Before I did mine at 55K, I was hearing 1 valve tapping. If it makes a fairly distinctive tapping sound at idle, you might want to check the valves. I know the manual says 120K for adjustment, but I prefer to do it more often.
Valves usually loosen up with time, but if they start tightening up, you can't hear it and you won't know if you've stretched a valve stem until it's too late.

I don't think you'll see your mileage suffer, but you should notice the extra noise, and the extra looseness can cause a hammering effect on the valve train and wear parts prematurely.

 

also if the tapping goes away as the engine warms up then you do have a loose valve. . .however if the tapping continues on a 3rd gen then you have an injector issue

 

Kinda hard to distinguish tapping from all the other engine noise. These things ain't no Lexus. But I'll check it soon. Thanks.

 

Yea, on a 96, it would be more difficult to hear. With the mileage on yours, it is probably time for an adjustment

 

yea. . .a 12 valve you just have to do. . .theres no listening out for it.

 

just wanna confirm...i get a i guess "clanky" sound when shes cold and once she warms up its fine. its kinda loud though.? valve adjustment is what im thinking? anyone agree?

 

Just for quick reference to the Vavle Adjustment for the 24V trucks (2nd Gen's)...
http://mopar.mopar1973man.com/2002%2...adjustment.htm

 

I just adjusted mine at 157K miles for the first time and this thread helped me tremendously!!

Thanks Dave for taking the time to do this write up.

 

I did my adjustment yesterday, but need to pass on some info that might save someones engine, seriously.

I've got a 2002 1-ton Dually with the HO CUmmins, 6-spd, with 99770 miles. I'm also a dragracer and had my ASE certs and an ATA in Automotive Technology so I familiar with engines,mechincs. I had to preface my statments with the info so I don't get accused of being a tard.....

So, to the point. I really loved the pics and all the other stuff that was posted. The process isn't new to me, but I needed toque specs and valve sequence to be adjusted. And it's the ORDER that turned out to be different on mine. Mine only had 5 valve cover screws and there was no tubes into it. Just the valve cover. I followed the order presented here and it was fine until I got to EXHAUST #3. Not only was there not a gap to be adjusted (at position #1) but the valve was open! I finished the rest and went to position #2 and found the same problem with EXHAUST #4, BUT EXHAUST #3 was loose and able to be adjusted. The point being - 3 & 4 are backwards, at least on mine, a 24V version. Where this would be dangerous is I went ahead and played devil's adcovate and adjusted to the letter the order. Well, when #3 gets to position 2 the gap is about 3/8-1/2"!!!! So someone that a virgin DIY probably may not catch the problem..... Aother thing that was different was their was no 'normal' timing mark on the crank dampner. The only mark I found waws a small square with a line through it on the FACE of the dampner. Furthermore, the engine was at TDC with this mark pointed DOWN at 6 o'clock, NOT up at 12....

Now, only one valve was actually in spec, but the rest weren't really out that bad. The #1 intake was actually tight. After I got everything back together (the reusable gasket is awesome!) Now it should be noted that I've noticed for a while now that on initial startup there'd be smoke out of the tailpipe, but not after I adjusted the valves. It's seemed quieter, smoother, and the test drive seemed like it had more power for less throttle. We'll see for sure when I tow one of our race cars again next weekend down along Mt. Hood...

Hope this os helpful to someone. I know what ws here already was a help to me.

Thank you!

 

Super Dave -- Super job on 24 valve adjustment. Thanks you