Keeping RPM's down on downgrade

That can DD15 can handle 2000 rpms just fine. Also, if you ever want to know if the road is icy, look at the other vehicles or even your trailer tandems. If you see road spray, you're good. If not...well...

 

Also, if you ever want to know if the road is icy, roll down your window and check the back of your mirror, if ice is forming on your mirrors chances are high that the moisture on the road is starting to freeze also.

 

The outer edges of your windshield or the forward facing side of the mirrors will tell you if it is cold enough to start icing! You will learn in time, when you need to be light on the throttle....just a bunch of little clues that come from experience and paying attention. Keep in mind, what the road surface is comprised of (asphalt or concrete) will have a drastic effect on surface conditions....give it time and as I said...pay attention!

It's good that you are at least asking these questions!

 

What he said^^^^^^^

 

On your 1st question: If the road was bad enough where it was that icy, you shouldn't be out there in the 1st place...and chances are the road is closed. On the 2nd question: Hypothetically yes. If the rain is cold enough and the ground is frozen, then it could freeze on contact on a less traveled road. But you are getting into what-if scenarios now. Most states do a #### good job making sure their roads are clear. The responses you are getting are assuming that the road is clear and you enter some bad weather.

 

Yep, as long as you don't exceed the governed rpm excessively, you can let it wind at 1800-2000 and get the maximum braking power.

That being said, the Volvo engine brake does a pretty good job at 1500-1600 rpm if you descend at a reasonable speed. I've gone down Cabbage with 43k in the box at 25 mph with the VEB in Auto running 1600 rpm and didn't need to use the service brakes at all to maintain speed.

 

i went down cabbage sunday night. I don't know why the speeds are so slow considering cabbage is a baby hill and everyone goes down at about 40.

i can see ice, snow, and fog. but not when the road is dry and the stars shine bright.

Donners is longer with standard 55 speed restrictions. Parleys is longer with max speed of 45. Vail in some spots limit to 35. Cajon is 45. Grapevine is 35. To name a few on the west coast.

 

The exceeding 1600 rpm is for cruising on flat roads. Most engine makers recommend gearing a truck so that it doesn't exceed a certain RPM because at that point the engine is running beyond its efficiency band.

If memory serve, Detroit recommends gearing for a cruising speed of 1500 rpm at 65 mph for most OTR applications. Using Schneider as an example: Schneider specs direct top gear transmissions with 2.64 rear ends. With LP22.5 tires, that gives you about 1475 rpm at 65 mph. But I believe you can spin a DD15 up to 1700 before you are considered to be grossly inefficient, so that Schneider truck could in theory cruise at 75 mph.