Towing with new 6.4L

[swampwater]

Thanks for this thread. I have been thinking of ditching my 16 with 6speed moving up to a 19+ with the 8speed for better towing mpg. But it looks like the towing mpg is about the same. I get ~9mpg pulling my 32ft enclosed with several atvs (~9000) and about 7-7.5mpg pulling our 24ft Boy Scout trailer that weighs about 12k with all their summer camp gear in there. Both at ~70mph, but the scout trailer is getting pulled through more hilly/mountain terrain (CO, NE, etc.) and the atvs stay mostly in TX and LA

 

[Firebird]

Thanks for this thread. I have been thinking of ditching my 16 with 6speed moving up to a 19+ with the 8speed for better towing mpg. But it looks like the towing mpg is about the same. I get ~9mpg pulling my 32ft enclosed with several atvs (~9000) and about 7-7.5mpg pulling our 24ft Boy Scout trailer that weighs about 12k with all their summer camp gear in there. Both at ~70mph, but the scout trailer is getting pulled through more hilly/mountain terrain (CO, NE, etc.) and the atvs stay mostly in TX and LA

My current truck with 4.10 gears and 8 speed gets the same as my 2018 with 3.73 and 6 speed

 

[jdefoe0424]

Thanks for this thread. I have been thinking of ditching my 16 with 6speed moving up to a 19+ with the 8speed for better towing mpg. But it looks like the towing mpg is about the same. I get ~9mpg pulling my 32ft enclosed with several atvs (~9000) and about 7-7.5mpg pulling our 24ft Boy Scout trailer that weighs about 12k with all their summer camp gear in there. Both at ~70mph, but the scout trailer is getting pulled through more hilly/mountain terrain (CO, NE, etc.) and the atvs stay mostly in TX and LA

You might get the same mileage, but I bet the overall experience will be better. Especially on grades, there's mores gears and thus better spacing so you aren't screaming to maintain speed because the next gear is too far and the RPM's fall out of the powerband. Another reason I went with the 8 speed is to stay away from the 66rfe and it's ticking time bomb tendencies.
If you're curious, you can try renting a newer truck and see how it handles the trailers.

 

[Firebird]

You might get the same mileage, but I bet the overall experience will be better. Especially on grades, there's mores gears and thus better spacing so you aren't screaming to maintain speed because the next gear is too far and the RPM's fall out of the powerband. Another reason I went with the 8 speed is to stay away from the 66rfe and it's ticking time bomb tendencies.
If you're curious, you can try renting a newer truck and see how it handles the trailers.

Yes, the drivability is light years better with the 8 speed!!

 

[Flyfingers]

Can anyone chime in on RPM's at say 65 mph with both 3.73 and 4.10's? Curious as to what the difference is at highway speeds.

 

[Rockcrawlindude]

Can anyone chime in on RPM's at say 65 mph with both 3.73 and 4.10's? Curious as to what the difference is at highway speeds.

Only a 10% difference at all speeds but here is a tool

Spicer Transmission Ratio RPM Calculator

Use the Spicer Transmission Ratio RPM Calculator to determine your engine’s RPM based on the transmission gear ratio, tire height, MPH, and ring and pinion gear ratio.

spicerparts.com

 

[RAM_Dad]

And at 70 mph, you're most likely in 8th unless towing. 8th is a .67:1 ratio I believe.
Roughly 200 RPM difference.

 

[kxnate]

2nd tow today with my 2021 6.4l. Enclosed v nose car trailer with 2 RZR side by sides in it so probably about 7000lbs ish. Towed 170 miles, cruise set at 65mph the whole time. 8.7mpg......meh not great. Pulls fantastic but fuel mileage sucks!

 

[Flyfingers]

And at 70 mph, you're most likely in 8th unless towing. 8th is a .67:1 ratio I believe.
Roughly 200 RPM difference.

OK that makes sense as the difference in rpms in a 1500 with 3.21's and 3.92's is roughly 400 rpms.

 

[jdefoe0424]

2nd tow today with my 2021 6.4l. Enclosed v nose car trailer with 2 RZR side by sides in it so probably about 7000lbs ish. Towed 170 miles, cruise set at 65mph the whole time. 8.7mpg......meh not great. Pulls fantastic but fuel mileage sucks!

Ouch. What was the terrain like?
Try driving with your foot, I find that with cruise control it's constantly shifting and running lower gear and higher rpm than needed. I'm pretty sure I averaged over 9 with my 6700lb 32' TT. I have a long trip coming up at the end of the week so I will have a much better idea of what the mileage will be after this weekend.

 

[kxnate]

Ouch. What was the terrain like?
Try driving with your foot, I find that with cruise control it's constantly shifting and running lower gear and higher rpm than needed. I'm pretty sure I averaged over 9 with my 6700lb 32' TT. I have a long trip coming up at the end of the week so I will have a much better idea of what the mileage will be after this weekend.

I live in MT, so lots of ups and downs. I actually don't see it shifting a lot with tow haul on and the cruise. Usually only see it shift when you hit a grade like it should.

 

[Firebird]

Mine usually runs 8.5 to 9 mpg pulling my travel trailer, 9000 pounds fully loaded. However, I'm in flat Florida

 

[RAM_Dad]

This is why I ordered the long bed with 50 gallon tank. I know it'll be thirsty when towing, might as well get the jumbo size cup.

 

[Rockcrawlindude]

This is why I ordered the long bed with 50 gallon tank. I know it'll be thirsty when towing, might as well get the jumbo size cup.

I wish mine held more fuel but then I remember that my bladder doesn’t last more than 300 miles in one stretch anyway

 

[RAM_Dad]

Yeah, me either but a lot of gas stations aren't laid out for 50-60ft of truck/trailer. Prefer having extra fuel so I'm not forced to stop, don't have much leeway when getting 8-9 mpg

 

[whitexc]

I wish mine held more fuel but then I remember that my bladder doesn’t last more than 300 miles in one stretch anyway

300 miles....?!!! You are a champ lol. With coffee I have the bladder of an infant. Ridiculous.

Sent from my moto z3 using Tapatalk

 

[Rockcrawlindude]

300 miles....?!!! You are a champ lol. With coffee I have the bladder of an infant. Ridiculous.

Sent from my moto z3 using Tapatalk

 

[Eatonpcat]

View attachment 19372

You look good Brother!!

 

[JohnWedell]

20 ounce coffee in a 12 ounce bladder, what can I say

 

[copcarguy]

Hey all!

I have a ‘21 3500 CCLB 4x4 with 3.73’s. I put the first 500 miles on it empty and then I just towed a small 4,000 lb travel trailer almost 600 miles. The first 500 of that was the “break in” tow @ an agonizing 50mph. I got 14mpg, then on the last 100 miles I got 12mpg doing 60-65 mph.

Doing 50 mph and being 10K + under the tow rating I noticed in tow/haul the truck would basically not go above 6th gear, and ECO would never come on. Turning off tow/haul would get me 7th gear and ECO on downhills. In very hilly or city traffic I’d leave it in tow/haul for the better engine braking.

On the 60-65 mph leg of the trip I left it in tow/haul and the truck would stay in 7th most of the time with an occasional 8th gear on downhills. ECO was a rare sight.

Does anyone know at what weight tow/haul is “required”? Is it a mandatory feature to use with a trailer on the small side?