...to slip into neutral if I'm going downhill or fast enough to coast for a mile or two? How bad or is it for the gears and transmission?

 

Shouldn't be bad for anything. It'll help drop the RPMs down and increase your mileage.

 

Nothing will happen at all.

 

I wouldn't do it, when the you are coasting over a distance like that the pcm will turn off the injectors, but if it is in neutral the injectors are firing to keep the engine running. Food for thought.

 

It's not bad disengaging it, however engaging it can be hard on it. In reality, the trans comes out of lockup when you take your foot off the throttle anyway and also your throttle body is closed and injection is minimal during this time as well. I guess it would save you a little but I don't like doing it.

Now in a standard transmission, hell yea I will do that all the time, but not in a automatic.

 

if its auto just pray you dont shift to R then itll be bad for everything lol

 

as adukart said, shifting into nuetral while coasting downhill will gain you nothing, it wont damage the transmission, but will not gain you any fuel economy (will actually make it worse) for the reason mentioned, the PCM knows that the momentum of the truck is pushing the engine along so the fuel supply to the cylinders is REDUCED not completely shut off, but it is reduced in order to help with fuel economy.

 

Mine shut off, at least that's what I thought. I was pulling a buddy's ford f-150 on a car trailer down the interstate. We started descending on this hill that was a 5% grade nothing huge but my live readout shot all the way to 99 and stayed there. Until we reached the bottom then it when back to 8.

 

The only way you will go into reverse is if you pull the lever toward you. You can freely push the lever into Neutral and it will stop itself, it's a safety design to help cover dodges ***. It is also something that manufacturers have been doing for many years.

 

Yeah but the possibility is there