D4 simply locks out the top 2 gears, which are the "overdrive" gears. 'L' limits the transmission to first and second gear only. However, if a shift from 'D' to 'L' would rev the engine above redline in 2nd gear, then the transmission will shift to 3rd gear until the vehicle slows enough to where it can safely shift to 2nd gear, then it will do that. Revving the engine up to redline in 'L' will just hit the rev limiter, with the transmission remaining in 2nd gear.

 

Naive follow-up to your very clear answer: Can you provide a few examples when to use the D4 and L options? Thanks!

 

Glad I searched the forum because I was about to ask the same question. It is really ridiculous that a 600 page owners manual offers no details on this other than each are used when going uphill or going downhill (as the OP pointed out).
So the way I understand it, low is like the old transmissions with shifters that had P,R,N,D,2,1, and shifting into low is like shifting into 2. I used 2 a lot going down Mt. Lemmon in Tucson in my 2003 Ram, and people who didn't use low ended up with brakes on fire . It is something like 26 miles of windy mountain road with a decent from 9300 ft to 2500 ft elevation.
D4 on the other hand, I'm trying to imagine when I would want to use it? Gears 5 and 6 wouldn't be used anyway unless your speed warranted it.

Edit, now that I think about it, engine braking on big hills at higher speeds, (thinking of the decent from the Eisenhower tunnel to Silverthorne on I-70 in Colorado) would probably be a good use for it. You want to maintain 50 -60 mph without using too much brake, and L would be too low for those speeds.

 

If this basic info isn't in the owners manual, how do people know the answers? Is there another source of information (besides this forum)?

 

I live in the mountains and had similar questions when I got my RL. It was frustrating to not be able to simply shift to the gear I wanted. This is what I came up with via common sense and practical experience. I hope it helps.

I use L (both ways/up and down) on the steep winding road from my house to town where it would be crazy to go much faster than 35 mph anyway. (A change of about 1500 feet in elevation over about 3 miles.) A lot of braking is still necessary on the steepest parts. I really miss being able to use 1st in those places.

I use D4 on the long, less winding downgrades on the roads where higher speeds are appropriate. Honestly, I don't notice it makes that much difference other than it might take a little longer before I need to use the brakes to avoid going too far beyond the speed limit. Perhaps it is more useful if you are towing a trailer.

I don't know if this is the by-the-book way to use those gears, but it is what works for me and I've gotten used to it. FWIW, I wouldn't want the new 9-speed. Paddle shifters suck on winding mountain roads; they are never in a convenient spot when you are turning the steering wheel.

 

Paddle shifters suck on winding mountain roads; they are never in a convenient spot when you are turning the steering wheel.

They are in the 9 and 3 o'clock positions which is where your hands should be.

https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/steeringtechniques.pdf

 

Fully crossed up and grabbing another gear is how I live my life.

 

Played around with D4 a little bit on the freeway, as I didn't feel a very satisfying surge in acceleration when hitting the gas to change lanes. Even when flooring it, there is hesitation. Hitting D4 before making the move might be a better way to get that quick surge.

 

Unlike the 9-speed and 10-speed automatics that Honda is using, the 6-speed doesn't mention the ability to skip gears when downshifting. If you're cruising along at 65 MPH and floor the accelerator pedal, it takes longer to shift from 6th to 3rd than it does from 4th to 3rd because of more gear changes and the rotational inertia of the crankshaft, flywheel, and torque converter. Selecting D4 when anticipating a pass or preselecting a more suitable passing gear with the 2020's paddle shifters will result in quicker passing power response.

 

Don't know much about tow / haul. I do know that the ECON button has NO impact on cylinder deactivation. Basically you can't defeat the VCM system by going out of ECON mode. You also don't enable the VCM by going into ECON. VCM is always working deciding if and when to deactivate cylinders.

 

I don't claim to the last word on this but that is not how it was explained to me by the tech's at the dealership. If that were the case how does the Econ mode work? My understanding it that it works in concert with the VCM function. If you shut out the VCM function as many here advocate what impact does it have, if any on the Econ mode?

Home school me here boss... I'm ready to learn.

 

Your dealer' techs are either missinformed or are deliberately missinforming you. You can't shut down VCM without installing an aftermarket device like the VCM Muzzler. It tricks the computer into thinking that the vehicle's coolant isn't up to a sufficiently high enough temperature to allow engagement of cylinder deactivation. . . .Take a look at the VCM muzzler threads and you will quickly realize that no one would bother with buying / installing such a device if it was simply a matter of turing Econ mode on and off.

 

@Capt Steve ECON affects your throttle mapping/response to encourage better driving, uses your evaporator less, and that's it. Snow mode also has a similar throttle effect to help you maintain traction in icy conditions, but it also changes power distribution in the AWD system, so it's best to only use it when needed. ECON however is a personal choice that can help fuel economy if you abide by it's dampened response.

VCM operates independently of the ECON button. On previous car years and models, there was a button called ECO that DID affect VCM operation.

 

@zroger73 how does the Honda software work in the 6-speeds when a heavy payload is detected by the vehicle or if you are towing? I assumed the truck did something automatically, but curious what it actually does.

 

According to Kerry McClure, the Large Project Leader and Chief Engineer for the 2G Ridgeline, the 6-speed transmission automatically enters a "tow/haul mode" when a load is detected eliminating the need for a manual mode. Unfortunately, that interview appears to have been removed from YouTube so I can't link to the source.