General lift question

[Ranbo]

I just installed a Mopar 2” lift on my 2021 Gladiator Sport S Eco diesel. I noticed driving home from work this morning that the transmission mission was shifting down into 7th on the tall highway interchanges. Cruise control was on and at 70mph. I’m running 33” tires for now. I expected with a lift to loose some mileage but not the dropping into 7th. The lift has been on about 48 hours now. is this normal with lifts?

Update: This appears to only happen with the adaptive cruise control. I’ll watch this closer driving home tonight as most of my commute to work is in sub 30mph range.

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[Gren71]

I just installed a Mopar 2” lift on my 2021 Gladiator Sport S Eco diesel. I noticed driving home from work this morning that the transmission mission was shifting down into 7th on the tall highway interchanges. Cruise control was on and at 70mph. I’m running 33” tires for now. I expected with a lift to loose some mileage but not the dropping into 7th. The lift has been on about 48 hours now. is this normal with lifts?

Lifting changes the aerodynamics of the truck and will increase wind resistance. Try dropping back to 60-65mpg and you may remain in 8th longer. There is a well documented, on the forum, correlation with 60mph+ and increasing wind resistance/decreasing mpg.

maintaining the factory rake / plastic bumper / plastic air dam / addition of a tonneau MAY help you a bit too.

anything you do will change the jts ride. So it’s important to really think through your upgrades and how they relate to your build goals

 

[Renegade]

I just installed a Mopar 2” lift on my 2021 Gladiator Sport S Eco diesel. I noticed driving home from work this morning that the transmission mission was shifting down into 7th on the tall highway interchanges. Cruise control was on and at 70mph. I’m running 33” tires for now. I expected with a lift to loose some mileage but not the dropping into 7th. The lift has been on about 48 hours now. is this normal with lifts?

Both 7th and 8th are overdrive gears. Turn off the gear indicator and don't worry about it unless you need a certain mpg to be happy. If that's the case you bought the wrong vehicle. As long as it performs well...

 

[Ranbo]

Lifting changes the aerodynamics of the truck and will increase wind resistance. Try dropping back to 60-65mpg and you may remain in 8th longer. There is a well documented, on the forum, correlation with 60mph+ and increasing wind resistance/decreasing mpg.

maintaining the factory rake / plastic bumper / plastic air dam / addition of a tonneau MAY help you a bit too.

anything you do will change the jts ride. So it’s important to really think through your upgrades and how they relate to your build goals

The front skid plate is off due needing to realign the (pita) fog lights. Thanks.

 

[kevman65]

You're catching air in the front fenders/flares also. You created a gap between the fog light close out panels and the leading edge of the front fender.
Yes those ugly plastic pieces actually serve a purpose.

 

[Gren71]

The front skid plate is off due needing to realign the (pita) fog lights. Thanks.

If you kept your factory rake you shouldn’t need to reposition the lights at all. Did something happen to yours?

 

[glassjawkid32]

Lifting changes the aerodynamics of the truck and will increase wind resistance. Try dropping back to 60-65mpg and you may remain in 8th longer. There is a well documented, on the forum, correlation with 60mph+ and increasing wind resistance/decreasing mpg.

maintaining the factory rake / plastic bumper / plastic air dam / addition of a tonneau MAY help you a bit too.

anything you do will change the jts ride. So it’s important to really think through your upgrades and how they relate to your build goals

Can confirm tonneau will only bring your mpg down.

 

[Gren71]

Can confirm tonneau will only bring your mpg down.

Anecdotally or legitimately?

Anecdotally it improved mine..

 

[dcmdon]

Aerodynamic drag goes up as a square function.

So if you go twice as fast, the drag is 4 times as much.

More practically speaking it means that if you go from 65mph to 75 mph

75/65 = 1.15, 1.15 squared = 1.32.

So you will use about 30% more fuel going 75 mph vs 65 mph.

 

[Imbuere]

Aerodynamic drag goes up as a square function.

So if you go twice as fast, the drag is 4 times as much.

More practically speaking it means that if you go from 65mph to 75 mph

75/65 = 1.15, 1.15 squared = 1.32.

So you will use about 30% more fuel going 75 mph vs 65 mph.

Fuel economy is not entirely a function of drag. Your math is correct from a drag perspective but ignores all the other factors. So, the overall change will be less than 30%.

 

[Garemlin]

Can confirm tonneau will only bring your mpg down.

What's the logic there? You are reducing drag at the rear. I gained about 2mpg when I added a tonneau.

 

[Ranbo]

If you kept your factory rake you shouldn’t need to reposition the lights at all. Did something happen to yours?

I upgraded from factory halogen to Oracle led driving lights in a Motobilt bumper.

 

[Ranbo]

Can confirm tonneau will only bring your mpg down.

It has the factory roll up tonneau cover. I’ve never checked the mileage with it rolled up.

 

[glassjawkid32]

What's the logic there? You are reducing drag at the rear. I gained about 2mpg when I added a tonneau.

Mine lost an mpg, with a hard tonneau anyways. Myth busters did a test on it years ago and found it to be worse as well. I guess there could be a lot of factors though and different circumstances.

 

[glassjawkid32]

What's the logic there? You are reducing drag at the rear. I gained about 2mpg when I added a tonneau.

My logic is that mine may have lost efficiency due to weight. I havnt added a lift or bigger tires yet just the cover.

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