sure the sway control engaged, and I was able to stay within the lane. That is very confidence inspiring.

Coming down the 8% grade through Bryce Canyon NP to Bryce Canyon City could really benefit from the diesel with exhaust brake. Thankfully it is a short distance before the grade lowers to about 4-5%.

Overall, this was a great opportunity in getting to know how the truck performs towing in extreme, and reasonable environments. I'm happy with the performance, and confident it was the right decision for my use.

Spending $200 and not getting a full tank of gas was a bit disturbing... Glad to be out of California.

Date	Mileage	Fuel / Maintenance	Maintenance Type	Cost	Mileage	Notes
05/06/22	3509	Fuel	Partial fill 23.325gls	$125.00	N/A	Driving around Angels camp and trailer pull to Coarsegold via 49 slow speed hilly & winding
05/08/22	3551	Fuel	Final fill 9.831gls	$52.68	9.96	Driving around Coarsegold/Oakhurst and trailer pull as per G16
05/09/22	3847	Fuel	Partial fill 30.308gls	$200.00	N/A	Pull from Oakhurst to Ft. Irwin, CA. $6.60/gal... Aaack! Pretty steady 55mph on cruise
05/10/22	4018	Fuel	Final fill 20.061gls	$100.28	9.27	Pull from Ft. Irwin, CA to Lost Wages, NV Pretty steady 55mph on cruise with a bit of a tail wind
05/10/22	4224	Fuel		$121.29	8.15	Pull from Las Vegas, NV to Panquich, UT. Good climb from about 2K' to 6K' at about 62mph mostly on cruise with a tail wind