65 GMC Front Hub Riveted to Brake Drum

[millspec]

Just like I wrote, I have a 1965 half-ton 2wd with single master cylinder pump and pray manual brakes. I was rather surprised to figure out why I couldn’t remove the brake drums on the front brakes.
At first I thought they were just stuck, so I tried backing off the adjusters. No luck. So, I decided to try removing the hub with the drum by removing the dust cap, cotter pin and nut. It came off and to my surprise, the hub is riveted to the brake drum in 3 places!
Of course, the drum is worn, so I need to replace it.
I have looked in the factory service manual, but haven’t been able to answer the questions why and can I drill out the rivets and use a regular brake drum?
The NAPA 440-1071 brake drums seem to have the extra holes for the rivets, but must they be used?https://uploads.tapatalk-cdn.com/20260225/d211b83919ec0f545c6915b70856426c.jpg


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[lizziemeister'sV6]

You don't need to rivet the front drums to your hubs. Your back drums are loose. What you do need to do is to get the proper drums for your GMC - Chevy drums are not the same as GMC. Lots of parts stores will tell you they are the same - they are not. GMC's have an offset near the lug bolt holes. Take your old drums to compare when you get new. Hopefully other GMC owners will agree with what I said. Any comments?

[millspec]

I’m not sure what you mean by offset. I compared the drum from NAPA to the current one. The hole in the center for the hub is larger on the NAPA version in order for rear axle fitment. When I place it on top of the front hub upside down, there’s about 0.125” clearance around it.
The picture shows some tabs that are bent in which the NAPA part doesn’t have. I’m not really worried about those, but is it okay for the hub hole to be larger than the hub center?
If you happen to know the correct drum part number and a source, I would greatly appreciate it.


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[millspec]

11433


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[Prowbar]

Hmm. On my 1500 they are not riveted on, just held on by the lug nuts. But the center bore is a proper fit.
I'd say that the center bore needs to be the right size.
Can't imagine why GMC would use a different drum than Chevy.

What is the diameter of your hub?

I'm looking at Rockauto for a 1965 1000 series, the drums I've looked at list a 90.5mm (3.57") center bore.



Let us know what you find.

[millspec]

You don't need to rivet the front drums to your hubs. Your back drums are loose. What you do need to do is to get the proper drums for your GMC - Chevy drums are not the same as GMC. Lots of parts stores will tell you they are the same - they are not. GMC's have an offset near the lug bolt holes. Take your old drums to compare when you get new. Hopefully other GMC owners will agree with what I said. Any comments?


I took a closer look and some measurements today…and I stand corrected. The center bore size is the same both front and rear at about 0.357”. Also lizziemeister’sV6 was correct about the flange being deeper. When I put the NAPA part on the rear, the drum was not deep enough to completely cover the shoes when fully seated. I would estimate the NAPA drum lacks about 0.250” or so.
They are not the same. I will look at the rock auto drums, but not sure they won’t be the same as the NAPA.
Thanks for the help.
I’ll keep you posted as to what I eventually figure out, but if anyone has any additional suggestions or information, I’m all ears.


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[Prowbar]

Ahh. Now I understand what you mean by offset. Nice job Lizziemeister!

Can you have these drums turned or is there no material left?

[millspec]

Prowbar,
I haven’t checked into machining the drums, but I hesitate to do so for a couple of reasons. First, since the hubs are riveted to the front drums, I’m not sure they can be machined without removing the rivets. This what drove my original post. Second, when I was a kid I used to work in an auto parts store. They used to turn brake drums and also used a machine to re-arc new brake shoes to match the newly machined brake drums.
If I can’t manage to find new drums, I may have to explore machining the old ones.


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[Prowbar]

I understand. Rivets can be drilled out and new rivets can be put in. They need to be removed when you install a new drum anyway.

If you have a shop that turns rotors, it would be worth asking of they can machine it with the hub still on. Maybe a good machine job wants to try it. If you put some nuts and spacers on the lug studs you should be able to reduce most of the chatter I think. Then it can be machined in as one assembly.

