Reverberating vibration in rear suspension?

[Insidious Surmiser]

I've got to take my turbo back off tomorrow, since the stupid feed/drain combo flange is leaking, but I finally got to put some miles on my '88, and the rear struts are definitely toast. I have some new ones to put on it, but before I dug into it, I though I'd see if anyone knew what would cause a bump in the road to be felt ~4 times. harsh reverberation of an impact... also noticed it when I took off in 1st once.

 

[mk3supralove]

Could be faulty/over inflated tires

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[tlo86]

vibration can be many things might have to be more specific/detailed.. anywhere from your shocks trans ujoints or axles or any number of bushings heh

 

[suprarx7nut]

I've got a similar annoying resonance in the rear as well. My shocks are very old so I'm hoping that's the sole cause. It'll be tough to troubleshoot much until the shocks are replaced.

You can inspect all the rear suspension bushings and hardware as a failed bushing or loose hardware would help to make an unpleasant ride.

 

[Silver MK3]

While you are replacing the shocks torque your front and rear sub-frame bolts. I know some members had suggested this in many other threads I had read before, but I never thought much of it. I did torque them about a month ago and I was surprised how much they turned on my car which has fairly low miles, and hasn't been beat on. After this it also took away a clunking noise I would get in the front when hitting a pothole or bump in the road. I would just inspect everything while you are back there and look for broken/worn components.

 

[80083r]

Also double check the bolts holding your struts to your strut mounts (the ones on top) that can cause a rattle that sounds like the back end is coming off. Mine was loose by about 1/4 turn.

 

[Insidious Surmiser]

Well, the best I can describe it is a harsh (what feels like rubber on metal) vibration that repeats it's-self rapidly, till it runs it's course. The car does squirm some too (with the vibration), which initially made me think it was an issue with the subrame. The rear definitely squirms, but I feel as if the front may be doing the same as well, hard to tell really. I'm going to get under it tomorrow, and check it out. Today I just cleaned the car up some, put the bumper back on, and put some of the interior back together. I should've taken the turbo off, but I caught up on sleep instead (much needed)

 

[tlo86]

you feel it in the steering wheel? does it feel like the front or the back of the car is making the vibration

 

[Insidious Surmiser]

definitely coming from the rear, no question about that. I checked the rear subframe, and holy hell!! I'd need a massive tq wrench to adequately check those bolts.... they did seem extremely tight though. I only weight 140lbs and tq spec is 133, so I couldn't get that much force on it with the tools I have. I think I'm going to just change the struts out and see if there's any play in any of the other components.

and to answer your other question, no I don't feel it in the steering wheel, but it does alter the direction the vehicle is travelling a bit

 

[suprarx7nut]

definitely coming from the rear, no question about that. I checked the rear subframe, and holy hell!! I'd need a massive tq wrench to adequately check those bolts.... they did seem extremely tight though. I only weight 140lbs and tq spec is 133, so I couldn't get that much force on it with the tools I have. I think I'm going to just change the struts out and see if there's any play in any of the other components.

Yeah the sub frame bolts take some effort to torque. For a skinny guy they can be pretty tough to get to the needed 140 ft lbs or whatever it is. I had to plant my foot against the chassis and pull about as hard as I could to get it there. That's with a pretty big wrench too...

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[Silver MK3]

definitely coming from the rear, no question about that. I checked the rear subframe, and holy hell!! I'd need a massive tq wrench to adequately check those bolts.... they did seem extremely tight though. I only weight 140lbs and tq spec is 133, so I couldn't get that much force on it with the tools I have. I think I'm going to just change the struts out and see if there's any play in any of the other components.

and to answer your other question, no I don't feel it in the steering wheel, but it does alter the direction the vehicle is travelling a bit

Yeah they are tough to torque, but yours probably need it even if they seem tight. Mine were hard to get to the torque specs as well and I'm bigger than 140 lbs and was using a 1/2" torque wrench that's probably ~2.5 feet long. It is listed as a maintenance operation, but it is usually forgotten or overlooked.

 

[tlo86]

dont rule out a diff or axle or even loose lug nuts + ujoints