I have a new 2008 ranger (4k miles) with 3.0 V6. When driving at around 1500 rpm with A/C on it has a rough or grinding feel to it. Without the A/C it's fine.
Dealer changed the serpintine belt which did nothing to fix it.
My question: has anyone heard of this before. I suspected a faulty compressor but before I battle with the dealer I want to be sure it is not something normal due to gear shift ratio with A/C on.
Any ideas?

 

Do battle.

Make them show you that another truck does that.
They won't be able to. Battle over.

 

I have heard about this issue before. It had something to do with a dirty Mass air sensor or something like that. I have an '04 5 speed and have had the issue when I have my A/C on. Most of the time, I just roll the windows down, so I dont worry about it too much.

 

Almost sounds like a bearing is going bad if it has a nasty grinding feel to it.

 

It could be that or it could be this: Camshaft and valvetrain problem. Did you buy it new or used? Mine does that but I have a wear and tear issue. Mine just turned over 65K miles too.