6.4 Hemi Road Trip

[TFucili]

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)

 

[JR]

Does the 6.4 utilize a 68rfe as well?

I've noticed the same delay in the shift buttons on the shifter. I have to press it twice to change a gear. I was thinking that may be by design to prevent accidental shifts.

 

[TFucili]

The 6.4 comes with the 66RFE. What I have read is it is the same gearsets and many components as the 68RFE, which is why it is a really poor match to a gas motor, but in the 545 case. As far as being designed that way, I can't say, but sometimes it does respond on the first click. Things that work inconsistently are extremely annoying to me.

 

[Mark31]

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)

Looks like nothing much has changed since '98. I had a 360 1500 that would downshift at 70 if it smelled a hill on interstate. I think maybe my 88 S15 with a 160 hp 4.3 could pull as much in overdrive as that (laugh) Magnum! On the opposite end of the hp/torque scale from the Dodge, was/is my 1974 C60 Chevy with a 350 rated at 155hp, 1974 type-rating. With its diesel-like power band, it will PULL from 1100 to 3300 rpm.

 

[slowmover]

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)

I'd expect to have to downshift often with a 7000-lb truck and a motor with relatively high TQ and HP peaks.

Pickups hit the aerodynamic wall hard at 60-mph. No way around it. Huge HP penalty.

A great idea to get out there and run it. 58-mph is pretty fast average. Knowing how to make it move well between 55-65 is what matters.

Agreed about shift inconsistency. I'd bring it up to the dealer. How responsive are the brakes is the other part.

Steering is the real truck problem. All else matters not too much.

In the meantime, keep learning what it wants.

I spend my day going up and down through the gears. Being smooth and in control trumps all other approaches.

There are boundaries to respect.

There's a correlation between fuel economy, reliability and longevity Brake and tire life are other indicators.

Where those lines cross on a graph is how to understand planning a trip. And vehicle familiarity is the right path.

 

[TFucili]

I'd expect to have to downshift often with a 7000-lb truck and a motor with relatively high TQ and HP peaks.

Pickups hit the aerodynamic wall hard at 60-mph. No way around it. Huge HP penalty.

A great idea to get out there and run it. 58-mph is pretty fast average. Knowing how to make it move well between 55-65 is what matters.

Agreed about shift inconsistency. I'd bring it up to the dealer. How responsive are the brakes is the other part.

Steering is the real truck problem. All else matters not too much.

In the meantime, keep learning what it wants.

I spend my day going up and down through the gears. Being smooth and in control trumps all other approaches.

There are boundaries to respect.

There's a correlation between fuel economy, reliability and longevity Brake and tire life are other indicators.

Where those lines cross on a graph is how to understand planning a trip. And vehicle familiarity is the right path.

No doubt, speed clobbers MPG, but the posted limits are generally 70-75, even two-lanes are often 65. I generally hang pretty close to the limit, and we only had two delays for road construction. I try to make time by keeping the wheels turning, not so much by going like a house a'fire.