C1 62 brake drum part number?

[Chris H.]

What was the brake drum part number used on base 62's?

3 of mine have part number 3752623 stamped in them and fit fine. My 4rth has a different number and has been hammered on and off because it is too tight on the center.

Was this drum used on 63's?

thanks, Chris

[Mike M.]

Re: C1 62 brake drum part number?

63 drum won't interchage with a 62 drum. mike

[Duke W.]

Re: C1 62 brake drum part number?

The number you report is a drum CASTING NUMBER, not a finish machined drum part number that is called out in the parts catalog, and this casting was used to manufacture at least two finished drum part numbers - one for base brakes and one for RPO 686 (J-65 in '63 and '64) metallic brakes. Drums machined for 686/J-65 applications have a finer finish on the friction surface, which is the only difference.

The 2" 3752623 drum would be applicable for both ends of C1, but was only used on the rear of C2s since C2s got wider 2.5" front brakes. One of the original drums on my J-65 '63 is a 3752623 casting. The other is 3828688.

Can you find a casting number or any other identifying marks on the fourth drum?

Duke

[Duke W.]

Re: C1 62 brake drum part number?

Mike - My Chevrolet parts catalog shows the same (2") drum part number (base brakes) for all 53-62 front and rear and 63-65 rear.

The '63-'65 drum brake cars have a different front drum part number because the front drums are 2.5" rather than 2".

Duke

[Chris H.]

Re: C1 62 brake drum part number?

thanks, I looked at my photos and it is 3828688.

[Duke W.]

Re: C1 62 brake drum part number?

Interesting that both our cars have both 688 and 623 2" drum castings. I can't recall if I noticed any meaningful difference in their geometry, but they were apparently both in production at the same time and were used interchangeably to machine finished drums.

Corrosion at the hub/drum interface can cause the drum to stick. Usually a good wire brushing or sanding of the mating surface will free them up and allow them to be easily slipped on and off as long as the shoes aren't adjusted too tight, especially on a drum that has wear. The shoe edges can hang up on the wear lip.

Duke

[Chris H.]

Re: C1 62 brake drum part number?

Duke, my single drum has been beat off many times. The center web has hammer marks and I have pryed and hammered to get it off also. The center diameter is just to small. Next time I have it off I will do some sanding to make it fit better.

I wonder also if both part number castings were used that year in production?

I do have a 3868801 drawing Drum Assembly-Rear Brake. I must have it because some '62 drawing referred to it. There are revisions thru 3/3/71 but what is strange is that there is a drawing date of 6-2-64 but it was redrawn 1-28-63 which means it must be older. It has references to part numbers 3985945, 3828670 and 3869538. Any idea what this drawing was for?

Chris

[Chris H.]

Re: C1 62 brake drum part number?-photos

Duke, I have photos on the below website of both drums. The most noticable difference I recall is that the 3828688 has an oblong slot on the outside. 3762623 does not. Use chenige for both user and password.

My drawing that I referred to has this slot but does not show any dimensions or notes on its possible usage.

http://www.photodex.com/sharing/viewalbum.html?alb=83126

[Duke W.]

Re: C1 62 brake drum part number?

It sounds like you have a copy of drawing number 3868801, so I don't know why you are asking me what it might be. What does it show?

I can tell you that 3985945 and 3869538 are later 2" drum CASTING numbers. Got one of each when I bought new rear drums for my J-65 brakes. According to my notes the 945 drum has the "max dia. 11,090" molded into the casting. The 538 drum has no evidence of the max diameter statement either stamped or molded.

3828671 is the casting number for my original 2.5" front drums, so I would be willing to bet that 3828670 is a machined version of the 671 casting. The replacement front drums I bought are casting numbers are 3869532, so this part was going through the system at the same time as the 538 rear casting since they are separated by only six.

One thing that I have never figured out is if the service drums were supposed to include and anti-squeak spring or not. If so then the drum/spring "assembly" would have had a different number than the finished drum.

I calipered the 538 and 945 hub holes and they are both in the range of 2.810-2.815 inches.

Duke

Duke

[Duke W.]

Re: C1 62 brake drum part number?-photos

Yes upon reinspection my 688 casting has the "knockout" but the much earlier 623 casting does not.

You'll have to refresh my memory on manually adjusting drum brakes, as I have not done a brake adjustment since I was a teenager in the sixties, but I recall that the star wheel access is on the backing plate and I spun the wheel while moving the star adjuster until I got just a bit of drag.

My '63 has self adjusting brakes, and I don't think there is a hole in the backing plate to access the star wheel. A drum can be tough to pull off if the brakes are adjusted snug, so my theory is that the later 688 casting got the "knockout" so it could be punched out to reach the star wheel if the drum wouldn't slip off.

Duke

[Robert Jorjorian]

Re: C1 62 brake drum part number?-photos

Chris
I believe production brake drums prior to 1963 did not have a knock-out in the drum but had a adjusting hole in the back plate. Beginning in 1963 the adjustment changed to the drum side and the drum has knock-out.
This would mean an early drum without a knock-out incorrect for 63 and later,and drums with knock-outs incorrect for pre 63.
Also 1963-64 front brake shoes are 2 3/4 inches wide not 2 1/2.
Rear 63-64 shoes are 2 inches wide.
Regards, Robert

[Chris H.]

Re: C1 62 brake drum part number?

This drawing has no vehicle usage. Just says Drum Assembly-Rear Brake.

The casting detail you refer to was revised from ??? to 3828670 on 8-3-67. It was again revised to 3828670 on 12-3-69
and again revised to 3985945 3-3-71

As a point of dating, there was a slot added to the center section 8-3-67. It was just outside the 4.75" diameter. The hole it replaced was reinstated 11-15-67 and the slot remained optional. Therefore if there is this slot (not the adjusting slot) the drum was made after 8-3-67. (IF any parts were made with the slot)

The drawing shows 5 holes for the lugs and a 6th just outside the 4.75" lug diameter(referred to above). My drum of the same part number has 3 round holes with one having a tang in it. Therefore it was made before the drawing was redrawn before 1-28-63.

None of this answers the question if 3868801 was a production part for a '62.

Chris

[Duke W.]

Re: C1 62 brake drum part number?

What size drawing is it? Can you photograph and make a legible file that you can place on your photo site?

Duke

[Michael H.]

Re: C1 62 brake drum part number?

Chris,

I'm not sure exactly when the 3868801 entered production but I know for sure that it was never used on any 62. That number, numerically, wasn't even in the system at that time. It's first arrival would probably have been in early or mid 65. GM part numbers increased in numeric value as time went by (with a few exceptions) and for 62, the range would have been roughly 379xxxx. The 3828670 would have been slightly after introduction of the 63 model year. I know the 3828xxx part number was replaced with a 3869537 some time in early or mid 65 and that would probably have had a casting number somewhere near that. I don't remember what the physical change was from the original 63 number but I know the 65 number serviced all 63-65's from that point.

I can dig out some of this info if needed.

[Chris H.]

Re: C1 62 brake drum part number?

Michael, the drawing is dated 6-2-64 BUT it was redrawn on 1-29-63 which does not make sense. Someone messed up and changed the drawing date. The drawing part number was out before 1-29-63. Of course after the drawing is done there is time to tool it up but again my part on my car (which probably not on my car at production) precedes the 1-29-63 redrawn date specifications.