Help! Brakes for a 71 3/4 ton 4x4 w/leafs

[Scott McLean]

Please help me out it is killing me not to be able to drive my truck.
Here is what I have. A 1971 Chevy Custom 20 deluxe 3/4 ton 4x4 with leaf springs. I already went through and rebuilt the front brakes. Moved on to the rear brakes and to my suprise the previous owner purchased the wrong drums and placed them on the truck. These drums do not even cover up the entire brake shoe.Also the cylinders are seized no doubt from all of the debris coming into them from the gap between the drum and the backing plate. The axle is definately and Eaton with the round cover. Although I have no idea what size brake drums or shoes came originally on this rear end as the ones that are on it are obviously wrong, I do know that the depth of the drum needs to be somewhere around 6 inches. I heard that some of the ho72 came with no spins/Detroit lockers in them so I went for the test on a gravel road and both rear wheels dug wholes in the gravel which leads me to belive it is locked. I want to exhaust all possiblilities of keeping the rear end stock as I use this truck for its pulling/trailer towing capabilities. Any help?

[rage'nrat638]

i have a 69 3/4 ton 2 wd w leafs heres some pictures

napa should have the drums...they are about 150.00 each..

[rage'nrat638]

i just looked for your year drums no listing

heres the drum listed for the 69

Brake Drum -


Item#: UP 6401137

Price: $134.00
Attributes:
# of Bolt Holes:8
Bolt Hole Circle Diameter:6.5"
Brake Drum Surface Depth:2.89"
Maximum Diameter:12.06
i hope this helps at least theres some sizes to measure from

can somebody help this man here..

[DirtyLarry]

You could always hit up the bone yards and find an old Eaton axle to pirate the drums and backing plates then buy a new set of shoes and a hardware kit to match the donor trucks shoe size.

rage'nrat638, what rear axle is in your picture? It looks to be a Dana by the dimples in the hub. I have not seen a pre 90’s GM full-floating rear axle with slip off drums but then again I cannot remember the last time I played with an older GM Dana 60 fullfloater. All the ones I have messed with are either Eaton’s, Corporate 10.5 or Dodge Dana 60 fullfloaters. None of which had slip off drums.

[jerry moss]

rage,those look like dana 60 drums ?
4x4 eaton rear drums are pretty much extinct unless you find a store with some really old stock on the shelf under a foot of dust. best of luck.

[rage'nrat638]

yea i was hoping this would help him..i had a hard time.. after i ran a parts listing on his 71 and they had no listing..for drums

i am afraid my drums will become not available soon as well..
yes its a dana 60 ... it could be the best part of the truck

man i hope some has your drums..scott. you may want to do a wtb on the parts board. you might have some luck there.

i promise i will keep a eye out for these drums scott

[PICKMUP]

I think 4X4 used different drums than 2wd. Time to get a picture with exact/correct drums with all measurements and see if anyone has them. I know the Eatons had the drum & hub built as one unit $$$. I have some 2wd only.

[Jtrux]

Originally Posted by Scott McLean

Please help me out it is killing me not to be able to drive my truck.
Here is what I have. A 1971 Chevy Custom 20 deluxe 3/4 ton 4x4 with leaf springs. I already went through and rebuilt the front brakes. Moved on to the rear brakes and to my suprise the previous owner purchased the wrong drums and placed them on the truck. These drums do not even cover up the entire brake shoe.Also the cylinders are seized no doubt from all of the debris coming into them from the gap between the drum and the backing plate. The axle is definately and Eaton with the round cover. Although I have no idea what size brake drums or shoes came originally on this rear end as the ones that are on it are obviously wrong, I do know that the depth of the drum needs to be somewhere around 6 inches. I heard that some of the ho72 came with no spins/Detroit lockers in them so I went for the test on a gravel road and both rear wheels dug wholes in the gravel which leads me to belive it is locked. I want to exhaust all possiblilities of keeping the rear end stock as I use this truck for its pulling/trailer towing capabilities. Any help?

lift the rear end off the ground and spin one tire by hand, if the opposite tire spins in the same direction you have a locker. on loose gravel as you stated above it would not be dificult to spin both tires even with an open differential. Also, for about a hundred bucks you can pick up an entire 14 bolt from a junk yard that will bolt right up and it still has stuff available for it easily.

[Scott McLean]

Yes, the axle had to come out of the rear end to remove the drum. I would
guess that the proper brake drums and shoe sizes will be revealed by someone
with the exact same truck. I know this is a longshot but with these trucks getting some 36 years plus in age I am sure other owners have come across this path as well. All of the parts houses go directly from shoe size and drum inside diameter measurments. With out these measurements ordering any parts is hit or miss. Mostly miss I am sure.

