Harmonic balancer, injectors, timing chain?

At idle my engine has a slight vibration that seems to smooth for a second then a brief and slight vibratation/shudder, this keep alternating. this just keeps doing the same thing constantly at idle then smooths out once above idle. Also the engine seems to rattle a little louder than some other 6.5's that I have inspected. Mine idles steady at 600 rpm.

The vibration kind of reminds me of when you have a slightly bent rim on a car and it vibrates in a pulsing kind of rythm but will smooth out at higher rpm's(just had to replace one for this reason on wifes minivan).

I have been reading posts about balancer and seems like the likely culprit but has been doing this since I bought 40K ago. I have looked at the balancer and the front side isn't showing any bulges, but I can't see behind it.

I went ahead and purchased a new one off ebay for $50 with shipping and I will go ahead and install it but I was hoping maybe others might have some input.

Also if anyone interested, on eBay someone is selling new vacuum pumps for $79. http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=42605&item=7963531306&rd=1

ChevyDave,

Mine does the same thing. On a gasser I would say it had a vacuum leak or bad spark plug wire kinda thing and doesn't do it at anything but idle. I have been told by the dealer and a reputable diesel shop here that it's injector time. I am at 102K miles.

Don't forget the pulley up there too. My pulley had slipped and caused a rattled and rough idle.

NVMTNLION-Your right it feels like a bad plug wire in a gasser, or a corroded terminal in the cap.

BOWTIE- I'll check the pulley when I pull it off.

I won't pull it apart until at least next week after the balancer arrives.

Easy to see backside of pulley while on truck while laying on your back and looking up at the backside. That way you could order one now instead of waiting longer. Look for busted rubber and if the metal stops are hitting each other.

if you replace the balancer, you might want to replace the pulley as well, they are both culprits.

mine does the same thing, but it doesnt do it all the time it just takes spells