Weird vibration that comes and goes

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kenh

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1990 C1500 that's been lowered but not sure how much as the PO did it. It has spindles in the front and shackles/brackets in the rear. Frame is not notched.

I have kind of a weird vibration that comes and goes. Thought it was tires and had them balanced (twice) but it's still there. Looking at the driveshaft it looks like it is almost strait with no angle at the rear or front. Haven't actually measured it yet. I know from past experience in an industrial supply house that 3 degrees is considered "ideal". Does that sound correct for this vehicle? I replaced both joints about a year ago as the rear was getting loose. Not many miles since replacement and that never changed the vibration issue.

I plan on new A-arms, tie rods and sway bar bushings but don't think that has anything to do with my vibration issue.

Has anybody experienced an issue like this? I'm sure I forgot some info so please ask.

Thanks!

Ken
 

Drunkcanuk

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I'd get an angle finder and check. I think you answered it already. If it's good, then maybe get the driveshaft balanced. And ya, I've heard the 3 degree number tossed around before.
 

Joe Dirte

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Had a u joint go bad n acted like that. Thinj when id let off the go pedal. If it's at ~60 it's usually a balance issue. Around 20 or lower I think its usually bad tire.
 

kenh

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Comes and goes based on what?
Driving down the road it appears and then goes away more or less randomly.
do you feel it in the steering wheel or in the floor?
In the floor mostly but at times very slightly in the steering wheel. Rotating tires doesn't seem to make a difference or at least very little. That's why I think it has to be drive line related. BUT it's not a high speed vibration like a driveshaft. More like an out of balance tire.
Is the vibration only at certain speeds or RPM? Or always there?
It seems worse at higher speeds but can be felt at speeds above 45ish or so.

I have a digital angle meter so just have to crawl under and check the shaft angles. First I have to find some ambition to do that.....

Ken
 

1998_K1500_Sub

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Has anybody experienced an issue like this? I'm sure I forgot some info so please ask.

If you had a radial force variation in two or more tires, and their sizes differed slightly (could be the same sized tires, just slightly different circumference) they might vibrate noticeably when the radial force variation coincides and then become un-noticeable when not. Even if the tires are exactly the same size, as you drive through curves on the road the phase between the tires will change and the vibration may coincide (noticeable vibration) for a short period of time... and then shortly later, not coincide (no vibration). Uneven wear patterns in the tires might yield the same result.

My 10yr old set of Bridgestones on my Suburban generate their own set of unique noises, e.g., a growling type of sound / vibration during low speed, when braking.

One or more bad cab/body mounts can cause noises, or amplify chassis vibrations, in inexplicable ways... that is until, you finally figure out it's the mounts that are bad. I can't tell you how long I beat my head against *that* problem. See https://www.gmt400.com/threads/help-with-cabin-vibration.59533/post-1265343

Speaking of tires and vibration, I had a trailer that seemed to invoke a vibration in the truck. On straight-aways, the vibration was unpredictable... sometimes it would do it almost continually, later it might not do it at all. I wasn't sure if it was "tires" or some sort of odd "chassis / trailer" dynamic interaction. Then one day I was rounding a long curve in the road, at road speed, and I noticed the vibration came... and went... and came... and went, and I knew then and there it was related to the trailer tires and their relative phase to each other. In that case, I had the trailer tires balanced and the problem went away.

In your case, you've had the truck's tires balanced, but I'm guessing they weren't checked for radial force variation. Even so, some other oddity in the tires might invoke vibrations in the truck at times when the tires are in the proper "phase".

$0.02
:popcorn:

Or it could be something else.

Borrow a set of wheel / tires from a friend's truck, if you can, and try them on yours.
 
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kenh

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1998 I tried to quote your thread but the fracking adds covered the insert quote window....

That was my thoughts also on the tires going in and out of phase. The truck came with a "cheap" set of tires and one of them took 3 1/2 ounces to balance. The vibration can go on for 10 miles or more and disappear for one mile then come back again. Rounding curves doesn't seem to make much difference. I'm wondering if one is slightly out of round????

It's just a goofy thing. My gut tells me it's tire related but I'm going to check that driveshaft angle also.

Thanks everybody for all the input. Oh the joys of owning a 32 year old vehicle! :rolleyes::rolleyes:

Ken
 
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