[DirtyLarry]

I wouldn’t think finding a ¾ ton Eaton in an early 70’s Chevrolet would be that hard to find at the bone yard. We tripped over them all the time around this neighborhood. As I mentioned earlier….grab the drums, backing plates and old shoes from a donor so you have a matched rear drum brake assembly for an Eaton then head to the beer store on your way home after you pick up the new brake shoes, hardware kit and seals from the parts store.

Or…jtrux said, ditch the Eaton and upgrade to a 14 bolt FF but that seems a bit extreme for just a brake job let alone trying to find one with matching gear ratio to your front axle and in right price range. A lot of yards are putting the screws to people for 10.5 FF these days.

[special-K]

In`71 they used one year only brakes in 3/4t 4wds.They were real narrow,like 2" and I had a hard time finding those 20 years ago.But,I think you are in luck.It looks like you have those rare drums on your truck and they are wrong.I believe you,most likely,have a second-design`71.GM made a 2nd-design front-end that is the same as a`72.I wasn`t aware of the rears being different,but yours are.The brakes or rear may have been swapped.But,go to NAPA and ask for`72 brake parts and see what that does.I bought all parts for my`72 K/20 from NAPA.If you truly hit a dead-end,check out Blackbird`s rear disc conversion for the HO52.

[1969 GMC]

Originally Posted by special-K

I bought all parts for my`72 K/20 from NAPA.If you truly hit a dead-end,check out Blackbird`s rear disc conversion for the HO52.

You can make discs yourself for a LOT cheaper than the blackbirds kit. modify (or weld on) 14 bolt brackets, use the same calipers as the front or caddy calipers if you need an ebrake. This option cuts quite a bit of weight.

[snow man]

the brake drums you need were a 1 year thing and are not available. i went trough the same problem and put black birds rear disc kit on mine. i did save all the backing plates and drums but the drums would have to be turned too the max and i didn't want problems later down the road. hope this helps. snow man

[Scott McLean]

Alright I give in. Too many variables to get it right! So if I am going to put in a 14 bolt, are there some that would be easier to work with than others. I would like to limit the amount of alterations if at all possible. ie ( moving spring perches, shock mounts, shortening drive lines and emergency brake adjustments.
Thank's everyone for your help.

[special-K]

It would be easier to stay with the HO52.The axle is the same.You can use the other brake parts.If your truck`s original under there,check the front axle number on the right axle tube near the pumpkin.I can tell you if you have an early or late`71.If your drums are narrow and wrong,then you need the drums that are available.I don`t think it would go together with the wrong/wider shoes,if you do have the 1st design.

[Americanrider]

Was that you who posted on the local craigslist a few days back looking for Eaton drums? I would give you mine but haven't swaped to a 14blt yet. There are a few Eaton's in the local yards I know of, a 69 and a 71 both are 2wd 3/4tons. I just found them on Thursday. Shoot me a PM and we can hook up and go parts hunting. I live in South Spanaway area, Elk Plain along Hwy 7.

[Scott McLean]

Special-k the numbers on the bottom of the front axle tube are like this.

4 1 1A4 603317 8

4 7 1A8

[Scott McLean]

Yes that was my posting, I am looking down all avenues. Thank's for the part hunting offer. I might just take you up on it.
Scott

[special-K]

The numbers in the GM Parts book go like this:`71 1st design axles are stamped with either 603351 or 603352.The 2nd design axles are stamped with 603333 or 603334.I know I said these were on the right axle tube.This would be yrue if you stood facing the truck from the front.I would have been more accurate to say,"on the front of the L.H. axle tube adjacent to the carrier section.
^The Backing Plates list as 60-72
^The Shoes list as`71 K/20 only
^The Drums list as`71 K/20 only
^The Springs & Levers interchange through various years.
I don`t want to confuse things any more.But,I`m thinking you just need matching drums/shoes from an HO52.

[1969 GMC]

Originally Posted by Scott McLean

Alright I give in. Too many variables to get it right! So if I am going to put in a 14 bolt, are there some that would be easier to work with than others. I would like to limit the amount of alterations if at all possible. ie ( moving spring perches, shock mounts, shortening drive lines and emergency brake adjustments.
Thank's everyone for your help.

The 14 bolt is doable. You will need one from a one ton, and won't have to move spring perches. Ujoint may be different, too, so you will need to either change the yoke or find a conversion ujoint that is $$.

However, I still say go discs with modified 14 bolt brackets.

[earl87gta]

here is what I have went too if you read the last 3 posts that was me looking to solve my eaton break trouble. Im using a set of calipers off a d44 that I already had so I wont have that much in to the hole convertion maby $150. I may have spent the same or a little less for a 14bff but then I wouldnt have the cool disk breaks. As soon at I get a chance to put them on Ill post pics of the install. http://www.pirate4x4.com/forum/showthread.php?t=477819