Help won't shift into 3rd

[excursionMark]

Ok so we got 22 inches of snow this weekend so ive been in and out of 4x4 a decent amound because it was impossible to drive without it in certain areas and today I was driving and notices that the truck was sitting at 2000 rpms and I never really get into it so I don't see it there pretty much ever so I let out then get back into it a bit and notice it's not shifting into 3rd gear ... Think I need a new tranny or is there some simpler fix ... I had things to do so I parked it and my buddy is driving me aroundnow and I havent gotten to check any thing like fluids or test it without OD or anything so should I look for anything?

[excursionMark]

The fluids were fine and I tested it with OD off and it shifted through all fears nicely ... Is there any bad side to running it with OD off and how long do u think it will last if I baby it?

[ipz2222]

Trans should shift 1-2-3 the same with od on or off. A one time no shift to any gear does not mean you have a serious problem. If it reoccures, them you have a problem.