Vibration after putting into 4WD
 

Hello,
I have 1995 Blazer with 90,000 miles. I have driven it all summer, runs like a top. It snowed last week for the first time so I used 4WD. I noticed a shutter at about 50mph and higher. Shakes the console, the dash and steering wheel.
Not sure why this was happening, so I put it back into 2WD, but now the shutter remains. I am sure it's in 2WD because only the back tires spin.
The shutter seems speed dependent (More speed, more shutter), and also happens after shifting into neutral. There is also no difference in the shutter upon acceleration or deceleration.

Thanks in advance for any insight.

Bad u-joint in the front driveshaft perhaps?

The shutter started at the exact moment I put it into 4wd. I was setting still when I pushed the 4wd button

Well, get your descriptions straight...:icon_wink: You could have a combination of problems. Check your front driveshaft.

How would you check the front drive shaft? Im having the same problem and i was thinking that maybe the front u-joint was going bad. my truck shutters like crazy at 50mph in 4wd hi and i was think maybe its having trouble enguadging 4hi all the way or something.

Just an update for anyone searching that finds this, my problem that was pretty much the exact same as the OP was not actually caused by the u-joint but actually instead it was another vacuum leak from a hose I forgot to connect while I was on the side of the highway working on my truck in the dark after I replaced the fuel regulator. I am beginning to think 80% of any problem people have with these trucks/engines is caused by vaccum leaks. So if you truck shakes going over 50mph and the light says its in 4wd but you have 0 traction look for vacuum leaks.