Driving in AUTO... Why do I vibrate on the highway?

[Freyspath]

So I have been meaning to ask this for quite some time.

When I got my Pathy, I noticed the 4wd system had 2wd, auto, 4hi, and 4lo. Very cool stuff! Much better than my 4wd and Low range options on my explorer.

Auto I noticed just drives the car in "All wheel drive", 2wd does just that, and 4wd hi/lo are true 4wd.

My question is though, if you drive the car in AUTO why does it starts to vibrate after you go faster than 50mph? I tried it the other day on the freeway, and when I switched to 2wd the vibrations stopped.

Why is that?

Does it hurt the car to drive it in AUTO all the time? (granted I do drive the car 90% of the time in 2wd)

[WINNIPEGS_MOST_WANTED]

Had mine to 75 mph on the icey highways last week in auto. No vibration here.

...and yes; it was probably a bit fast for the conditions

[QX4ME]

My understanding is it is OK to drive in AWD all the time, which is the same as 2WD if there is no slippage.

I use AWD only when road is wet.

[t_b0ne3]

Just drove mine this past week in auto and it's no different than 2wd? I'm thinking you may have a bad cv joint up front? Could be something else maybe fueler could help out with this??

[Freyspath]

Well I usually only drive it in AUTO when the roads are wet, but when I wanna go on the highway and its.... raining, or wet, the moment I pass 50mph the car gets all these vibration buildups

[naladude911]

No point using AUTO only for snow imo. I use 2WD even in snow, and until I start slipping do I put the car in AUTO. I only use 4HI/LO if I am driving in deep snow or I get stuck. AUTO eats up MPG as well.

[bmlawless]

I have no vibrations when driving at freeway speeds in AUTO. I've seen claims that AUTO is identical to 2WD until it starts slipping, but I truly believe there is a difference. My MPG goes from 14.6 to 13.1 when I drive in AUTO. A couple of weekends ago we were on a road trip and when coasting, I could feel the difference in drag when I switched AUTO on/off.

[Pat Connelly]

Check the U-joints on the front driveshaft.