kartracer13

I'm getting a vibration from about 2000rpm and up. I've checked everything I can think of and everything is tight. I'm thinking it's the harmonic balancer. It's an LS1 with 104,000 miles. Any ideas?

rod442

manual or auto? coould replace it for preventative maintenance at this point. Do the stock ones slip like the fords when the rubber gets bad in em? Do they even have rubber in em?

how about pushrods, rockers, or weak valvesprings? Throwing out idea's.

Rule out the drivetrain? If its a stick, maybe in the clutch? does it do it with the pedal in and out when in neutral?

same with an auto, does it do it in N or park?

or is it just at speed, in gear?

kartracer13

I'll check when I go to the bank later today. It's an auto and it just got rebuilt again because the torq. converter died after only 4,000 miles. I had a slight vib. before but it seems worse then it did,but that maybe just me. I'll post later after I go to the bank to see what I find.

kartracer13

Yes,it vibrates in P and N,but it's a deeper sounding vib. The motor mounts are new poly and are tight,so I think it's the harmonic balancer,but I really don't want to spind the money just to find out that that's not it. Oh well,it's only money,right.

rod442

looks like on ebay a new oem one is 80-100, or a low end aftermarket is around a hundred bucks too. Plus a new stock bolt, 10$; or a 30-35$ arp that can be reused. Not the most expensive route to eliminate that as a possibility.

HOWEVER, I would think that if it is bad; you would be able to SEE a wobble in it when its running.

quote from another board:

As long as the elastomer(rubber) is good and not cracked or pushed out between the outer and inner part of the Harmonic Dampner then its good no need to replace it. Also if the inner/outer hubs are lined up and not offset.

Changed the plugs lately? its an auto, so pushrods are less likely; but maybe pull the rockers and check them and the PR's anyway? or maybe the stock springs are getting weak? kinda doubt thats it, but who knows.

kartracer13

Thanks for all the info. I guess I have some hunting to do. I do most of my own work and just not looking forword to digging in so deep. I'd put it in the shop,but I hate paying $60+ an hr. for something I can do myself. I'll get poking around and see what I can find. Thanks for giving me some ideas were to look.

kartracer13

I looked at the H.B. and I'm sure that's atleast most of the problem. Next queston is how well would a 25% underdrive H.B. work for an street car? Or even a 10% underdrive? Or should I just stick with the stock size? Talk to me,I'm not sure were to go from here. I am going to get rid of the A/C. I live in Oregon and would only use it 2 days a year anyway.

WhiteHawk

Are the motor mounts aftermarket? Some of the aftermarket poly parts can transfer a ton of vibration into the cabin. I always go with factory stuff if I can.

-Geoff

kartracer13

Ya,they are good polys but the vibration is getting worse and I can see a chunk of rubber that's gone out of the HB. So I know that's the problem,atleast most of it. Now I'm just trying to fig. out what brand and what % underdrive to go with. It's mosty street and some autocross. Any help with that would be nice. I'm looking hard at the 25% underdrive,so I just need to find the brand that will work good for money. I'm not trying to brake the bank.

WhiteHawk

The GM ones are around $100 new. Like I said, I stick to stock stuff wherever I can. The testing GM has done on their parts is awe-inspiring.

-Geoff

MachinistOne

The Powerbond/Pioneer units are less than $300 and are SFI approved - you can get it in 10% underdrive. I use them quite often and they're excellent units for the price.

Most important thing for you to do is to use an installation tool to pull the new damper on, never use the bolt to do this as countless people break the bolt off in the crank snout.

rod442

and remember that the bolt is non reuseable, so get a new one.