If you are coming from Walnut Creek, you may find Carson pass, though a little longer, actually a faster drive.  The easiest way is to continue on 88, after Stockton, until you get near Gardenerville, NV, then cut across to 395 via Centerville Lane.  You can also turn right at the Markleeville junction and follow CA 89 to 395, near Topaz Lake.  That involves a pretty steep climb up and over Monitor pass and a thrilling 9% average gradient east of the summit.  

The question is relevant because we're planning to cross the Sierra next week to camp at June Lake. The normal way would be thru Yosemite over Tioga Pass but right now you need a permit for that and they sold out on day one. If we can't cross Sonora either it's long way around.

        Rolling Stones "Let it Bleed" 1968.

Dang I was gonna have my r-pod airlifted to the top of Mt Evans and tow it down behind a little Smart Car. 

Engine braking? We dont need no stinkin' engine braking!

I pretty much have been able to go anywhere I've wanted to towing the rpod. If its a rough-ish forest service road I just crawl along at 1-2 mph. If its steep I descend in first using hill descent. There's no rush.  It helps to do those runs early in the morning so you're not feeling like you're holding folks up. 

The problem with many automatic transmissions is that even though they may have 5 - 6 speeds, the shift lever has 3 positions and when descending in even the lowest position, the transmission keeps shifting into the highest gear for that position.  So when you want to stay in 1st or 3rd, it keeps going to the next highest gear and tanking your engine braking dreams.  That's one of the things I like about the newer automatic transmissions, they give you a "manual" mode where you can select the gear and keep it there.

Even today, when coming down "New" Priest Grade, we approach the intersection at the bottom with great caution. More often than not, we find someone at the bottom with smoking brakes.

Sorry, that's not gonna work on a highway or paved road where you are already in motion down a steep grade.

You have to stop completely to switch to 4-LO range, and you are limited to probably 20 to 30 mph or so.

Plus it will be in 4WD which is not to be used on dry pavement.

LO range can sometimes be used to control your descent speed on a steep downhill gravel or loose dirt road (or other slippery surface like wet grass, wet leaves on a hardpack muddy road, etc) to around 2-10 mph on a gravel or otherwise slippery surface, where 4WD can be used, but remember to back off on the trailer brake gain. 

Of course, if you have pushbutton hill descent control, that would be the time to use it!

When I moved for a time to eastern Kansas from Denver I found that some of the hills that I would cycle up were steeper than any that I encountered in Colorado.  Shorter, yes, but steep as &%#$.  Same was true in upstate NY (where I grew up), now that I think about it.

I've driven that descent with our Pod and Dakota and it was not a problem.  I followed the truck speed limits and had no issues with keeping my speed under control.  In comparing my new TV and trailer to the old rig, there is really no significant difference in traveling down steep grades, at least based upon my experience.  It just requires patience and common sense. 

Maximum Grades on Colorado Mountain Passes

Also, for those of you that have careened down the west side of Floyd Hill on I-70, that's a 6% grade and about the steepest that I can recall encountering on an interstate.  Some of the grades approaching the Eisenhower Tunnel are also in that range.  I'd be interested in knowing if there are any steeper grades on any interstate.

Turns out there are.

Found this thread:

I wasn't thinking about interstates. There are lots of rural highways with pretty steep grades and 60-ish mph speeds. A lot of those are pretty straight and then have turns toward the bottoms when you get into the river valleys.  Those are the ones I'm most wary of. Easy to get lulled into bad decisions.  When you see those nice orange signs that say trucks use lower gear do that before entering the descent. 

I think its the long 10%-ish grades on the higher speed roads which are really more dangerous. On a slow winding road the descent speeds are low so you are dissipating less heat in your brakes.  Plus its obvious you will need to be in a lower gear anyway in the twisties so there will be engine braking. Oh the high speed roads you're more likely to feel comfortable and rely on your brakes and not shift down, and you're dropping elevation fast because of your speed, the energy from which goes straight to heating up your brakes. A 10% grade at 60 mph is the equivalent of a 20$ grade at 30 in terms of energy release. 

Either one you have to downshift. I just use sport mode my highlander when in the mountains so I get to pick my gear myself rather than let the computer do it. 

Been down that road (in a jeep, no trailer). Don't recall it seeming that steep at the time but that was a long time ago. The weather in the video is typical East Hawaii, gets a couple of hundred inches of rain there a year, even more uphill at around the 3-4000 ft elevation.  

Nowhere to go trailer camping in Hawaii really. Not many rPods there I don't think 

Unlike freight haulers, we have the good fortune to never really need to be in a hurry.  If we are rushed, we should avoid narrow, steep roads and take a different route.

In most cases, that is passive engine braking, where the automatic transmission will force a downshift if the engine rpm limiting speed will allow it, and otherwise, things are just allowed to kinda do what they do, with no additional hardware to actively retard engine RPM, other than the active downshifting.

