Thumping might have been a better description than clunking. BUT I think I determined what it was. First, a summary of what happened.

- Friday, April 1 - Mother Nature plays a trick on us and we get 6+" of very wet snow. Nuisance snow as I refer to it; with the temperature slated to be in the 40-50's the next 2 days, I skip shoveling. But I do push the snow off the top and rear of the sedan. It was so wet it just slide off and piled behind the car.

- I turned the car over and drove over the now snow hump behind my car. I then drove ~3 miles and parked the car for about 4 hours. The temperature was just above freezing.

- I get back in the car and within .5 miles I get the thumping, then a single pop and the thumping continues the rest of the way home.

- I get home, remove rear wheels and check underneath. Nothing stands out, thus my initial note.

- I drive the car ~2 miles around the neighborhood and only hear the thumping once.

- The next day, determined to find the problem and having some initial feedback from my note, I go for a 25 mile round trip drive. Initially, I hear the thumping/clunking, but not as continuous. And it slows down after about a mile, maybe happens a few more times in the next mile or two. And then no sign of the noise for the next 10 miles.

- I return later that day, and again, no noise - just as I now expected.

- I drive the car this am for ~30 miles and again no noise.

So what was it?

My theory is that the snow I slide off the top and rear of the car was just high enough that when I backed down my driveway, a good incline, my tailpipe went right into this 'snow bank' and clogged the end of the tailpipe. Then only driving 3 miles, there was not sufficient time for it to melt off.

While not freezing, the tailpipe was still clogged when I went to drive away 4 hours later.

So possibly I now had an ice ball in the end of the tailpipe close to the muffler end that was rattling around. It finally stopped rattling around when it melted by the next day.

Now for the pop - possibly that was the exhaust blowing through the clogged tailpipe.

Any thoughts or comments on my theory? And if it makes sense, what is the physics behind it?

Thanks all for your feedback.

The word 'Clunking' usually points us to Torque rod Bushings. Clunks at slow starts and over speed bumps at slow speeds.

Hearing a pop and clunking, I am wondering if your E-brake Pads have let go and are bouncing around in the Drum area of the Rotors.
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Hello,

Most likely that is the back of the rear brake assembly tapping your inner wheel well. Caused by worn out Trailing Arm Bushings that allow the rear axle to move when you take off. Very common problem on these cars, the cars outlast the life of the bushings. The car will drive just fine and the only other symptom I had on my 86 was a slight roaming sensation at higher speeds. Nothing dangerous, but you sort of gently and slowing moved from side to side.

Replaced Inga's with Poly Bushings using the hole saw method. Been almost three years and over 60K miles and problem solved.

Regards,

Paul

How about a loose top strut bolt? Or are they replacement shocks? Some of them are made with too much clearance.

I would also see if taking off and putting on the wheels affects it. That's all you did right? How about setting the E-brake? Could the shoes have been catching somehow?

Good Luck

Some things that can make knocking sounds:

sway bar mounts, there is a bolt and a clip at each end.
shock bushings, especially the bushing the cross bolt passes through.
exhaust to axel clearance, this will change as the axel drops down.
trailing arm bushings, look for chunks missing around the edges.
U-joints, with the rear wheels off the ground put the trans in neutral and turn the rear wheels back and forth so as to turn the driveshaft.

Is the repetitive clunking regular like a clock or a wheel turning?
Is it associated with small bumps in the road?

Hi,

Your rear suspension bushings are in good shape?

Maybe check to see if any of the exhaust is close to the body.

Travis