I Have a 97' F150 4.6L with the 4R70W tranny. Going down the road today it made a clunk sound then two more Clunks before I got it pulled over. I was doing 60mph. Looking under it everything seemed fine. I got back in and pulled it in to drive. It started making a whining noise sort of like when it is in 4wheel drive at high speeds.It showed it was still in 2 wheel drive though. I got it home and started taking tranny and torque converter out to check things out. Turns out the front differential had locked the wheels in 4x4 even when the shifter was in 2wd!! Can anyone help me figure out what on earth happened and what I might need to replace to fix this???

 

OK, I got it figured out. It was the Transfer case. The clanking was something inside of it breaking, causing the chain to slide over into 4wheel low and now it is stuck there till I get the transfer case replaced. When going down the road I can reach down and shift the 4wheel drive from 2H to 4H to neutral to 4L with absolutely no change in the driving whatsoever. Hope this helps anyone else with this problem in the future.