Nissan Repair: 01 FRONTIER 5SPD, shaft bearings, input shaft

Question
I have an 01 Frontier that has some transmission issues. I suspect that the gear clusters have gone south..again! the gears were replaced under warranty at 37k and now @ 137k the trans, is making a loud humming noise in 1st, 2nd,3rd,and 5th gears. 4th gear doesn't make a humming noise. It also makes a clicking sound in all gears. Today while driving home from work it started lurching in all gears but especially bad in 5th. It started out with just a knocking noise from the trans when I let it idle in neutral with the clutch let out so, I thought it might just be a throwout bearing initially but the other problems crept up today. I really think that the gears might need replaced. What do you think? The ceramic gears in these trucks seem to be a problem don't they? Thanks.  

Answer
Steve,

To start with it sounds like the input shaft bearings are going out from the knocking you describe.  Now, if you have had all of these gears screw up in the past and they are doing it again. I would opt for a wrecking yard replacement or you are going to spend a chunk of change on replacement of all those gears, bearings and the like.  Use synthetic fluid on the new transmission and see if that does the trick for making it last longer.  I ahve synthetic in most everything I own.