Weird Vibration

[85Silverado]

Maybe you guys can help me on where to look. I have this vibration that is rather disconcerning...at low speeds it's not really noticiable...but at higher speeds (like coasting on the freeway) it's quite noticiable...it's like


vibration silence vibration silence vibration
\/ \/ \/ \/ \/
rrrrrRRRRRrrrrr.........rrrrrRRRRRRRrrrrrr......rrrrRRRRRrrrrr (with like a 1 to 2 sec gap between the vibrations and the vibration lasts maybe 2 seconds)

It comes in softly gets louder and silences off again and then like a second later it starts again.

Anybody got any ideas? Thanks again.

[85Silverado]

I don't think it's u-joints....there's no loud clunk when shifting between drive and reverse....and I hope it's not pinion bearings...sounds like it'd be hard to fix..hehe...and that's not something i want to fix in 20 and lower degree weather..hehe

[swervin ervin]

You definetely have something out of balance. It could be anything. Hard to diagnois on here. A lot of times, this will end up being a torque converter or flexplate.

[85Silverado]

it's there under load and just coasting...it doesn't matter.

hey hey hey.....be nice mike..lol But seriously....i imagine this will deteriorate the drivetrain if it's the torque convertor or flexplate....will this happen quickly or over time....i don't plan on driving her on the highway...so no more then 40mph...but she will be daily driven.....as of right now I don't have the cash to replace either of those....how can i check if it's either of those things mike?

[swervin ervin]

I was only offering some suggestions. I hope it isn't one of those. It does happen though, and it will act just like you describe, especially if it's the flexplate. I know a guy over at Chevytalk complained about his vibrating about like what you say yours does. He checked it by removing the dust cover on the tranny. I think he started it up while under it watching to see how it looked. If it has any run out at all, I think this would cause it. While in there, check all the mounting bolts for the flexplate and converter, to make sure they are tight.

There are a lot of other things that can cause this, but from what I've found out, the flexplate is a big contributor. Of course there's the harmonic dampener, driveshaft, rear end, etc. It is real tough to figure out something like this in front of a monitor, you know?

Good luck with it.

[85Silverado]

I completely understand it's almost impossible to diagnose infront of the monitor. I wish one of you guys lived in Wisconsin....I haven't noticed anyone from here yet..hehe I'm gonna check the things you suggested mike....I'll let you guys know what i see. Thanks again.

[85Silverado]

Ok, went out and listened again while driving. Got up to 45mph and the vibration was there...let off the gas...still there.....shift to neutral...gone...smooth ridiing..put it back in gear..vibration was back...it seems to be more harsh when on the gas and definately keeps up with engine speed. I hope this helps a little with helping me figure out what the problem could be

[swervin ervin]

Well, this makes me think it's tranny related. If it were driveshaft or rearend, it would still do it in neutral, right? So now the question is, what or where is it doing it at? I think the flexplate is out. TC maybe? Internal bearings in the tranny maybe? Since it has to be in gear to do it, if I were guessing, I would say TC. It is a guess, but this is where I would start if it were me. The TC will most definetely cause this, for sure. Now I'm not telling you to start tearing it apart, but depending on how bad it is, it will quit doing it one of the days, on it's on, if you know what I mean.

But, don't take my word for it, because I would hate for you to pull the tranny and swap converters and it not fix it. Use your best judgement on this. How many miles are on the tranny/converter? Usually a pretty good sign of how good a shape everything is in. Also, it's real possible it's something internal in the tranny causing it too.

Again, just some suggestions for you to think about. You might think about going by a good tranny shop and let them drive it to see if they think the above things could be it. They will be able to tell you more than I could about a auto tranny.

[85Silverado]

The tranny and engine have 106k on them...and i was told she was a work truck all her life. First gear whines like when you drive right away when cold all the time so it might just be tranny related...I'm gonna have to take it to a shop...you think i should?

[swervin ervin]

Yeah, find a good tranny shop and let them drive it to see what they think. I'm sure they have heard of this before. It's worth a shot just to see what they say.

[Hooter]

hey is your truck a 4x4? could your hubs be locked then. I know when my fords hubs are in the truck vibrates because the drive shaft has a dent in it

[85Silverado]

nope...no 4wd

[79Silv4x4]

I had a similar vibration this weekend and it turned out to be the u-joints.

[bigd65]

trust me take Mike's advise, let the tranny guy drive it and see what he says. i should ahve done this before my tranny exploded

[MOUSE]

YOU HAVE A CRACKED FLEX-PLATE!!!!!! i went through 2 before i found the real prob....which was a u-joint CAUSED by crappy pinion angle.......