Remove the grease seal and wheel bearings and use a live center in the lathe to machine it.

Let us know how it goes.

[millspec]

Thank you. I suppose the actual first step is to get the drums measured to see if they are currently within spec and have enough material to be turned. I have to get a service manual to look the spec up as there’s no writing on the drums that I can find.
Would anyone happen to know what it would be? I’ll look it up when I get a manual, but would appreciate a cross check.
I admit I’m a bit nervous about having them turned. I messed up more than one drum when I worked at a parts store and (so far) I haven’t had any luck finding replacements.
The brakes didn’t pulsate when I took them apart, so they should be fairly round.
Thanks again for the help.


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[sclor]

Millspec:
Couple of thoughts:
If you have front drums riveted, they are likely original to the truck. Surprised at how long they have lasted. I had to change one of my fronts. I found grinding the head off of the river to be the easiest way to take it apart. I believe the Chevy drums for the front will be the same as your front drums.

Rear drums are a different story. We have Dana 44 rear vs Chevy that use "corporate" rear. Our rear drums do have more offset than Chevy. When I had this problem, I found the front drums for 4 wheel drive Chevy ilate sixties used six lugs and Dana 44 in their fronts. Those drums had fins but were the closest I found for use in our rear. You can use search function and find my posts in the past on this or I can look up the part on Rock Auto if you want me to.

Hope that helps..
Regards
Steve
New Orleans

[sclor]

Millspec:
Looks like rear drums I mentioned are getting harder to find. Part I used was raybestos 2067r. Rock only lists one in stock. I found some more at website below.

Hope this helps.
Regards
Steve
New Orleans

[sclor]

Millspec:
One other thing I forgot to mention is that I had to drill holes for lugs from 1/2" to 9/16" on these drums to fit the collar that we have on our studs.
Regards
Steve
New Orleans

[Prowbar]

My 1965 manual doesn’t listed a maximum spec other than to not machine drum larger than .060 over nominal size. Now Rockauto does list a discard spec for the Chevy drum at 11.06 inches. Assuming std. size is 11 inches. Makes sense with 11x2 brake drums.

[millspec]

Prowbar,
I took your advice and took the drums to a local machine shop. They are all worn well past 11.06”. Three were worn past 11.085” and one was over 11.09”.
Steve,
Thank you for the information! I will look into those Dana 44 drums for the rear. Was there any problem with wheel figment due to the fins?
As for the fronts, I will have to look closer at the front drums to see if they are the same as a C10.


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[Prowbar]

Well, it was worth a try. Good luck on your quest to find new drums.

[sclor]

Millspec:
Fins on the drums weren't a problem. Only mod necessary was drilling lug holes to 9/16"
Regards
Steve
New Orleans

[millspec]

Steve,
I looked on partzilla but not seeing the Raybestos R-Line 2067R. I see one on Rockauto but need 2.
Do you have a link for the partzilla?


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[millspec]

Steve,
I looked on partzilla but not seeing the Raybestos R-Line 2067R. I see one on Rockauto but need 2.
Do you have a link for the partzilla?


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Never mind. I found them. Sorry about that.


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[sclor]

Millspec:

Try this:

https://www.partzilla.com/product/automotive/RAY-2067R?srsltid=AfmBOoqpMllBZLHRgnFZdzW9eZCwlXN0_qvY WbDFqXhMfy9-IJBen-4E

Otherwise search " raybestos 2067r " and that should bring it up as well.

Regards
Steve
New Orleans

[beerman]

I believe the rear drums are specific to the Dana 44, at least they are on my 68. Not sure about the 2067r's but usually the cross-referenced replacements are close but do not cover the entire shoe. Centric used to make a replacement for the GMCs but that was 10 years ago. Guys over on 67-72 Chevy truck forum have successfully modified Jeep drums to fit the Dana 44's unique offset.

[millspec]

I have ordered the 2067r’s and will let everyone know what I figure out. I’m hoping all that needs to be done is drill the holes for the lugs to 9/16”.


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