Transmission Clicking

My manual shift Tacoma TRD with 70K miles has started clicking whenever I change speeds. The clicking sound sounds like slop in a gear train, but this is unlikely. I read some other messages concerning axle wrap but am not convinced this is the sole problem. Some people suggested that greasing the slip zerk fitting on the transmission shaft is the answer.

Well, I have dedicated tomorrow to find out the cause of this annoying problem and supply a solution. Check back soon!