Gliding in The Beast - I'm thinking its not worth it under 45mph.

[Jay2TheRescue]

Well, I tried neutral gliding on neighborhood streets on my way home last night, and this morning on my way to work. I'm beginning to think its not worth it at neighborhood speeds. This is what I noticed:

It glides nice and easy, and I guess because it weighs over 3 tons & gets a lot of momentum going, & at low speed wind resistance is not a large factor... It glides quite far. In a couple of places I was able to shift into N and glide up and down a few hills for a total distance of almost 1/2 a mile, and stay within +/- 5 mph of the speed limit. That's the good part.

Here's the bad part...

In most of the streets the speed limit is 35 mph. Traveling at 35 my tach reads about 1400 - 1500 rpm. Stopped, in N it idles at about 725 rpm. Logic would dictate that shifting into N would cut my rpm's roughly in half, making for considerable savings, right? Not exactly. At the same point if all I do is take my foot off the accelerator and let it coast in gear the tach reads 1000 - 1100 rpm. Shifting into N at that point only drops the rpm's to 900 - 1000. A savings at best of only 100 rpm, and at that point IMHO not worth the wear & tear on a 10 y/o 150,000 mile tranny to shift - even though the dealer looked at it this spring for the 150,000 mile checkup & scheduled maintenance and said they could not find anything wrong with the truck.

Then I really got to thinking. I was coming up on a red light, and I was traveling at 35 mph, 1350 rpm. I shifted into N and coasted to the light, watching my tach. Immediately upon shifting into N the RPM dropped to 950. The RPM slowly dropped as my speed decreased, and then quickly fell to 750 rpm when I hit 5 mph. I'm thinking obviously the computer is increasing the minimum idle speed for higher road speeds, and probably does not know and/or care that the vehicle is not in gear. Probably to keep the vehicle from loosing too much speed if you just take your foot off the accelerator. Its got to be an enhanced driveability thing, or is it just a truck thing? If the truck was fully loaded at 70 mph, and I took my foot off the accelerator, maybe it would start engine braking, and that's why the idle increases? To prevent the tranny from getting jerked around too much?

Anyway I'm thinking that under 45 mph I'm just going to take my foot off the pedal and coast in gear (just like I have been doing for years).

I welcome anyone else's comments/thoughts/suggestions on my findings, and would be curious if a passenger vehicle of the same vintage (1998) would behave in a similar fashion.

-Jay