What’s causing that “wook-wook” sound?

Question:

When I bought my 39,000-mile original 1965 Corvair a few months ago it stopped well, but made a “wookwook-wook” sound when braking and felt like a brake drum was out of round. Even though the linings looked new, I had a local shop replace all linings and turn all four drums.

After a few miles the problem came back. I’ve worked on my own brakes for 50 years but have not seen anything like this. The shop does not seem to know what to look at next. Do you have any suggestions?

Answer:

I would pull the brake drums and make sure that they were properly centered when they were resurfaced, and that none of them are warped, because that is the most likely cause of such problems. A dragging brake shoe can heat up a drum and ruin it, as can extended braking on a long downhill run. I would also check all of the linings to make sure no wheel bearing grease or other contamination has somehow gotten onto the linings.

If the run out of the drums is good and the linings are fine, I would take a look at the rear half shafts and wheel bearings. Corvair rear wheel bearings can go dry after years of service, and there is no way to grease them except to tear them down and rebuild them. It is a bit of an onerous job, but there are shops that can do this for you.

I would also make sure the universal joints on the half-shafts are properly packed, properly oriented to one another and in good shape as well. A stiff universal joint could cause such a noise. Also make sure that the A arms and suspension that holds the wheel hubs in place are aligned properly and not bent or pushed out of position.

Finally, it is possible that a backing plate has been tweaked in an altercation with a curb, and it is even possible for a half shaft to be bent or twisted. I have seen it more than once on conventional drive shafts because of improper lifting of the car on a lift.