Help calm my nerves with this issue

I can only assume that it's physics...that the hill must just not be steep enough to maintain the momentum you need to stay at that speed. It is a relatively fast speed. But not knowing the hill myself it's hard to say. I certainly haven't noticed the car slowing down while going downhill, but I haven't been down any that fast.

 

Jack up each wheel and see how well it spins... Also maybe tire alignment... Downhill coasting in neutral should be significantly less resistant to the downhill when the car is in drive or in B mode...

 

While this cars coefficient of drag is low for a hatchback your Previous car could of been lower. Also this car is pretty heavy for its size but your old one may of been heavier.

 

Make sure parking brake is not engaged?

 

Lol. Had a ex that did that lol.

God I hate her

 

maybe post the route, or at least the downhill section, from google maps.

 

It could be hand brake adjustment that is too tight or rear brake shoes adjusted to tight in the drum or defective front caliper that keep too much pressure on the disk or defective bearing. Since you put it in neutral and it did the same, it's not transmission or motor related. One thing for sure, it's not normal ! How is your fuel MPG ? Is your tires under inflated ?

 

Regen braking can cause the car to slow down on very mile hills. You could try coasting (gliding) although neutral would work the same. Are you sure you were in neutral?

 

Mine speeds up going down even small hills as long as I keep a light foot pressure to keep regen off. Either the hill is an optical illusion (don't laugh - it can be that way) or something is wrong with your car.

 

Did you have cruise control set? Mine will attempt to maintain the set cruise control speed when going down hills.

 

Another thought, make sure you are in D not B!

 

Ageless, I agree with others... this is something wrong with your car or what you are doing. My C2 will eventually slow down when I pop into neutral on a flat stretch of road, and it will even slowly speed up a mile or two if there is the slightest downward incline. Slowing down in the situations you described is not normal.

 

An Avalanche is a lot heavier than a C, therefore it has more momentum and reacts differently to hills. In particular, it would accelerate more rapidly while going downhill than the lighter C. On most of the hills I drive, I don't decelerate while in D. If I move to N I'm pretty sure I would accelerate, but not very quickly. If it is a steep hill and you aren't accelerating slightly in N then I would assume something is amiss.

Things to check if you are worried: Tire pressure, brakes (perhaps they rub), oil clarity, fuel type, overall engine tune-up.

 

I do not think a Prius should slow down going downhill in Neutral, but depending on the grade, it could slow down with the transmission in Drive.

If it slows down in Neutral, you should take it into the dealer.

 

It depends on the combination of speed and slope. I don't expect my liftback to maintain 65 mph when rolling in Neutral down a slope of just 1 or 2%, it is going to need something like 3%. There is still a lot of air drag at that speed.