Was towing my boat down the hwy last night for the first time. total weight is probably right around 5900lbs with a full tank of gas.

My CC with a Hemi and 3.92's was pulling on the way to the lake with the wind about 75mph and running about 2300 RPM.

On the way home going straight into a 15+ MPH wind was doing about 70mph and the truck was down shifted and running 3000 RPM.

Just wondering if this is all good or if the truck should have up shifted itself.

BTW I was in Tow/Haul mode.

What are your experiences?

 

Sounds normal

 

Just an FYI

Based on your experience, I'm convinced that 4:10 ratio is the way to go with these rigs for towing over 3,000lbs.

My experience on the 05 Dakota with 4.10's shows only a slight reduction (5%) in highway NON-TOWING MPG compared to the original 3.92's

...but a huge improvement when towing over 3,000lbs. The Dak with a 4.7 seldom shifts out of 5th and rarely downshifts to third.

 

so just out of curiosity, how far would you drive with the truck pulling in third gear like that?

 

As long as the temps remain normal (coolant, engine oil, tranny oil) but I don't like the following while remaining in 3rd gear:

Poor MPG
Noise when Mechanical fan clutch engages to prevent overtemp
Increased wear on engine at 3,000rpm

I haven't towed my RV with the Ram yet and since it has a 32gal tank, those long stretches on I-10 in west TX with no gas stops won't pose the problem that the Dak with a 20gal tank did, so the economy issue becomes somewhat moot I suppose.

Maybe I'm asking too much for a "dinky" little 5.7 liter with 390HP to tow a 4,200 lb trailer consistently under 2500rpm...

but I don't think so.

 

im with you here man, i was a bit surprised.
i could literally watch my gas gauge drain.

obviously the wind was the issue, but ****, it's always windy in NE!

 

Here is the effective gear ratio for a truck with 17' tires.

So in third gear, a 3.21 axle has a better effective ratio (3.21) than 3.92 in 4th (2.94). I expect a lot of controversy here but I am just having fun with numbers.

The problem in towing with the Ram is the distance between the transmission ratios. So dropping from 4th to 3rd with the 3.92 means RPMs.

With a 4.10 in 4th the effective gear ratio is 3.08 so you may be able to do 70 in winds at lower RPM.

Attachment 8360

 

you can't get 4.10's on a 1500 model, i don't think so at least

it's 3.92's with LSD.... are you using the ERS on the shifter? elec range select?

 

You are totally discounting the amount of wind drag that your trailer has. If you have a head wind, it's going to totally kill your mileage and put some heavy load on at 70mph.

Not to mention that the Hemi's produce better power when revved up.

Tow/Haul mode also changes the truck's shifting logic, making it downshift a little early so you aren't down on power.

I can't believe you guys are worrying so much about a little RPM. Yeah, it's a bit more wear, but I honestly doubt you can tell unless you run the engine until it dies from compression loss - and then it might cost you a few thousand miles of engine life before the rebuild - big deal.

To be honest some times you are better off doing a little more RPM with less throttle input than less RPM with more throttle input.

All the above said, the gear ratios on this truck suck - it needs a 6 speed (or, though unprecedented on a truck, a 7 speed). This is my only complaint at all about the truck. Give it a good 6/7 speed with some good ratios, and we wouldn't need all this BS about different diff ratios.

 

That is exactly what we are bitching about.

In a TRUCK, a 5.7 oughta put out better than a 4.7 in the 2200rpm and below range.

IT DOES NOT. IT PUTS OUT LESS.

The low end torque and HP are sacrificed for drivers that want to boast about going 140mph or clocking a 13 second 1/4 mile.