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Old 04-07-2010, 02:50 PM
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Need help with vibration in S-10

Hope someone here can shed some light on a vibration problem. Here's situation:

1992 Chev S-10, 4.3L V6 with TBI, auto trans 4x4, with 175K miles. VIN code Z

I have only owned and driven this truck for about 2 years. It was my brother-in-law's who passed away so bought it from my sister.

At 1750 rpm, there is a noticeable vibration both when truck is in motion as well as stationary. However, vibration is more noticeable when moving. I've read that some 4.3's have some kind of balancer in the motor but haven't gone into block to check things out.

I thought it was due to the center drive shaft bearing (it has a two piece drive shaft) but changed that out this past weekend and vibration is still there. Motor is still strong despite the high miles and would like to delay diving into this motor as my 57 Wagon is calling for me to start work on it

Any suggestions or thoughts to resolve this problem are welcomed. Thanks,

bkt

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Old 04-07-2010, 05:12 PM
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Hi,
First about the carrier bearing, pay attention when you diagnose a problem, you said the vibration was present moving or sitting still, the carrier bearing can't be giving vibrations if it's not moving.
90* v6's are naturally unbalanced just due to the geometry
the balance shaft helps reduce these harmonics. You can have the bottom end balanced.
Rich
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Old 04-07-2010, 09:18 PM
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Richard,

Carrier bearing...so that's what it is called.

So you're saying rebuilding and having the crank balanced is the only way to resolve this? Wow, have to look into that and see if living with a little shake won't cost an arm and a leg.

Thanks,

bkt
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Old 04-07-2010, 10:10 PM
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It may just need new motor and trans mounts, the rubber goes bad and the natural vibration that the V6 has becomes more noticable. You did say it has a lot of miles on it.

Rebalancing the engine won't change anything.

Has the vibration been there for the 2 years you have had it and you are just now wondering about it or has it just recently shown up??
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Old 04-07-2010, 11:16 PM
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Quote:
Originally Posted by 57Handyman
At 1750 rpm, there is a noticeable vibration both when truck is in motion as well as stationary. However, vibration is more noticeable when moving. I've read that some 4.3's have some kind of balancer in the motor but haven't gone into block to check things out.

I thought it was due to the center drive shaft bearing (it has a two piece drive shaft) but changed that out this past weekend and vibration is still there.
1992 was the beginning of the balancer shaft in the 4.3L V6 engine. There were both balancer shaft equipped and non balancer shaft equipped engines used at the same time.

One way to tell the balancer engines from the non balancer engines is to look at the timing cover. The '85 to '94 non-balancer engines use the same cover that was used on the small block Chevy. The balancer equipped engines use a tall metal cover with 10 bolt holes. This was used from '92 through the '95 "first design" balancer motors.

If there's oil on the rubber of the motor or transmission mounts, this will often over time cause the rubber to soften to the point that the mounts will become basically metal on metal. Just old age will deteriorate them as well. My money is on it being nothing more (or less ) than faulty mounts.

Another possibility is loose fasteners- motor mounts, mount through bolts, tranny mount to X-member or to the tranny, loose accessories, etc.

Even longer shot is a balance problem w/the torque converter/flex plate or a loose/cracked flex plate. If there has been any tranny work done, there's a chance the wrong flex plate was used- the 4.3L flex/flywheel uses a unique to the 4.3L V6 balance factor. But in any event, there should be an added on weight attached to the flex plate.

A good inspection will shed some light, no doubt.

Last edited by cobalt327; 04-07-2010 at 11:26 PM.
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Old 04-08-2010, 12:28 AM
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EricNova,

Thanks for your response. I was beginning to wonder about faulty motor and transmission mounts. I will check them out tomorrow.

Cobalt327,

Thanks for the info about how to identify a balancer vs. non-balancer motors. I will look at that tomorrow as well. But, what are my options to resolving the vibration problems if it is not due to a motor or transmission mount problem?

Thanks guys,

Blaine
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Old 04-08-2010, 05:15 AM
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Quote:
Originally Posted by 57Handyman
EricNova,

Thanks for your response. I was beginning to wonder about faulty motor and transmission mounts. I will check them out tomorrow.

Cobalt327,

Thanks for the info about how to identify a balancer vs. non-balancer motors. I will look at that tomorrow as well. But, what are my options to resolving the vibration problems if it is not due to a motor or transmission mount problem?

Thanks guys,

Blaine
The TQ converter will have (in most cases) welded-on balance weights- look for a place where one was, but is no longer. Same thing w/the flex plate.

Don't forget to check the accessories. Even a bad fan clutch unit can cause a pretty good vibration. On your truck, you can temporarily remove the serpentine belt and run the engine just long enough to see if there's a difference in the vibration.

Try disconnecting the AC clutch wire temporarily. It will often cycle on and off even w/the controls on settings other than AC.
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Old 04-08-2010, 11:27 AM
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Your 92 VIN code Z is a TBI engine and it does not have a balance shaft. The W code CPI engines have one.
I have a 92 VIN Z TBI Bravada it has a little vibration most noticeable at idle, I can't say I notice it any other time.
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Old 04-08-2010, 12:34 PM
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While the VIN code might indicate the actual engine that's in a vehicle, IMO it cannot be relied on- there were alot of these 4.3L V6's that were replaced -especially going all the way back to the early 90's.
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Old 04-11-2010, 12:44 AM
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Many thanks for all the advice and excellent information. Have not had time to look at mounts; I'll have to do it next week. The vibrations aren't as noticeable so the carrier bearing replacement may have helped.

Again, thank you for contributing.

Blaine
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Old 04-11-2010, 12:57 PM
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Not sure where your vibration is coming from, but I have a '93 S10 4.3L that shook noticeably while idling. Turned out to be loose hardware at the y-pipe where it meets the exhaust manifolds.
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