1/2 Ton Rear Drums with Part Numbers
 

I just completely replaced my rear brakes and thought I would share the part numbers in case anyone is looking for them. My specific vehicle is a 1972 K/5 Blazer, but this should work for any 1/2 ton.

Brake Drums - GM 89058331 / AC Delco 18B471
Brake Shoes - GM 19307571 / AC Delco 17280B
Brake Spring Hardware Kit - AC Delco 18K1597
Brake Adjuster (left) Raybestos H1530
Brake Adjuster (right) Raybestos H1531
Brake Spreader Dorman 21149

There were a couple of small things that weren't included in the hardware kit, particularly the brake adjuster return spring (the one that goes between the adjuster and the inside of the shoe). The drums are a more modern design than the original ones (see pictures) but the dimensions are exactly correct and they fit inside my rally wheels. The brake spreader is a little bit wider than my stock one, but it fits perfectly. It's nice to have rear brakes again.

Re: 1/2 Ton Rear Drums with Part Numbers
 

Thanks for the info.

I believe the rear drums on 1971-72 trucks were finned originally. The 11"x2" drum on the left is the same smooth drum with the anti-chatter spring that my 1970 Blazer came with and still has.

Re: 1/2 Ton Rear Drums with Part Numbers
 

Original GM part number for the non-finned 11"x2" rear drum for 1964-70 GM 6 lug pickups/Blazers is 3846271 in the 6/71 parts book.

Per the 9/79 parts book, the finned 11"x2" rear drum is GM 3989543, and that book lists that number for 1970.

Re: 1/2 Ton Rear Drums with Part Numbers
 

Aren't the Finned Drums deeper? Like they require an 11x2-1/2'' Brake Shoe?
I cannibalised the 12-Bolt Rear End from my '67 K/10 Suburban for my '71 K/1500 GMC Jimmy about 15 years ago, and ran into the finned drums for the later axles. I upgraded to the wider shoes as well.
The '67 had been rebuilt with an Auburn Posi. The GMC had a factory Eaton Posi.
Prior to the modification, the '67 K/10 had the same drums on the rear as my '68 C/10 Stepside -- smooth [with spring around] and 11x2''. The C/10 has these drums on all four corners. The '67 K/10 had special 4x4 drums with a bigger center hole diameter for the closed-knuckle Dana 44. They were hard to get in the 1990s.
We were able to get the narrower 1967 rear end under the '71 Jimmy, but could not get the wider 1971 rear mounted properly under the '67 Suburban. It's been stored with it's rear end jacked up since 2010.

Re: 1/2 Ton Rear Drums with Part Numbers
 

According to the NAPA online site:

1970 rear drums are smooth and carry NAPA part number ND4401071

1972 rear drums are finned and carry NAPA part number ND4401200

Both 1970 and 1972 use the same part number for the rear brake shoes TS280
and for the brake hardware kit UP2202. :smoke: