Vibration in 4 wheel drive
 

My 1990 has some vibration in 4 wheel drive high, She is all stock except recalls for heads Toyota recalls and a fer other recalls. A transmission with 111,000 miles put in 3 years ago. 199,089 on the clock now, No vibrations when driving at any speed in 2 wheel drive.She has been well taken care. Everything works except the vibration. It is slight and seems the whole vehicle not just the steering wheel, She is has a automatic.. Any help would be appreciated.

Certain speeds ?
might help to describe a bit more what the symptoms are...
my first inclination would be u joints...

Driving on pavement? I would expect some vibration as you are tearing up the tires.

It is slow on pavement 20 mph or less. I just do it for two miles through a straight neighbor hood going to the grocery store. Once a week or so just to put some miles on 4 wheel high. Hard to describe it is a hum. Like you would get with an exhaust that messes with you at a certain speed and rpm. Michelin M/S dry rot rot before i need to change 31-10-50 R15. CVT boots like new. No leaks. Axles have only the slightest movementt when I shake the hell out of them. I get the part about no 4 wheel drive engaged on dry pavement. I new it was bad turning but slow a straight. I will take your advice.

Will have the U Joints gone over .......

that slow it's probably not u joints but won't hurt to check them...
I'd probably put mine on blocks... put it in 4 wheel high and try to isolate where it's coming from...
trans, differential, transfer case?

I get something similar, just posted din another thread, but my LBJ have excessive play and my drivers side hub needs a repack (possible replace not sure yet). I'm waiting on some parts to do the work but I'll post back if you haven't figured it out yet.

My symptoms: Vibration in 4wd when getting above 30-35 on snow covered roads, increased under acceleration. From what I can tell the u-joints on the front shaft are fine and I don't get it in 2wd.