4 Wheel Drive won't engage
 

My 2000 4Runner SR5 worked great and the 4 wheel drive worked fine. I had 265 75 16 on and i had to drive on a road trip so I put on my regular street all season tires to save gas mileage. I had Big O Tires do the mount and balance and nothing was wrong that I could know but I didn't have to use the 4 Wheel in Arizona but when I got back to Montana I pulled the lever into 4 wheel and the light never came on and it never locked in there wasn't any noises or anything just no 4 wheel. Any help would be great thanks.

Steve

So I just got my 4Runner to engage it's 4wheel but it seems to like to do it more so when I put the transmission in reverse. Would simply changing all my fluids help this problem? I feel like the problem is in the auto locking hubs. Any advice would be greatly appreciated

Thanks
Steve