IIRC, too much backlash will eventually result in broken gears. it wouldn't hurt to open it up and study the setup - some of that blue machinists layout fluid that shows the contact area would be helpful here. also study the u-joints, as they may be on their way.
remember that maintenance costs less than emergency repairs

 

Every year I look everything over, check for slack in the front end and driveline. Always tight, u-Joints are nice and tight, and greased every oil change.


Heh, ain't that the truth!

 

well its good that you keep up on it, but u-joints can wear out without being obvious until they're gone. in my case, the front joint had no slop i could feel, the the rear only had a little bit of slop in a vertical direction (not rotational), but when i replaced them, i found that both joints had significant wear, though not severe. i've heard it said by a number of people that the only way to be sure it to take them apart and look

 

True enough some times. IMO on u-joints, they dont need changed until theyre loose, even if the are dry. Just did my dads, was squeeking to beat hell but was tight. Pulled it, and 3/4 of the needels were broke and it did bind some, but was still truckin. Not to bad though 20 years and 200k miles it lasted, almost to the tee.

 

The original Spicer parts in these trucks sure lasted a long time!