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burninator

Rear end vibration

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Posted (edited)

Something in the rear of my 240 is vibrating like crazy at highway speeds. I checked the axels for play and changed out the one that felt marginal. I also swapped out the wheels and hubs to spares from my old car. It still makes the noise.

 

Keep in mind, my old car was an autocross only car, so I never went that fast in it, not for any amount of time, and I was always racing, so I might not have noticed if it had a slight vibration at the higher speed sections. But I don't think it had a vibration.

 

How likely is it the diff is causing the vibration? How can I tell? What else should I check?

 

 

 

 

As a secondary issue, at low load like maintaining speed, or just when you stop accelerating and start to let off, but not decelerating, there is a whine from the transmission/clutch area of the car as near as I can guess. What should I look at there, is it something to worry about?

 

*Edit - Meant to post this in the troubleshooting forum. Sorry.

Edited by burninator

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All of the vibration issues I've encountered were fixed with either u-joints or tires. Anything is possible. Shouldn't be hard to pop the back cover off and give it a visual. Just put a jack under it, take the mustache bar, and cover off. It's been a LONG time since I've seen an unmodified set-up so I can't remember if there's anything else in the way.

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Do you feel the vibration, or hear it?  Or both?

 

Under what conditions do you notice the vibration?  Just cruising at highway speeds?  Is it worse under load (either acceleration or braking)?  A "no load" vibration indicates something out of balance (e.g. driveshaft or half-shafts).  A vibration under load might be due to worn bushings in your LCAs, mustache bar or differential.

 

One way to isolate the source of the vibe would be to have someone else drive, while you crawl around the hatch with a stethoscope.  

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I feel the vibration and hear it. It's only at speeds above 60mph or so, and it happens all the time whether accelerating, maintaining speed, or decelerating. Even if I take it out of gear. The vibration seems to be coming from behind me.

 

I've seen driveshafts with weights on them, they can be balanced at a shop right? Can half-shafts also be balanced, or would it need to be replaced? I swapped one half-shaft already to one I think is good. I could just swap the other and see if it changes. I also have a spare driveshaft and diff, I didn't want to just keep swapping parts to ones I only think are good without knowing what the issue is.

 

I'll check all the mounts and bushings, just to be sure. But sounds like the driveshaft or half-shafts are probably the issue. Maybe I should grab some new u-joints for when I'm swapping parts.

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Swap your wheels front to back.  See if there's a change.  I had a broken belt in a tire that caused a vibration.  Autocross is hard on tires.  And rims if you hit something.

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