Looking at LE2 for Fulltime - which of my concerns are valid?

[Raspy]

It seems most trucks are geared too high for my liking. In an attempt to get the absolute best mileage, they are running the engines at a high idle on the highway.  And seemingly assuming the truck will be operated with no payload.    This is OK for unloaded conditions, but means, when towing, that the truck has to drop 1 0r 2 gears to begin to pull a hill, or a headwind.  And the mileage is not noticeably better because of it.

 

The new Cummins 6.7 engines, since 2013,  are tuned differently that the older 5.9s and early 6.7s were.  The new ones are tuned to avoid smoke under any conditions, and consequently will not pull well below 1600 RPM.  The older ones were tuned to reach full torque at 1400 RPM.  And with the 3.42 standard gears it means about 1500 RPM is common on the highway.  This means it will downshift to do anything.  At that point, the theory of "higher gears means better mileage" goes out the window.

 

Don't fall for the idea that mileage will always be better if the engine is running slower.  Not so.  A certain amount of HP must be produced to do the job at hand.  If the engine is running below it's volumetric efficiency RPM (not on the cam), it will be running inefficiently and while still able to get the job done, may be getting worse mileage than it would at a slightly higher RPM.  Then there is the issue of how drivable it is.  When it has no throttle response and it has to downshift to work, it becomes very annoying.  It also means that you will lock out the upper gears. This negates the gearing theory and deprives you of more gears to work with.

 

My Cummins, for instance, came with the standard 3.42 gears.  When towing, I had to lock out 6th, and sometimes even 5th, to make it pull well.  I've spent a lot of time in 4th, (direct drive) while towing heavy loads.   Even while towing my Oliver, I liked being in 5th better than 6th.   I changed my gearing to 4.10 and it became a different truck.  More useful gearing, less shifting, better throttle response and the mileage is just as good as ever.   Also, 1st became even more torquey.  It was so worth the change.

 

My Rubicon is the same deal.  I wanted the 4.10 gears instead of the standard Wrangler 3.23 gears.  The Pentastar has to get over 2000 RPM to get into the fat part of the torque band.  This RPM is where it becomes efficient and has useful power.  At 60 MPH, it is turning about 2100 RPM and is nice to drive. At 70 it is in the high torque area of the curve, without getting into the V6 buzz zone.   I'm also getting about 19-20 MPG with it.  With the 3.23 gears, 6th would be a useless gear.   So, the higher gears would mean fewer useful gears and bad mileage if I tried to use 6th.

 

It was the same story with my Dakota.  The gearing was so high that 6th was useless.  So I re-geared the truck and made it much nicer to drive.  The mileage was no worse, and maybe better.

 

I've done this with two other trucks too.  All with similar results.  Your truck needs to run efficiently at the RPM you will be using it at and it needs to be responsive to the throttle, or it becomes annoying as it lugs along, gagging for air.  Simply expecting better mileage, by slowing the engine down, is not gonna happen.   Then, while driving on secondary roads, or around town, you want lower gears, because you have more useful gears, and lower gearing for repeatedly starting out from stops.

 

Modern computer controlled fuel injection, and variable valve timing have made engines run much better than a few years ago,  but they still have to be tuned to pass the EPA emissions tests.  Modern gas engines, with variable valve timing, have a wider efficient RPM range.  This really helps with mileage and drivability.   Diesels must not smoke any more than necessary, in order to not prematurely clog the DPF and cause too many regens.  Cummins is a victim of this requirement, as are all diesels.   What is an inherently torque heavy design, is detuned at low RPM.  They pull like a locomotive at 1800-2200 RPM though.  And the new HO has 1000 ft lbs of torque.  Yikes!  The only tranny that Chrysler has that will hold that much power is the Aisin.  It still has about 20% of headroom, even at that.  The 68 RFE tranny, used with the lower output Cummins, is a good tranny, but in a different category.  Lighter duty.  The Aisin will run at full throttle all day and never overheat.  It's torque converter is strong enough to pull a dump truck around and be fine.

