Determining source of vibration - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 7 (permalink) Old Oct 17th, 03, 07:23 AM Thread Starter
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I have this '86 3/4 ton chevy 2wd truck. After I replaced 2 very shot tires (broken belts), and got some other issues worked out, I now have a bad vibration starting around 45-50mph, and by 65mph it is usually so bad that the truck feels like it is "skating" on the road. But, sometimes it is worse than others. I have rotated the tires, no help, and tried dropping the truck in neutral at speed and that didn't get rid of the vibration either. It is coming from either the driveline, or the rear end. Short of unhooking the driveshaft and having someone tow me down the highway, is there any way to narrow this down one way or the other?

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post #2 of 7 (permalink) Old Oct 17th, 03, 08:57 AM
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Travis,
You may want to try to have someone drive it down the road and you follow in another vehicle, take a look to see if you have a bent wheel, axle, or broken shock. all of these things will cause what you are feeling. if you don't see anything then pull the drive shaft and have it checked for straightness and balance. You might want to climb under the truck and have a look at the u-joints before you get in to deep. Does the steering wheel shake? If not I would bet it is something behind the tranny (drive shaft, rear shock/s, axle, wheel). Good luck, let us know what you find.

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post #3 of 7 (permalink) Old Oct 17th, 03, 12:58 PM
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Have them sign a release form before hand though.

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post #4 of 7 (permalink) Old Oct 17th, 03, 06:12 PM Thread Starter
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Actually, after I replaced the 2 trashed tires (still had a ton of meat left on them too), it vibrated really bad...one wheel was bent. I replaced it, and the vibration moved up to where it is now. I have had all 4 tires balanced twice after cleaning all the dirt dobber nests and dried mud out from the backside of the wheels. I know it is something behind the tranny because I can even shut the engine off at 65 after putting it in neutral and it doesn't change any. I put the rear end up on jackstands and run it up to 55 mph and it was still shaking pretty good. I would think that would take the shocks out of the picture, wouldn't it? All the u-joints and the carrier bearing are nice and tight, but the u-joints was all replaced a few years ago by the previous owner...maybe he got something out of phase? I know a bent axle is a possability but find that hard to believe. Even with all the work I have done on the worn out 305 it still doesn't make enough power to bend much of anything.

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post #5 of 7 (permalink) Old Oct 19th, 03, 01:09 PM
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Travis,
How did the wheel get bent? It doesn't have to have power to bend an axle, if someone smacked a cyrb real good that would do it. Since it did still shake on jack stands (that is pretty dangerous, just in case you didn't know), that would take the shocks out of the picture. That pretty much leaves the axle/s, if you have a dial indicator made you can check the for run out. You may also want to make sure the wheels are the right ones for the truck and that the center hole in the rim is a snug fit on the hub of the axle. If the hole is too big it will allow you to put the wheel on and tighten it up, but it won't be perfectly centered (I doubt that is your problem). If I were in your shoes the axles would be were I would look seriously.

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post #6 of 7 (permalink) Old Oct 20th, 03, 09:27 AM Thread Starter
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Royce, no danger here. I took it out in the pasture and supported it up in the air, so if it did take off, it would have just ran out across an open field before I could shut it down. The wheel was bent when I got it...never put 2 and 2 together to think that whatever bent the wheel could have bent an axle [img]graemlins/clonk.gif[/img] The replacement salvage yard wheel fits snugly like it should. It also has full floating axles so it shouldn't be a big deal to pull them and check it out. Thanks!

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post #7 of 7 (permalink) Old Oct 21st, 03, 01:07 AM
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Since its a full floater axle, i.e., remove axle w/out removing wheel and inspection cover, you might want to check/adjust the bearing preload of the axle (brake drum). Loosen the locknut, tighten nut to remove all slack, then back-off 1/2 to 3/4 flat, then lock down the nut. Runout of axle flange should be less than .005 inch.

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