I have an '02 4Runner that I did a manual hub swap on.

4WD works great with the hubs locked when I want to use it. However I accidently engaged 4WD without the hubs locked and put it in gear. When I did the transmission or ? made a grinding sound. I put it back in park and the sound ended. There doesn't appear to be any damage. But I'm just concerned about what I experienced and if there is someway to prohibit it without the hubs being locked.

 

Your front end relys on being constantly connected via the axles. Once you disconnect the axles, nothing makes them spin. Ergo, if the driveline is spinning and the front axles are not, it will grind. If you lock your hubs, the grinding noise will go away.

Its the same concept for vehicles with factory manual hubs. You can't put the vehicle in 4WD unless A. The hubs are locked, or B. The vehicle is stopped. Since yours orginally was set up for ADD, and is AWD, you MIGHT have to lock the hubs BEFORE you try and put it in 4WD, or its going to grind.

 

That is kinda what I thought. I think it has to do with the ADD, auto trans and center diff being open at that time.

Thanks