off idle vibration and my paranoia

[neo]

:o Hi all, I am very new to the list. Been reading and searching for a couple months now, but can't seem to locate any precise thread for this concern/question so I figured it is time to belly-up and start one...
I have an 89 3/4 t 4wd burb I bought initially to use the drivetrain in a conversion for my grand wagoneer. However, once I got it running and started driving it, I have foudn how much I enjoy it. The body looks like crap but it is awesome. My wife hates it but what does she know? I ordered the 6.2 book from the site a couple months back and have read it several times. Dr. Lee and others discuss the vibration damper and the ensuing perils of it going south. I have been noticing a slight grumbling/vibration just off idle. I a have looked at the harmonic ballance/damper and it seems to look fine, but it is nearly 20 years old (I assume anyways). First, is this off-idle vibration normal, second could it be indicative of a dying/dead damper, and finally, is there someone/somewhere (like Penisular) that I can get a very good damper and put my broken crank fears to rest? I want to insure that does nto happen as I really have foudn this to be a great truc and wish to protect/preserve its trusty 6.2 as long as possible. Thanks in advance for the help/guidance/assistance and cajoling.
Jeff

[rustyk]

Welcome to TDP. Just get the damper; at 20 years, it's shot (Mine was no good after 12). It may not hurt the crankshaft, but it's doing the belt-driven accessories no good. It ain't cheap (~$290).

[DA BIG ONE]

Dampers can and do rotate on their hubs, eye em and they look ok, don't delay replacement if it's a keeper.......

[Subzilla]

I've gotten my big parts like dampeners from Team Chevy in Scottsbluff, NE. 800-658-4017. They'll give a much lower than retail price. You really have to eyeball the rubber closely to see some the undesirable cracks. But like the others stated, go ahead and replace it at that age.

[Robyn]

The 6.2 is notorious for grumbling vibrations in the front. The water pump bearings can get loose and this will contribute. The belts also vibrate at the off idle rpm too.
The ballancer is definately a good thing to check.
A late model crank pulley with the rubber isolator will eliminate most of that issue.
The 6.5's all had the serp drive system with the isolator to get rid of all the anoying noise and vibration.
My 91 burb has the isolated lower pulley and its quiet.

Check all the goodies up front for bearing failures and se what you come up with.

Robyn

[neo]

Wow! Great information all. Thank you all very much! I am going to replace it asap. I called around today and recieved prices from 156 from NAPA to 104 from AutoZone. AutoZOne claims to have it available tomorrow and claim it is OEM part made by a company called Pioneer. This price seems pretty low with regards to some of the info, so I am a bit skeptical. I did look at mine tonight and it looks fine, but as stated in the replies, looks don't always tell the whole story. I will replace it anyways.
Come to find out, this engine was replaced fairly soon after the truck (PO I spoke with) was new as the original 6.2 drew the crankcase oil up past the oil rings and ran out of control and killed itself. At least that is what the PO said. It does have the GM Goodwrench 6.2L stickers on the valve covers.
Thanks again!
Neo