No Torque converter lock up..no codes

[Like a rock 1019]

97 GMC z71
Out of the blue one day torque converter didn't lock up. Put a scanner on it there is no codes and its commanding lock up and there is no problems shifting what's so ever. I noticed there is a slight whine in park and neutral with kind of a clicking noise. Also clunks from same area going into reverse. Curious on what the problem is? Any help would be greatly appreciated

 

[TylerZ281500]

fluid level....first place to start always.

 

[great white]

http://www.sonnax.com/articles/184-No-Lockup-for-No-Reason-

Interesting read...

 

[Like a rock 1019]

Fluid is full smells good and is cherry red. No miss fires either. It did get a shift error 3-4 -40 but it isn't a hard code so not sure what that means