6.4 Road Trip

So we just did a little road trip through eastern AZ, up to Durango,CO, and back. I stayed off the interstates as much as possible, so the vast majority of this was on two-lanes, and most of it was hilly terrain at 5-8K feet elevation. The truck did OK, but I have to say I was a bit disappointed at how much downshifting was required with an empty truck, just my wife and I and a couple duffle bags of clothes. I couldn't help thinking, man this would suck with a trailer behind us. One annoyance was how often the shift switches on the stalk were unresponsive for the first click, sometimes two. I did find that on cruise the truck would lug a bit then drop from sixth to fourth and scream along, but if I anticipated the hill and dropped it to fifth manually at the foot of the hill, it would give it a chance to make the shift and lock the converter, and would pull many of the hills in fifth, no problem. This transmission is definitely a disappointment overall, both in gearing and programming. Note truck has 4.10 gears.

Trip Stats:
Miles:1197
Avg Speed: 58.31
High MPG: 16.9 Hand Calc
Low MPG: 14.8 Hand Calc
Avg MPG: 15.54 Hand Calc
EVIC Trip Avg: 17.5 (Two MPG off as usual)

It's a big truck with a gas motor...
A set of 456 gears or 488"s would sweeten the pot though. I feel ur pain-

15 mpg for 400 hp 7000 lb truck..
Pretty good if you look at what was available just 10 to 15 yrs ago.

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Ratket said:

It's a big truck with a gas motor...
A set of 456 gears or 488"s would sweeten the pot though. I feel ur pain-

Click to expand...

I can't kick too much on the MPG. I guess that given the advertised HP/TQ for the 6.4 I was expecting a bit more grunt. I do believe a properly built/geared 8 speed would make a world of difference. My last truck was an '05 CTD, and I don't suspect it would have done much better MPG-wise, but on most of those hills it would have stayed locked up in OD and surfed the boost gauge. Again, not beefing. I knew what I was getting into going back to a gasser.

On Edit: Before my CTD I had an '04 Chevy 8.1/Ally and it would not get this kind of MPG downhill with a tailwind, not to mention it was complete pos.

Durango is a nice little town. Did you get to ride the old steam train through the mountains?

It is also about 6,500 feet above elevation. With the normal 3% per 1,000 ft power loss for most N/A engines, the 410 hp at sea level 6.4L is actually around 330 hp in Durango.

SouthTexan said:

Durango is a nice little town. Did you get to ride the old steam train through the mountains?

It is also about 6,500 feet above elevation. With the normal 3% per 1,000 ft power loss for most N/A engines, the 410 hp at sea level 6.4L is actually around 330 hp in Durango.

Click to expand...

Durango was nice, but, like Sedona, AZ, it was a mob scene and traffic everywhere. Long story, but no we didn't get to take the train to Silverton, and that was my original plan. Best laid plans, and all that jazz...

Well aware of the elevation robbing HP.

That 8.1 engine you had waaaaay back in 2004 actually had MORE torque than these new 6.4's do.....Yea, I know....on a good day the 8.1 would get 8 mpg...But then again that motor with the Allison would have NEVER been doing the downshifts like you described on your RAM....Just Sayin........

Ya go go new gears lol

on the trip up the mountains, did you drive in tow/haul mode? When I get out into the Texas hill country, I always use tow/haul. Actually, even for city driving I like t/h. It gets the rpms up around 2k where the motor and tans seem to like to be. Not ideal, but I can average about 14.5 mpg hwy around 65-70mph. City, I'm lucky to see 12.5 mpg. Usually around 10.5 - 11.5.

I hear you about the trans. The motor is plenty strong, but it seems the trans gearing and shift logic suck. If I every have an extra $1k, I might spring for the diablo and unlocked ecu for the trans tuning.

With 37's and 3.73 gears I just keep it in 5th gear and 68-72mph, never have to downshift where I'm at.

The shift mapping on these trucks leave a lot to be desired, what you experienced with the shifting is pretty much par for the course with mine as well.