Difference Between Big Bearing and Small Bearing Rear Drums?

[bulletpruf]

Fellas -

I have a rear drum setup that I picked up used a year or two ago. I don't recall whether they're supposed to be for a big or small bearing 9".

I'm assuming the backing plate is different. If so, is there a measurement that I can take to determine which I have?

thanks,

Scott

 

[EPB72]

Pretty sure the backing plate hole the axle slides through is different size large bearing about 31/8 and small 27/8 off the top of my head ?

 

[Viperwolf1]

Look at the mounting bolt pattern and size.

 

[Rustytruck]

there was a chart on this site that had the backing plate part numbers.

 

[Viperwolf1]

there was a chart on this site that had the backing plate part numbers.

Bendix 319130L or 317363L = '66-'75 big bearing/11"x1 3/4" brake , driver side
Bendix 319130R or 317364R = '66-'75 big bearing/11"x1 3/4" brake , pass side
Wagner FF55264 or L55264 = '66-'75 small bearing, 10" brake, driver side
Wagner FF55265 or L55265 = '66-'75 small bearing, 10" brake, pass side
Bendix 80174L = '74-'75 big bearing/10" brake, driver side
Bendix 80175R = '74-'75 big bearing/10" brake, pass side
Bendix 3203097L = '76-'77 big bearing/11"x2 1/4" brake, driver side
Bendix 3203098R = '76-'77 big bearing/11"x2 1/4" brake, pass side

 

[Rustytruck]

thank you viperwolf1 i was pretty sure it was your chart.

 

[bulletpruf]

Ok, the brakes/backing plates I have are the 11" x 2.25" '76-'77 big bearing.

If that's the case, these will have to go on the '72, not the '68 or '69. That's assuming the
'72 rear is original. If it is, it should be a big bearing since it's a U152 - the HD version. The backing plate bolt pattern appears to be the same, so I should be good.

Really appreciate the detailed input.

Scott

 

[Viperwolf1]

Ok, the brakes/backing plates I have are the 11" x 2.25" '76-'77 big bearing.

If that's the case, these will have to go on the '72, not the '68 or '69. That's assuming the
'72 rear is original. If it is, it should be a big bearing since it's a U152 - the HD version. The backing plate bolt pattern appears to be the same, so I should be good.

Really appreciate the detailed input.

Scott

If all this is correct you will still need 76-77 axles to use those brakes. The brake offset is different from 66-75 HD axles and 76-77.

 

[bulletpruf]

If all this is correct you will still need 76-77 axles to use those brakes. The brake offset is different from 66-75 HD axles and 76-77.

Ok, now I'm confused. I have the entire '76 - '77 assembly - backing plates, drums, shoes, e brake cable, etc. Are you saying that I cannot swap this onto my '72 diff, even if the bolt pattern is the same?

Thanks

 

[Viperwolf1]

Ok, now I'm confused. I have the entire '76 - '77 assembly - backing plates, drums, shoes, e brake cable, etc. Are you saying that I cannot swap this onto my '72 diff, even if the bolt pattern is the same?



Thanks

Correct. You would need the 76-77 axles. The brake offset is 3/8" bigger on those axles. That is the distance between the bearing and axle flange.

Other than that the axle housing itself should be the same dimensions.

 

[Jdgephar]

See my thread with my issue. I had big bearing 76-77 axles on my '72. Backing plate, shoes and drum for a big bearing '72 did not work. Ended up using a later model backing plate from a spare axle that I had and using all 76-77 parts.

https://classicbroncos.com/forums/showthread.php?t=299238

By the way, I still have all of the '72 big bearing parts (backing plate, new shoes, drums, etc.) if you would like them. My '72 had 76-77 axle shafts and I converted to all 76-77 parts.

 

[bulletpruf]

Correct. You would need the 76-77 axles. The brake offset is 3/8" bigger on those axles. That is the distance between the bearing and axle flange.

Other than that the axle housing itself should be the same dimensions.

Thanks for the explanation. I appreciate it.

See my thread with my issue. I had big bearing 76-77 axles on my '72. Backing plate, shoes and drum for a big bearing '72 did not work. Ended up using a later model backing plate from a spare axle that I had and using all 76-77 parts.

https://classicbroncos.com/forums/showthread.php?t=299238

By the way, I still have all of the '72 big bearing parts (backing plate, new shoes, drums, etc.) if you would like them. My '72 had 76-77 axle shafts and I converted to all 76-77 parts.

I'll send you a message on the '72 parts.

Thanks,

Scott