86 Chev 4.3l - Vibration at speed

I noticed someone on here with idle issues on their 4.3l chevy engine so I'm
posting my problem...

86 Chevy G10 van, 4.3l V6, automatic overdrive transmission.

When driving, moreso at higher speed, there is a "resonance" vibration and
it's driving me nuts. It seems to be more related to engine speed than
vehicle speed and seems to be worse when under load, making dropping into
Neutral difficult to gauge changes in the vibration.

- Driveshaft was balanced about two years ago and it made a great
improvement to the ride.
- Hanger bearing is less than a year old (two piece driveshaft)
- Rear wheelbearings replaced. Rearend seems OK.
- New shocks all around
- New tires/rims installed
- New wires, plugs, rotor, cap, fuel filter, air filter, PCV valve,
Thermostat.
- New fan clutch
- Oil/filter changed
- Timing is set correctly
- Carb cleaned and adjusted
- Visual inspection of U-joints and front end seems OK... but I'm just an
amature.

I've had the van for about 10 years, and it sat for a few years before I got
it, making me suspect the engine.

Any ideas where/how to go from here?

A rusted out muffler can make that kind of noise/resonance in some
cases. Also, if the exhaust system touches any part of the car body,
even just barely, it can also create that kind of vibration/resonance.
Same problem if someone put hard mounts on the exhaust system instead
of nice soft rubber hangers. I've had both happen on different cars.

On Sat, 28 Oct 2006 18:36:50 GMT, "Noozer" > wrote:

>I noticed someone on here with idle issues on their 4.3l chevy engine so I'm
>posting my problem...
>
>86 Chevy G10 van, 4.3l V6, automatic overdrive transmission.
>
>When driving, moreso at higher speed, there is a "resonance" vibration and
>it's driving me nuts. It seems to be more related to engine speed than
>vehicle speed and seems to be worse when under load, making dropping into
>Neutral difficult to gauge changes in the vibration.
>
>- Driveshaft was balanced about two years ago and it made a great
>improvement to the ride.
>- Hanger bearing is less than a year old (two piece driveshaft)
>- Rear wheelbearings replaced. Rearend seems OK.
>- New shocks all around
>- New tires/rims installed
>- New wires, plugs, rotor, cap, fuel filter, air filter, PCV valve,
>Thermostat.
>- New fan clutch
>- Oil/filter changed
>- Timing is set correctly
>- Carb cleaned and adjusted
>- Visual inspection of U-joints and front end seems OK... but I'm just an
>amature.
>
>I've had the van for about 10 years, and it sat for a few years before I got
>it, making me suspect the engine.
>
>Any ideas where/how to go from here?
>