 

Remember, automatic transmissions are called "automatics" not "smoothies".  Being able to feel a shift is desirable.  It means it is not slipping and it is getting the shift over with as soon as possible.  This means less wear and less heat buildup.  There is always a balance with automatics between too smooth, and possible slipping, and too rough for comfort, but no heat buildup.  Lockup strategy is now part of each shift, except maybe in first, or in some special conditions.  It's not a separate function that occurs at some predetermined vehicle speed or throttle position.  The majority of heat in an automatic comes from a slipping torque converter while under power, and that has been eliminated as much as possible.  They also must stay locked during engine braking.

[Landrover]

I am toying with a 2020 Chevy 1500 if I can’t find the dodge/ if the diesel offers 1800+ payload in the LTZ trim, it would be worth the tradeoff of having to watch our weight vs a 2500 or 3500 with 1000-2000 extra pounds of payload. “MrTruck” showed a 2WD with an 1800lb payload so it’s possible (double cab 2WD GVWR 6900 vs 4WD GVWR 7100 or even 7300 on the diesel 4WD CC). There the diesel is the same price as the “truck” gas engine, and has the potential to turn some greater mileage. Downside is losing the sealed bed storage and having to add weight for containers or a topper vs Ramboxes which don’t steal as much payload.

 

I saw TFL Truck’s video on the PW. Their numbers lined up with what I saw on the Laramie. For an HD gas engine it stands alone as the current chevy/ford gassers were giving me ~12-13 MPG vs the 15-17 on the RAM 2500 6.4. 2020 will definitely change that. Speaking of TFL trucks, I wish they would focus a little more on testing the trucks and running their flat loaded/unloaded loops and ike loaded loops (not really as interested in that test – if I drive that roads it’s because I chose to drive that road). Their latest videos have stupid clickbait titles like “do my feet smell after driving 10 hours?” and don’t really provide any valid comparisons or data.

 

To believe we towed a 3-ton tractor through the cascades with an inline 6 F250 with 100hp/190lb-ft torque back in the day puts things in perspective ?

 

Check  YouTube  truck gauntlet challenge they compare all trucks on mountain climbs and down grades towing heavy loads, may help.

[WhatDa]

I think that's the TFL guys.  They just lately have been doing more silly tests than anything.  Their Ike runs are cool, but I also want to see the MPG loop on level ground that they sometimes do.  That is 99% of my towing on the east coast.

 

MPG Loop:

The GMC Sierra 1500: 9.8 mpg

The Ram 1500: 9.2 mpg

The Ford F-150: 8.7 mpg

 

 

But the problem is now 90% of their videos are fluff pieces like this: https://www.tfltruck.com/2019/07/can-a-tuned-650-hp-ford-expedition-grocery-getter-outrun-a-mustang-gt-v8-video/

 

It's cool and all but they haven't even tested the new 8 speed 2500HD outside of the PW.  Maybe they have been waiting for the 2020 Ford and GMC offerings.

 

 

As far as my TV deliberations go, I got emails in the last couple hours of

 

1) RAM 2500 cummins with 2010lb payloads with what I want in terms of other features (others were under 2000 before with extra bloat) - simultaneously another dealer confirmed that the Silverado LTZ 6.2 that is on his lot has 1990 Payload - within 20lbs of the Ram 2500 diesel.

 

and 2) an invitation to place an order on a 2020 Silverado 1500 Diesel.   The math seems to work out that we could fit everything into the Chevy 1500 diesel's payload guestimate (200-300 lbs heavier than 6.2 is my current guess), but then we are back to the Andersen Hitch and watching what we put in the truck along with tongue weight.  ~30MPG highway empty and probably still pretty high towing might make it worth the added fuss.

[WhatDa]

#1) Wife now agrees on composting toilet (yay).  Sales says its too late to change, seeing if service can install it for a reasonable price after we are "complete".

 

#2) Tow vehicle: I think we've paired it down to two options at this point in the 1/2 ton range (and two now more distant challengers in the 3/4 ton arena): 2019 F150 (Pro Trailer Assist) or 2020 Silverado 1500 with the 3.0 Duramax.  Still waiting for more details on the Duramax.

 

 

[Overland]

Sales says its too late to change

That seems silly, considering what's involved (or isn't).

[WhatDa]

Completely concur. But maybe I am in timeout for asking for some of the crazy stuff during the order.

[Landrover]

I was told many times that if any changes are to be made, that they have to be made before production starts.  Any changes after that it would be a add on by the service department. Must be due to the higher volume and quality control.