1986 Chevy Truck deceleration

Tiny
OUTHERE
  • MEMBER
  • 1986 CHEVROLET TRUCK
  • V8
  • 2WD
  • AUTOMATIC
  • 70,000 MILES
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?
Thursday, December 11th, 2008 AT 12:54 AM

8 Replies

Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
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.
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Thursday, December 11th, 2008 AT 2:39 AM
Tiny
OUTHERE
  • MEMBER
  • 6 POSTS
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
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Friday, December 12th, 2008 AT 9:56 AM
Tiny
OUTHERE
  • MEMBER
  • 6 POSTS
I feel it in the drivers seat
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Friday, December 12th, 2008 AT 10:18 AM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
Is your rear transmission mount sperated or broken?
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Friday, December 12th, 2008 AT 4:09 PM
Tiny
OUTHERE
  • MEMBER
  • 6 POSTS
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.
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Saturday, December 13th, 2008 AT 12:20 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
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.
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Saturday, December 13th, 2008 AT 1:21 PM
Tiny
OUTHERE
  • MEMBER
  • 6 POSTS
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.
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Wednesday, December 17th, 2008 AT 12:47 AM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
' Ya done good. Glad you got it. Have a nice Christmas.
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Wednesday, December 17th, 2008 AT 8:30 AM

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