So, quite inconveniently, my 4wd has decided to just come undone. It will go into 4wd, but quick acceleration (or high speeds (5mph+) or some other random variable) will cause the 4wd shifter to come loose (seems like it vibrates loose). There is a weird sound, like a loose belt or something, and nothing works (no drive, no reverse, nothing but putting it into neutral, coming to a stop, turning off, and starting up again without 4wd).

I've found that I have to hold the 4wd shifter in place while driving to keep it in 4wd, but sometimes it vibrates so hard it comes out anyway and injures my hand in the process. Has anyone else heard of this? My mechanic had no idea what it could be, suggested the tire treads were different (I had problems with it just not engaging at all when the tires were different sizes until I replaced them with tires all the same size). The tires are the same size, but with slightly different tread. I really don't think it's the tires. He also suggested that I go to a transmission place, but I don't know about that either!

Any ideas? Help! My car won't move in the snow without 4wd and I need it this winter or I will be trapped!

 

I should add that this was in my 98 rodeo

 

sounds like a transmission problem.
dont know too much about 4wd, but does the shifter for the 4wd have its own box and setup separate from the transmission? if it does, you can try to find a new one for it. if not, you will need a new transmission. best of luck!