I was just out in the garage doing what you suggested.

Right side: .005" near end of taper and .004" on thicker end near backing plate.

I could look at this one of two ways...

1) The left side is out by roughly twice the amount the right side is out

...or...

2) The left side is only out .004" to .007" more than the right side. For perspective .007" is about 1/128".

In the strictest sense, it comes down to what the specification allows. In a practical sense, I would think a bent axle shaft would transmit some vibration or other unwanted sensation into the car and my Clipper rides, steers and brakes quite nicely with no unexpected shakes, rumbles, etc. except for the grinding.

O_D

Funny you mention the axle shaft runout as I did check it but couldn't find any reference spec in the manual with which to compare my numbers.

At the end of the taper I measured .012" runout and near the thicker end I measured .0085" of runout. This is with new outer Timken bearings, races and seals-I have no idea the runout with the old bearings which were in service when my problem first arose.

Regarding my measurements...I am not machinist and am working with a Harbor Freight dial gauge and an old magnetic stand that I inherited from my grandpa (who was a machinist) so my results may not be the best.

Also, here's the short version of the backstory:

-Bought car and drove it regularly for a year or so. It was regularly maintained by the previous owner.
-On a weekend drive I noticed a grinding from the left rear drum at braking speeds of 25-30mph. Brake performance was not affected.
-At this point I had never had the rear brakes apart so I adjusted all four brakes and hand brake and nothing changed with the grinding.
-I replaced all hold-down hardware and return springs and nothing changed with the grinding.
-I replaced rear axle shaft bearings, races and seals and reset the end clearance to .0045" (using a dial gauge) with a shim stack of .024" on the right and .020" on the left. Again, no change with the grinding.
-I disconnected the hand brake completely to eliminate possible misadjustment. Still no change in the grinding.
-Today, one of the last shops around me that will turn drums looked at the drum and didn't find anything wrong. He turned it the absolute minimum just so I could definitely rule it out as the culprit. Of course, it rained this afternoon and, as a matter of prudence, I just won't test brakes in the rain. So here we are...

Don - It's a '55 Clipper Constellation. The junior brakes for that year measure 2" wide with 3/16" thick friction.

Mine are definitely not original but do fit the car. I took a variety of measurements on both shoes and they vary in width between 2.000" and 2.053" for the primary shoe and 1.996" and 2.055 for the secondary shoe. At least to my eye the width in excess of the 2.000" specified by Packard seems to be the small "lip" of the steel backing that extends outboard beyond the actual friction width. I will say the shop that turned the drum suggested I might have to consider carefully removing that lip with a grinder to ensure full clearance.

I also measured friction depth on each and found the primary shoe ranged between .176" and .210" and the secondary between .145" and .224." While I don't know the exact age, they definitely do not have much wear on them.

Also, because I noticed that the end section of the primary shoe displayed a slight trapezoidal shape, and in an effort to drive myself completely mad, I compared friction thickness at various points of each shoe at both the inboard and outboard edges of the shoes and found deviations in thickness (side to side) on the primary shoe from .008" up to .020" and, on the secondary shoe, from .008" to .017". So they were not wearing evenly but I don't think the uneven wear was great enough to cause any problems...although I'm happy to hear what others might think.

All good thoughts.

I just had the drum checked by a one-man shop that comes highly recommended for drum brake work. He said the drum checked out within specs but ran it on the lathe (which was older than my car) to "clean it up" and help eliminate one more potential question mark.

He also suggested pulling everything apart and checking for burrs or any other damage on the shoes or backing plate. After seeing the rubbing on the drum, he indicated that the actual contact was relatively minimal (although certainly loud and annoying) and that the answer would likely lie with a problem "measured in the thousandths."

If none of the above works, I'll swap the drums and see if the problem moves with the drum or stays with the axle shaft.

Quote:

This has been in the back of my mind as well. Over 70 years a lot of different people have been in and out of these brakes.

What I can't figure is, if this were to be the case, why were the brakes fine for so long? Maybe I'm thinking about it wrong, but with the force the hub seats onto the axle, I would think that, if the hub seated too deep onto the axle, the grinding would show up immediately at the time of reassembly. In my case, I bought the car and drove it without ever opening up the rear brakes for more than a year with no problems.

Quote:

That really sums up what is so maddening about this. Basically the brakes were fine and then they weren't. I tried adjusting them, then replacing all the hold-down hardware and return springs, then checking axle bearing clearance (with new bearings and seals), adjusting everything again, and, most recently, disconnecting the hand brake just to make sure it wasn't pulling things out of place. So far nothing has changed the nature of the grinding one bit. At least if I had put something together wrong I could blame myself and then fix the problem.

Quote:

Interesting thought. The grinding started about a year after I bought the car. During that first year I drove the car frequently with no problems and, until the noises started, I had never taken the rear brakes apart so if something didn't fit right it was like that before the grinding started. Also, when I performed the rear axle service I cleaned the axle flange and the backing plate and installed new shims. None of that changed the nature of the grinding for better or for worse.

As for a bent backing plate, I can't think of anything that would have caused damage to the plate in my first year of ownership. Again at the time the grinding first began I had never taken the rear brakes apart.

Quote:

The problem is only on the left (driver's side) rear brake.

Still no luck. I completely released the hand brake tension at the equalizer (fully slack) and made sure that the rear service brakes were adjusted and then took her for a spin with the exact same results as before: grinding at braking speeds of 25-30 mph or above. The braking behavior was normal and pulled the car down steady and straight.

My thinking in leaving the hand brake essentially disconnected was to isolate potential mis-adjustment in the hand brake and ensure that nothing would impede the shoes from seating on the anchor pin. And then I hoped for the best but to no avail.

Attached are pictures that I took after my latest test drive. You can see the "polished" edges of the shoes with the heaviest contact occurring at the bottom of the secondary shoe and lighter contact at the top of the primary shoe.
The second picture shows the "polished" rivets on the underside of the drum. These points of contact do not seem to be getting any larger, if that makes a difference.

Again, I'm open to any thoughts. The shoes are probably the next suspect although I'm not sure how to identify a slight twist as they pass a visual inspection. After that, I suppose looking at the drum for warp is next.

Attach file:

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  Drum1.JPG (200.88 KB)


  Drum2.JPG (286.95 KB)


  Drum3.JPG (194.01 KB)


  Drum4.JPG (271.68 KB)

Thanks Ross.

I used your procedure to adjust the rear service and parking brakes after reviewing your youtube video. (Your approach to the parking brake is much more straightforward than what's in the manual.) I'll reset everything tomorrow and then re-adjust and try again. Maybe I'll get lucky.

One question though...would slackening the parking brake cables and then going for a test drive prove anything about how the shoes seat on the anchor pin? In other words, would this help isolate the cables as the culprit in case that I'm not adjusting them quite right?

Maybe I have my terminology wrong.

According to the 1955 service manual, after installing the shims "the clearance should be .004"-.007." After installing the new bearings, races and shims and seating each against the opposite backing plate, my final measurement (taken with a dial guage-not the adjustable tool) was .0045." That is what I referred to as end-play.

The thought of excessive axle movement is an interesting one. If the axle were moving too much, I would think that the unwanted contact would be more evenly distributed on the shoes. In my case, only the bottom 1-2" of the secondary shoe show any sign of making contact with the drum. Also, this started happening before I changed out the rear axle shaft bearings. While it's certainly possible that I replaced an out-of-spec rear axle adjustment with another out-of-spec adjustment (and attendant new parts), I'm not sure my luck is that bad.