99 Tahoe Non Auto-Trac

Does anyone know if the Non Auto-Trac (shifter on floor) 4x4 Tahoe's are shift on the fly or are you supposed to stop fully before shifting into 4hi? I've owned this truck for about 4 years and have always come to a complete stop when shifting into 4hi or 4lo. The reason I ask is because a buddy of mine swears up and down that you can shift into 4hi at any speed. I'm pretty reluctant to try this without any further confirmation. Thanks in advance for any input on this subject.

You can shift in to 4hi while moving, as far as how fast, consult your owners manual. I definalty would not try doing it above 30 mph. I know someone that thought that they would see if it would work at 60+ mph and well can you say new t-case and fron diff.

Well problem is that I don't have the owners manual. Thanks for the input.