Difference in front drums from 68 to 69?

[60ShortStepGMC]

Can anybody confirm that 68 front drums had the "anti-vibration spring" while the 69 front drums did not?

For that matter, can anyone tell me if there's a significant difference between the hubs and drums for these years?

A while back I purchased some 69s (per seller) with the "a-v" spring. Recently someone indicated that only 68s came with the spring. Just trying to learn what's correct, and then if it really even matters (because, basically, they may be interchangeable?).

[CST10]

My 1970 and 1968 both have them all away around the hubs. I don't know if they are suppose to have them or not but they both do.

[CST10]

I think any replacement drums you buy at the store may not have them at all, but don't have any data to verify that.

[71 super]

Spring was used through 70 to my knowledge, all my early trucks had or have them

[michael bustamante]

The drums are the same thru 70. I dont think everyone reused the av springs. I have a 67 and my av rings are missing. I dont notice any vibrating though at all

[Mike C]

My '69 had the springs on the drums all the way around.

[60ShortStepGMC]

Cool, thanks for the feedback. Y'all said pretty much what I thought - there's no real evidence either way.

So the seller said they were 69s, they must be 69s.

[Mike C]

It seems pretty clear to me that they ALL had the anti-vibration spring through 70. And that was confirmed by everybody who posted...

[60ShortStepGMC]

Not everyone had 'em:

Originally Posted by michael bustamante

I have a 67 and my av rings are missing.

All I was saying was that the presence or absence of the "av" spring was no indication of year.

[Mike C]

Ahh. That makes more sense!

[Lattimer]

My 70 had the springs on the front when I got it, but none on the back. I put replacement drums on it and they didn't come with the springs.

[barmanvarn]

I took a wheel off the other day in order to begin figuring out why the brakes on working at all on the old truck. Saw these springs wrapped around the drums and had no idea what they were.

Should I leave them on when I'm done working the brakes? Or can they be discarded?

[VWNate1]

Leave them in place as they not only held prevent chattering / squeaking of the brake shoes , they also help dissipate heat , this is *very* important indeed .

They were gone missing off my '69 so I had to go find them in the junk yard , once again they asked me " why the hell does ONLY YOU buy this weird stuff ?! "

Because of course , I DRIVE and WORK my Light Duty CHEVROLET TRUCK and I accept no compromises ~ if I did I'd prolly have a Brand 'F' truck ~ GAH .

[barmanvarn]

Originally Posted by VWNate1

Leave them in place as they not only held prevent chattering / squeaking of the brake shoes , they also help dissipate heat , this is *very* important indeed .

They were gone missing off my '69 so I had to go find them in the junk yard , once again they asked me " why the hell does ONLY YOU buy this weird stuff ?! "

Because of course , I DRIVE and WORK my Light Duty CHEVROLET TRUCK and I accept no compromises ~ if I did I'd prolly have a Brand 'F' truck ~ GAH .

Thanks for the info. Are they basically a part of the drum? Meaning, they just come off w/ the drum...no special handling needed?

[VWNate1]

Correct ;

They just sit there in a casted in groove .

DON'T take them off because once in a while they're bugger all to get back into place .

OBTW : you should not ' turn ' or ' machine ' the brake drums unless they're severely bell mouthed or so badly warped the brake pedal pulsates under your foot .

This is directly from my BENDIX (the good Folks who engineered the drum bakes on your old Chevy Truck) Factory training ! turning and machining brake drums reduces their ability to dissipate heat , always a very bad thing on drum brakes indeed .

Dealers & Shops like to insist upon it because it's easy money and sells lots of new drums .

Once in a while the Customer runs the brake shoes metal to metal , then what ? .

Simple : take some 600 grit sand paper and smooth up the sharp ridges then re assemble with your new shoes and do a gentle break in by making numerous slow (- 35 MPH) stops , in a few blocks the shoes will be fully bedded in , if you have the original automatic brake adjusters , just back up and make _complete_ quick stops a few times and they're done .

Other wise manually adjust the brakes until there's nu ' SH , SH ' sound coming from the shoes against the drums ~ this tiny bit of clearance is critical to prevent heat buildup as you drive .

Most ' mechanics ' (feh) adjust brake shoes to a light drag , this is wrong and dangerous to boot .

I hope this is helpful .

[barmanvarn]

Very helpful, thanks!

I haven't had a chance to dive into the breaks yet so all I know right now is when we pulled it across the yard (slowly) to get it next to the shop, we found it we had zero breaking. Pedal goes go the floor.

Checked the reservoir and confirmed there is fluid but that's all I can tell you at this point. Have been focusing on getting the engine to run up to this point.

I'll be pulling off drums and checking lines hopefully this weekend.

[VWNate1]

Be smart and replace all four wheel cylinders , three flex hoses and prolly the master cylinder too ~ your LIFE depends on good brakes .

When you're cleaning the various hydraulic parts , only THREE things may be used ~ alcohol , brake cleaner or brake fluid .

NOTHING ELSE as any other chemicals will attack the rubber seals , you cannot clean them after they've been washed in gasoline , wd-40 etc.

Have fun and remember : only take ONE SIDE apart at a time ! you're going to have it apart a while waiting parts and leaving the opposite side assembled , allows you to look at it and figure out where all those little parts go .

[barmanvarn]

Originally Posted by VWNate1

Be smart and replace all four wheel cylinders , three flex hoses and prolly the master cylinder too ~ your LIFE depends on good brakes .

When you're cleaning the various hydraulic parts , only THREE things may be used ~ alcohol , brake cleaner or brake fluid .

NOTHING ELSE as any other chemicals will attack the rubber seals , you cannot clean them after they've been washed in gasoline , wd-40 etc.

Have fun and remember : only take ONE SIDE apart at a time ! you're going to have it apart a while waiting parts and leaving the opposite side assembled , allows you to look at it and figure out where all those little parts go .

I agree with everything you said.

Eventually all of the braking system will be restored and fully functional. For now I'm just shooting to get some semblance of braking so I can move it in and out of the shop under it's own power. That way I'm not stuck working on it in the yard. LOL

Of course I want it safe and roadworthy at some point, but I know that that is a LONG ways away. I'll be happy if I can just drive it across the yard (and stop) at 5 MPH.