My truck will only shift into reverse gear and has no forward gears or park. The only way I can keep it stationary is by engaging the parking brake because it will start rolling when it's just in park.

I've read through a few threads and it appears that if this was a 2WD, it would indicate something had broken inside of the transmission, likely the forward clutch. However, because this is a 4WD, it may have something to do with the transfer case or the differential. In 2H, I can only get reverse, and cycling through 4H and 4L still only get me the reverse gear. In 2H when I shift to manual 1 from park or neutral, I can hear a clunking sound from behind the cab and there's a slight change in RPMs, but the truck has no go. There are small changes in RPM when I put the shifter into manual 2 or drive, but no forward gears are engaging and I don't hear any sound from the transmission indicating the truck is trying to go into gear. The only time I can get it to move is when it's in reverse, and then I have no problems.

When I drove it about three days ago, the truck was fine. No odd noises and no shifting problems. I had an oil leak from my valve cover gasket so the truck was out of commission for two days while I waited for the new gasket, and I took off the exhaust manifold, EGR and throttle body to access the valve cover. I don't think anything I did for that job could have caused the transmission, transfer case, or differential to have gone bad. That being said, it now doesn't drive at all after I replaced the valve cover gasket.

So far, I checked the fluid level and found that, when slightly warm, the fluid was in the crosshatched area of the dipstick. I then dropped the transmission pan and verified the fluid was still a deep red, and there were no metal shavings in the pan indicating anything had broken in the transmission. I also opened the fill plug on the transfer case and saw that the fluid was up to the fill line and, like the transmission, a nice deep red. Before I dropped the pan, I tested for codes and received 113 (IAT sensor is/was high or open – IAT) in KOER and 111 (System checks OK) in KOEO.

Does anyone have any pointers on where I should look next?

 

Look above the gas pedal first:

(click this text)


Then follow each of the other links on that page, read, and inspect/repair your truck. I hope you put Ford/MC Mercon ATF back in the trans - you're NOT supposed to change it.

 

I tightened up the shift linkage with no effect after you posted. I finally got the transmission out yesterday and took apart the forward drum, the frictions and steels were pretty burned up. So I think that's the culprit. Thanks, Steve.