I was driving my 90 loyale to work this morning like normal. When I got into the heavy slush I switched into 4x4 like I do almost daily as I work at a ski resort. Today I experienced a vibration that would only occur when in 4 wheel drive, Also there was a loss of power while this was happening. I switched back and forth and no vibrating in 2wd but vibrating in 4wd and slight power loss. I tried it after work on a the icy but clear roads and same thing. Anyone have a simaler issue? Where should I start looking? Again 2wd was fine-no vibrating and full power.

Manual or Automatic transmission?

are all your wheels the same size?

You should be able to tell if it's driveshaft or axle by the frequency. Driveshafts turn at wheel speed and driveshafts are going at about four times the revs. If you are not sure how fast the wheel goes around slap a big piece of sticky tape on the tread and you will hear it as it goes around.

take a little time to crawl under the back and find out if someone switched the diff if they have then the power loss and vibration you are experiencing is the car trying to tear it's self apart. and if you haven't had the power loss before it may be because you were on a slick enough surface that one pair of wheels could slip.

 

 

my .02

Possibly a U-joint in the center driveline.

I is a manual transmission, same size stock wheels with new snow tires. Everything on the car is original. I have owned it since it had 68,000 miles and now it has 132,000 miles. One day it was fine and the next- vibration. It was not as sever today and I was able to stay in 4x4 and keep an RPM of 3,500 that seemed to smooth things out. I will crawl under it on my day off.

I once had a problem just like this on a 82 wagon. I went under it and found a cord of nylon rope had wound up and around the input into the rear diff. So darn tight that I had to cut it off with a knife. I dont know how long it had been there. When I shifted into 4wd the car almost came to a stop.

Mike