I have a 1993 w150 and have been experiencing a problem with the four wheel drive on it for about a week. I had to put in four hi to get out of my field and now the light hasn't came off but it is in two wheel. When going down the highway when I get up to about 50 the light goes off and let off the gas then it makes this unbearable screeching noise. If I slow down around 20 or 15 mph it will bounce real hard and the light will come back on. When ever it did this I decided to put the transfer case into four high (probably not the smartest idea on my part) and then back into two wheel and the light came back on and it didn't make that noise. I have auto locking hub and I think they aren't unlocking. So I'm going to go ahead and order some manual ones because I've been wanting to do that for awhile. If anyone has any ideas I'm open to them. I would appreciate it.

 

I agree with converting to manual hubs. I just did mine a few months ago. Great swap. I think the issue you were having is likely your central axle disconnect. (CAD). Its a vacuum operated system that engages your 4wd via a shift fork in the middle of your axle housing. The vacuum system is well known for not working correctly when the rubber hoses get brittle, leak or come disconnected. Check out my post about converting to manual lock out hubs. I explain how to over-ride the CAD so that your axles are constantly locked, allowing the manual hubs to do their jobs. Good luck!