1986 Chevy Truck deceleration

1986 CHEVROLET TRUCK
70,000 MILES • V8 • 2WD • AUTOMATIC
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OUTHERE
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On deceleration within the 55-65mph range my c20 shakes and wobbles. I put new tires had them balanced twice and even took the truck for a second opinion. The wheel bearings were repacked. the wheels balanced on both sides of rims, and also aligned. Still shakes and wobbles. Engine runs smooth when idling and accelerating. Transmission shifts smooth. Couldn't get the universal joints to clunk. Tire pressure ok. The more I work on the truck the less noticeable the shake and wobble is. Is it all in my mind?
Dec 11, 2008 at 12:54 AM
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JAMES W.
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Do you feel the shake mostly in the steering or the driver's seat? Do you have a CV joint in the drive shaft? What type of truck is this, C10, C30, S10 etc Please advise.
Dec 11, 2008 at 2:39 AM
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OUTHERE
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It's a C20 with no CV shafts. It's rear wheel drive.
Long bed. I don't feel it in the steering. The closet
I've come to feeling where it's coming from is the engine to rear end.

Outhere
Dec 12, 2008 at 9:56 AM
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OUTHERE
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I feel it in the drivers seat
Dec 12, 2008 at 10:18 AM
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JAMES W.
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Is your rear transmission mount sperated or broken?
Dec 12, 2008 at 4:09 PM
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OUTHERE
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It wasn't separated or broken. But it was soft. When I Pushed on the driveshaft near the tranismission by hand it moved. I replaced it. So far it's about 66% less shake and wobble.
Dec 13, 2008 at 12:20 PM
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JAMES W.
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Now we're getting to the nitty-gritty. Is your drive shaft bent or out of balance? You can check the driveshaft for bend by lifting the rear wheels and setting a jack stand close to the center of the shaft with a pointer taped to it. A pencil, screwdriver, anything will work, and spin the shaft by hand while watching the clearance. It doesn't take much warp to make a shaft wobble at 3,000 rpm. The balance can only be checked accurately by a rebuild shop. Let me know.
Dec 13, 2008 at 1:21 PM
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OUTHERE
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The driveshaft was out of balance. I had them balnce it. Has a smooth ride now. While the driveshaft was out I had them replace the universal joints at the same time for some trouble free miles.
Dec 17, 2008 at 12:47 AM
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JAMES W.
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' Ya done good. Glad you got it. Have a nice Christmas.
Dec 17, 2008 at 8:30 AM