This has got me puzzled....

Bassman/NZ

Bassman/NZ

Well-known member
Just discovered that my brake drums are loose on my rear end, even though I have them torqued up to around 200lbs/sq.in. It's a 47 car rear, fitted with 47 pickup brakes and drums, and I lapped the drums to the axles with valve lapping paste. I can grab hold of the tire and rock it, and I can see, and hear, the drums moving in relation to the backing plates. Aaarrrgghhh!!!!
 
Inch pounds or foot pounds? If drum is bottomed out, it won't go on any farther no matter how much you tighten it.
 
If the drum is bottomed out....
Yep, that's what it seems like. I cant figure out why it would be bottomed out. Maybe I need a couple of those axle shims the Model A guys sometimes use.
 
Sounds like it's bottoming out on the woodruff key and not seating on the taper.
Try mounting the drum to the axle without the woodruff key to see if that corrects the problem. If it does then the woodruff key is too big.
 
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It might be that the axle housing bearing journal is worn.

No matter where the drum is bottoming, it should never "rock" back and forth, with hand movement, when torqued to 200 ft. lbs. I think you might want to look elsewhere.
 
JWL said:
It might be that the axle housing bearing journal is worn.

No matter where the drum is bottoming, it should never "rock" back and forth, with hand movement, when torqued to 200 ft. lbs. I think you might want to look elsewhere.
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If I slide the bearing onto the journal I can rock it a little. Should it be a relatively tight fit?
 
51 MERC-CT said:
Sounds like it's bottoming out on the woodruff key and not seating on the taper.
Try mounting the drum to the axle without the woodruff key to see if that corrects the problem. If it does then the woodruff key is too big.
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Tried this, and the problem decreased a bit. Going to try some bigger flat washers, because I noticed the shoulder on the axle at the end of the thread is level with the end of the hub. The existing washers may be tightening up against the shoulder.... maybe.
 
Brgs typically move a little bit especially if you're looking for it. I'm guessing there's a washer with a center diameter slightly bigger than the thread diameter and smaller than the start of the axle taper that the nut goes against. That washer may be bottomed out against the shoulder of the axle.
 
Dave72dt said:
Brgs typically move a little bit especially if you're looking for it. I'm guessing there's a washer with a center diameter slightly bigger than the thread diameter and smaller than the start of the axle taper that the nut goes against. That washer may be bottomed out against the shoulder of the axle.
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Just picked up a couple of 1" hardened flat washers, so I'll give that a try before anything else.
 
If the axle has sheared the key sometime the axle will be twisted and with new key will not seat properly
 
Well, I tried using the bigger washers to no avail, so I guess the problem is either the bearings or the journals.
 
I'm not sure what the bearing would have to do with the ability of the wheel to "rock". If the bearing were excessively loose, you would only have radial movement of the wheel. If the hub is up tight on the axle, there can be no rocking. It sounds "to me" like the fit between the axle and the hub are where the problem exists. With 200 ft lbs of torque, it should pull up OK providing the key is not wrong and the shaft is not distorted from a shearing of a previous key.
 
marty are you sure its not in the key way? 1 of the groves for the pin might be worn they are sometimes sloopy & that can cause your problem did you get fan belts ok,,im now up in washington state if you still need trev:)
 
Thanks Trev, I found the perfect belt, a Dayco B25.
This is perplexing. When I visualise this thing in my mind I cannot see any way for the hub/drum to rock unless it was loose on the taper. The keyways in both taper and hub appear good, straight undamaged walls, and the keys are new. I will do a more comprehensive lap-in and see what happens.
Incidentally, when I put this rear end together (47 car banjo, torque tube and bells, 47 pickup axles, brakes, hubs/drums) I discovered the axles both had "Made in Germany" decals on them. Weird!
 
When you are lapping the drums and axles look at the polishing pattern. It may be that the taper on the axles does not match the taper on your drums? I've never heard of this before.
 
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