wont shift into 3rd gear

i have a 1999 silverado 4x4 5.3 liter motor, truck has 151,650 miles on it took truck to work this morning shifted fine went to go to lunch and no 3rd gear , not had a chance to put on a scan tool yet but will tomorrow, could the 2-3 selniod ? causing the problem? fluid don't seem brunt or any oder to it truck always shifted fine before, so i'll put on scan tool tomorrow and let everyone know what i get.:banghead:

Welcome to AF
You need to get it on a engine/capable scanner and get code no and post back code no before we can help.

Does it stay in 2nd or does it feel like it shifted to Neutral instead of 3rd?

//2000CAYukon

it wants to shift into 3rd but just goes into no gear an if i let off gas it seems like it goes into gear but still not 3rd or 4th tack runs around 3,800 at 45 rpm's

i put truck on scanner tool an no codes of any kind in the truck says no codes found