Which Harmonic Balancer?

[thx1138v2]

I've developed a vibration in the steering wheel of my 1994 GMC C1500 4.3L V6 LB4 that I have determined to be the harmonic balancer. When I start it in the morning and the engine is cold there is no vibration at all. But when I get it up to operating temperature there is a fairly strong vibration.

In trying to locate one (of many) I have narrowed it down to a Summit Racing Dorman 594-817 or a Dayco PB1105.

The Dayco one is the one on the left in the photo and the Dorman is the two photos on the right.

I don't have the old one off yet but I'm guessing it is the Dorman on the right that I need. If you look closely at the photos on the right you'll see that the one with the rectangular box has a raised portion while the one on the left does not.

I have a doctor's appointment tomorrow afternoon. I'm hoping it will hold out that long. It'a about 60 miles round trip. What would happen if the hub comes completely loose from the balancer? Would it still be drivable or should I get a cab?

Any advice would be helpful.

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[Schurkey]

If the damper comes apart, you're looking at a totaled radiator, potentially totaled timing cover.

If the damper inertia ring is that loose, you've maybe already got crankshaft/bearing damage.

I had an inertia ring come off of my 283 damper. Drove it maybe 30 miles. Replaced damper, thought I was OK.

Couple months later, engine blew up--all the crank bearings were toast.

So did the failed damper take out the crank bearings, or did the failing crank bearings destroy the damper? Or were the two things unrelated?

I have no idea...but I've been suspicious of failed dampers ever since; and over the decades I've noticed that failed dampers installed on failed cranks are surprisingly common.

I thought the V-6s were neutral-balanced at the front like the V-8s. But I don't know that for sure. I stay as far away from 90-degree V-6s and Iron Dukes as I can get.

 

[GoToGuy]

How did determine it's the balancer? Have looked to see if it's shifted from original factory position? If it's moved, it's out of balance/ harmonics as soon as it at idle regardless of temp.
The steering wheel is great for vibration analysis as it can replicate a " tuning fork " and determine if the felt vibration is vehicle speed velocity dependant or shifts vibration speed feel with engine rpm.
Have you ruled out any of those conditions for steering wheel vibration?
Wheel balancing out? Any worn steering parts? All u joints in good condition?
Good luck.

 

[thx1138v2]

I determined the problem was the balancer by eliminating everything else. It vibrates whether the truck is moving or sitting still once it heats up. That rules out the steering parts, wheel balancing, ujoints, and suspension parts. I checked all of the mounting points like motor and transmission mounts and body mounts. And the truck has +250k miles on it.

My thinking is that it's fine while it's cold in the morning after sitting overnight but when the crankshaft heats up it heats up the balancer hub which softens the rubber, allowing the whole balancer to wobble and vibrate.

Can anyone think of anything else?

It sounds like I should take a cab to my doctor's appointment.

 

[thx1138v2]

I took a cab to my Dr appointment just to be safe.

After I got back I found that I could get my fingers between the back of the balancer and the front of the timing chain cover to feel around. I found the raised area as shown under the yellow rectangle, so I've ordered the part. I'm not at all sure how long it is going to take to get it. I'll let you know the results after I get the new part on.

 

[b454rat]

What about the trans? Did you unbolt the convertor to eliminate that? I had a trans fail from drilling the holes in the flexplate, werent drilled right and eventually took the trans pump out. It didn't vibrate, but took longer n longer to move as time went on.

 

[thx1138v2]

What about the trans? Did you unbolt the convertor to eliminate that? I had a trans fail from drilling the holes in the flexplate, weren't drilled right and eventually took the trans pump out. It didn't vibrate, but took longer n longer to move as time went on.

No, I did not unbolt the converter. I just checked that the mount was present and tight. I had the trasmission rebuilt back in 2004 or 2005 but I haven't had any problems with it so far. Of course that was 17 years ago so I guess that could be it.

I've got the harmonic balancer ordered. I think I'll put that in and if that isn't it I' ll take it to my transmission guy.

 

[Schurkey]

You need to define "vibration".

How do you know this isn't a misfire "shake"?

 

[Hipster]

Have to agree with Schurkey. Something like an ICM or coil can start to act wonky when it gets warm when it's on it's way out.

 

[Supercharged111]

You need to define "vibration".

How do you know this isn't a misfire "shake"?

This is the first thing that came to my mind.