We need to get rid of 80hp to maintain 60 mph. And we need to do that for about 10 minutes. 1 hp = about 2500 btu/hr so we will create 2500*80*10/60= about 30,000 btu. That BTU is going into about 100 lbs of steel in the form of brake discs and drums in the rig. The specific heat of steel is 0.12 btu/(lb-F) so the brakes will heat up by about 2500 degrees F. 

Of course, they wouldn't really heat up that much because (1) the hotter the brakes  get the more heat they will dissipate to the air and (2) they will quit doing anything to slow down the rig way before they get to 2500 degrees. 

Interestingly, the melting point of steel is also about 2500 degrees. So you can relax and not worry about literally melting your brakes as you go careening to your death. 

Moral of the story is ya gotta have engine braking on long downhill grades...

5000 feet down lets say, 10 miles? Which if my math is right that is close to a 10% grade...well you better have made sure that you have a guardian angel that can fly fast!

Us physics nerds don't let petty rules stand in our way of learning obscure stuff no normal person would care about..

Next up is to estimate how hot friction brakes would get on a 5000 ft descent at 60 mph towing an rpod with no engine braking. Anyone want to take a guess? 

Be sure not to activate those jake brakes around the kitty cats, might scare 'em into having seizures.,,,

I've apparently planted a seed about engine braking...you guys are learning things that mere mortals (non-CDL holders) have generally not been allowed to learn about.

Or they dont care. Either way.

Next up on the r-pod learning channel: engine braking laws, (not engines breaking laws!) 

And the 'No Jake Braking' signs we see everywhere and how they are totally illegal and un-enforceable, yet they are enforced, and how does that happen? If you know about the 'noise-off' people without googling that, you get credit for an entire chapter!

Also later on in the curriculum we might get into how websites, even ones put together by smart people, get so many 'facts' about trucks and trucking...WRONG. Very wrong. 

But, its summer break and I have things to do...here at the station, me and the pooch have adopted a stray, mistreated, and injured kitten we are hoping to bring back to full health.

Life is complicated, and then just when you think you have it figured out, a wounded stray animal shows up on your porch with no where to go.

Onward and upward....building up 'karma' points to make up for a few I lost in my younger days.

What speed requires the most engine or friction braking to maintain? Looks like right around 70 mph for our rpod scenario. Braking requirement is about the same at 45 and 90 for example. So I guess its bad to take the grade at 70 if you don't have enough engine braking capacity. 

So say you ran out of engine braking and you're at 70 and still accelerating, but you haven't cooked off your friction brakes yet. You have a choice, either speed up to 90 or slow down to 45. As Dirty Harry would ask, are you feeling lucky? 

You can think of gas engine braking as the engine acting as a vacuum pump trying to suck air past the closed throttle, so the pressure differential is between vacuum on the intake side and atmospheric pressure on the exhaust side, which is about 15 psi at sea level. 

On a diesel with no jake or exhaust braking system there is no significant pressure differential between the intake and exhaust sides so no engine braking. Add a jacobs system and now its pumping against the compressed air in the cylinders up to the top of the compression stroke, which is then released by the exhaust valves opening. So the pressure diff can be what the cylinders and heads can stand.

On a diesel with exhaust braking a butterfly valve is typically added downstream of the turbo, kind like a throttle valve in reverse.  so now the engine is pumping against the pressure the valve is creating in the exhaust system. So the pressure diff can be what the exhaust system can stand.

Check out this video to see how all 3 systems work:

Notice that the gasoline engine brake system can only produce around 15psi pressure differential, while the diesel ones can produce more. In fact, either jake or exhaust brake systems can absorb power close to or higher than the hp rating of the engine itself. Why not even more? Because the engine internal components aren't designed for that. You'd break your crankshaft or con rods.

I couldn't find a reference but I would assume that the engine braking available in a normally aspirated gas engine could also be fairly close to its power rating. But in a gas turbo its going to be significantly less than that.

And podwerks you're right, there isn't any reason you couldn't add a jake or exhaust brake system to a a gasoline turbo and get more engine braking. No reason except cost and weight that is.....

The good news for us rpodders is that we really don't need that much engine braking in most situations because of the big parachute we're dragging around. Say you have a typical 8000 lb rig and you're driving down a highway with a 10% grade at 60 mph. You'll need to dissipate power at a rate of roughly 120hp. You'll already be losing about 40 hp from air drag and rolling resistance so the engine has to consume another 80 hp. Even the 2.7 liter engine ought to be able to do that I think. Now if you were hauling 9000 lbs of steel (the tow rating of the 2020 f150 2.7 ecoboost) on a low profile utility trailer you'd need to disspate more like 120-140 hp at 60mph. I'd be taking that hill at more like 30 mph in as low a gear as possible I think.