Update — driveshaft balanced with new universal joints and slip-yoke. Wrong yoke had been in there for a long time. New correct yoke for the Fordomatic was over 2" longer than the one that came out. Suspect it was for a 3 speed. Anyway, with that solved a new output shaft bushing & seal got everything wrapped up. No more noise!


Did some crude measuring with a stand and caliper measuring on the outer lip just inside where wheel weights go. Runout is as follows:

LF — .026”
LR — .079”
RF — .027”
RR — .025”
Obviously that left rear is the most concerning. I made a video of the inside of the wheel showing some concerning brake drum movement. If you watch closely, the inside lip of the drum appears to be moving in & out. I checked the axle flanges with the drums removed and didn't notice any runout. Is it possible the drum is tweaked somehow and causing that excessive runout? Thoughts?
Video here

Kent — Round Rock, TX
'56 F-100  | '56 Crown Vic  |  '57 Fairlaine 500  |  '57 Thunderbird

I don't know what I'm talking about but...

One time when I was having new tires installed on my truck, the guy doing the work got me to come look at something.  On the balancing machine, the wheel appeared to be wobbling.  What it was is the bead was, for lack of a better word, wavy.  I would guess that it was at least 1/16".  These wheels had been used for the previous 10 or 15 years and were never a problem in practice so I told him to continue and all was fine.  Whether that was a smart decision, I don't know.

RE the brake drum,that outer edge is not the most critical portion so I would imagine that it does not need to be exactly concentric.  The only machined portions are usually the the braking surface and axle mating portion.  Those should be flat and concentric


Lawrenceville, GA

Thanks, Charlie. Yeah, that makes sense on the drum. What got my attention is the other side isn't showing any runnout and that drum isn't showing any movement in/out on the back side. I think pulling the drum and mounting the wheel without it will reveal if there's something wrong with the drum. Thanks!

Kent — Round Rock, TX
'56 F-100  | '56 Crown Vic  |  '57 Fairlaine 500  |  '57 Thunderbird

I think pulling the drum and mounting the wheel without it will reveal if there's something wrong with the drum

Remove the wheel, secure the drum to axle flange with two lug nuts and watch for defection. If you remove just the brake drum, reinstall the wheel to check for wheel deflection and hit the brakes, you are going to have a mess on your hands (if I am reading your post correctly).

Most likely the drum is warped and/or off-shore.

____________________________

Good point, Kultulz. Been there done that! I just cut the ignition and let things slow themselves down doing this sorta stuff.

There's no visible deflection with just the drum in place. It's pretty clear at this point it's either an axle shaft, drum or wheel. Hopefully the drum as that would require the least amount of trouble to replace. Will get post back findings.

Kent — Round Rock, TX
'56 F-100  | '56 Crown Vic  |  '57 Fairlaine 500  |  '57 Thunderbird

By noting the frequency of the vibration you should be able to narrow it down between engine/driveshaft or tires/wheels

With the tire/wheel removed does the drum center fit tight on the axle hub purchase? To me thats the most important thing.
Also I have a parts store that still turns drums. I you have one near have the put the machine an look at it with him spinning it.
Next is applying the e-brake tight when the drums are hot will distort them. A test is to slowly apply the emergency brake while coasting in neutral at about 35 mph and see what it feels like. Should be pretty smooth.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Center of both rear drums do fit nice and tight around the axle hub. I'll try the ebrake test and see what happens. Probably would be best to see if I could have them turned and watch the process. Thanks!

Kent — Round Rock, TX
'56 F-100  | '56 Crown Vic  |  '57 Fairlaine 500  |  '57 Thunderbird

Just to update this; the tires were the issue. New ones completely solved the vibration. Got the car up to 80 mph and feels great.

Appreciate everyone's help. So glad this is fixed. Now on to the next thing!

Kent — Round Rock, TX
'56 F-100  | '56 Crown Vic  |  '57 Fairlaine 500  |  '57 Thunderbird