Packard Forum Index » V-8 (1955-56)

TxGoat offers a good clue about what the problem may be. I would recommend replacing the axle if the drum switch does not work.

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.

I’ve lost track of what year and model the car is but is it remotely possible that they are junior shoes in a senior car? I’m not sure if it would make a difference but i seem to recall the senior shoes are wider.

Sorry, I haven't read thru the entire history of this problem, but have you ever checked the axle shaft for run-out?

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.

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...

I'm not aware of a specification or what run-out might be typical, but to put your results in some perspective you might check the opposite side shaft and compare.

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.

It looks to me like your brake drum is slightly too far inboard when mounted and tightened. That could be due to the fit of the hub to the axle taper or to the location of the axle shaft.

I assume the axle shaft is located by the wheel bearing.

Is there any chance that the wheel bearing is either off-spec or not seated properly in the axle housing?

Is there any chance that the location of the inner wheel bearing race is not properly located or seated on the axle shaft?

A bent axle or other run-out situation might or might not cause vibration to be felt in the car, and it would probably do so at some particular speed range, if it did it at all. That kind of interference might cause an intermittent grinding sound instead of a steady grinding sound.


An incorrect fit between the axle taper and the hub is a fairly common problem on older vehicles or vehicles that have had parts replaced.

If the hub, for any reason, goes too far onto the axle when properly tightened and seated, it could cause your issue.

The hub or axle taper, or both, or some issue with the key or keyway can cause problems.

Swapping brake drum/hubs left for right might improve the situation.

Otherwise, if everything works well except for the slight brake shoe to drum face interference, I'd consider carefully grinding off about 1/32" or a little more from the outer edge of the brake shoes.

I'd do it with the shoes mounted.

A 4" right angle grinder might be handy for this.


DON'T BREATHE THE DUST!

I'd want to do this outdoors and I'd want to clean up all grinding dust before reassembling the brake.

Keep the grinder contact with the shoe moving to avoid heat buildup, and keep the grinder wheel contact moving along the edge of the shoe, not across it, for a better finish.

IF the drum can be removed from the hub,
it might be possible to make a shim to space the drum a little farther outboard.

I'd want to keep the shim thickness to a minimum, and it ought to be made from metal. A steel shim or two made from flat sheet metal ought to work.

A Dremel tool could be used to clean up edges and lug bolt holes so that the shim would lay flat. The shim ought to cover the entire contact face between the drum and hub.

Another possibility is that the wheel does not fit correctly and is distorting the brake drum when it is bolted in place.

The wheel may be damaged or may be incorrect for the application.


It's unusual, but in some cases, a damaged wheel or one that "almost fits" can put pressure on the face of the brake drum and cause it to flex inward.