rear suspension thunking

I have a thunking noise (as in harsh rear suspension) when going over seperations/cracks in the road. not like a metal to metal sound, but like a zero rebound dampning sound. pushing on the car the shocks seem firm and ok. tires are at 34psi. any ideas?

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77911s

Somebody jus has this issue on www.rennlist.com.

I believe they called it a "POINK"!

Check your rear (anti-) sway-bar mount. This is difficult to do (for the driveway mechanic anyways).

You need a buddy, drive the car over a bump,(not your buddy :-/) so one rear tire moves up and the other three don't. Have your friend in a good position to look at the sway bar mount(s), if they move, the mounts are probably broken. Apparently they do and will break with heavier sway bars.

Good luck!
Nick

If the rear swaybar mounts are cracked or broken, it is usually very easy to see. I would just jack the car up and carefully inspect the swaybar mounts. If they are cracked, you should be able to see this quite plainly.

Brian

I had a similar problem - it was indeed one of the sway bar mounts in the rear. I was definitely able to see the problem just by looking under the car and feeling around with my hand. If it's clunking I would guess that the mount has separated from the body of the car. I'm sure you can buy the mounts somewhere, but I just had a local race shop fabricate a pair and weld them in.

ok the swaybar mount etc. are all intact...had a good look under there and apart from broken shocks...I dont know what it could be. I hear nothing over crests/dips but on choppy stuff it really sounds like something is thunking. never broke a shock before, so ???

Check the upper mounts for the rear shocks ... and the rear wheel/tire for lateral 'play' at the top of the tire: grab the top of the tire and try to rock back and forth. There should be NO noticeable play!

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Warren Hall
1973 911S Targa

ok after inspection of all the advised areas (thanks all) all is good.. no swaybar probs, no shock mount probs...I have searched and tightened!!! though today something odd... going down the road at say 50-60 not accelerating, but just maintaining..(also at speed in neutral) theres the same noise, only repetitive and much fainter...then loud only when I hit choppy bumps...could it be the CV joints?

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77911s

Well, CV joints can make various 'odd' noises, and since your problem persists, I suppose the thing to do is remove, clean, and repack them! I'm sure they need it if you haven't done it in the last two years or so! If you have never done this before, it might be helpful to go to a library and get one of the Robert Bentley manuals for a VW Beetle, Bus, or Type 3, as those manuals have a very comprehensive section on disassebly, cleaning, diagnosis, and repacking of CV joints. A very high-quality Moly grease is needed, not just whatever is available at the local Sears or K-Mart, so I recommend the SWEPCO Moly grease that Pelican has, and two tubes will be needed for 4 CV joints! You will need 4 new CV-joint gaskets, too! Close inspection of the CV-joint boots for any cracks would be a good idea, too, so you can order any replacement boots, before starting, along with the gaskets and grease.

Careful removal of the Allen bolts on the CV joints requires checking for any build-up of dirt or gunk in the bolt heads, and cleaning out with Q-tips and solvent, before any damge is done to the bolt head!!! If there are serrated washers under the Allen bolts, make sure you get each washer off with each bolt, and don't lose any! Be sure to apply your handbrake securely before removing any of the CV-joint bolts, and be sure to start with the inboard Cv-joint, then the outboard one! Reverse the order when installing, tighten outboard joint first, then inboard. Be sure to mark or tag each CV-joint before removal, left inboard and outboard, right inboard and outboard, and put back in the same place they came from. Any pitted or dark, discolored ball bearings can be replaced at a local bearing supply house, as the sizes are standard, and I have done that on both VW and Porsche CV's successfully. You will, of course, want your car up on jack stands for this job, securely placed under the torsion bar tubes, just inboard of the swing-arm 'castings' on the ends of the tubes. And, a torque wrench is required for installing the Allen bolts when you are ready to put the CV-joints back on! Good Luck!

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 02-14-2000).]

Is this man not a walking encyclopedia of amazing knowlege?
thanks Warren!

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77911s

Hello;

Did you check your torsion bar bushings. Look at the cover if the bar is not sitting in the center of the cover they need to be replaced. -andy