I have a 1999 Chevy Silverado 1500 service four-wheel-drive light just came on and it is stuck in four Lo it does not want to come out it runs and drives fine but I can't go faster than 30 miles an hour any idea what this could be

 

Yah your vehicle is stuck in 4 wheel drive and can not get out of it. Your trying to run all 4 wheels past 30 mph which is usually the drop out speed. You need to fix the problem of not being able to get out of your four wheel drive. The only other possibility I could see is a bad Vehicle Speed Sensor but doesn't sound like it in your case.

 

It sounds like a bad actuator or switch. I would say to the best of my knowledge that your actuator is bad. Make sure you got truck in neutral when trying to shift out of 4wd.

 

That is sound on. He is absolutely right with that. Sorry I was answering about 50 plus post yesterday over more major transmission and engine work stuff but wanted to just give you the idea where it lyes.

 

There is one thing I failed to mention that most will overlook is that you can also have bad electrical connections locking you into on. I would start with the actuator though and see if it fixes it as it is a cheap piece.