When should I adjust the valves on my truck. It seems like they rattle a bit under a load or when it's cold. I've got about 170k on the clock now.

 

If they have never been adjusted, check them out. As long as you get them set right and tightened correctly, they don't need it very often. I have done mine twice in the 7 years that I've owned it.

 

I seem to remember reading somewhere every 25,000 miles.

 

I thought is was every 100k??

 

I do mine once a year just 'cause.

 

you're both right.. (well, close)..
the 12V engine is every 24,000 miles...
the 24v engine is every 150,000 miles (135k on severe duty)

here's the procedure for a 12v, similar on 24v:

http://dodgeram.org/tech/dsl/valve_adj/12_valve.html

there are other methods- do a search for valve adjust or valve lash.. it's not difficult, when you get used to it, it's real quick... most of the time mine doesn't need adjusting, I check it, and they're dead on...

 

On a side not , some guys will set their valves at .008 and .018 , instead of .010 and .020, opens the valve a little farther, but still has lots of piston clearance.