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1966 Chevelle SS396
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My friend is looking for a stock '70 Chevelle spindle w/disc brakes. The GM P/N is 3966151; he would prefer a nice used GM piece to an aftermarket one.

I'd like to find out what applications use the same spindle, so we know what other cars to look for. So far, I have these:

1967-69 Camaro; 1967-72 Chevelle/Buick Skylark/Olds Cutlass; 1968-74 Nova; 1970-72 Monte Carlo; 1970-72 El Camino/Sprint; 1971-74 Pontiac Ventura; 1973-74 Buick Apollo/Oldsmobile Omega

Am I correct so far? Anything to add?

Thanks a lot! :thumbsup:
 

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66 El Camino 57 Chevy pickup 2004 Tahoe
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That's about it. See your PM from me
 

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if he has drum spindles, then tell him to break out a cutoff wheel and make them into disc spindles.. the only difference is the height of the upper boss.
 

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It's a disc brake car; he wants to find one correct disc spindle for it.

Thanks! :)

a drum brake spindle was made from the same forging as the disc spindle- they just machined the upper boss down lower for the disc brake bracket. just bolt the bracket to the lower bolt and pivot it up against the upper boss.. scribe a mark where it will bolt down flush, and cut it to that mark. it doesn't need to be very precise- as long as the upper bolt clears the back of the rotor, the floating caliper will compensate.
 

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Re: 72 El Camino drum spindle conversion for stock disks??

if he has drum spindles, then tell him to break out a cutoff wheel and make them into disc spindles.. the only difference is the height of the upper boss.
Where can I find some additional information or photos on this mod?? I have a '72 el Camino (drum brakes), and also have the disk brakes from a '69 Camaro and would like to use them on the El Camino. I would prefer doing this mod to changing the spindles...
 

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Re: 72 El Camino drum spindle conversion for stock disks??

Where can I find some additional information or photos on this mod?? I have a '72 el Camino (drum brakes), and also have the disk brakes from a '69 Camaro and would like to use them on the El Camino. I would prefer doing this mod to changing the spindles...
This is what you aim for:


and according to this, you need to remove 0.610" to achieve it.

 

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Thanks Denny. Seems the only problem is to remove the spindles and take them to a decent machine shop for the machining.

Removal of the spindle without destroying the ball joint grease seals: The associated reference read... "There are some cases when you need to separate the ball joint from the spindle and don't want to potentially damage the ball joint and its boot by using a fork-type separator. David Pozzi was nice enough to make me one of these awesome ball joint presses from some simple ½-inch hardware and some steel. He machined a small recess in the ends to keep them centered on the ball joint studs during removal. Simply loosen the ball joint nut a couple of threads and expand the press to break the ball joint loose." with the associated photo of the 'tool', but it was not clear to me how this tool worked? Can anyone assist?
 

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you can modify the spindles without taking them off the car.. takes like 30 seconds with a cutoff wheel..

and a nice manly hammer blow to the spindle next to the balljoints with a nice manly hammer pops them right out if you do want to take them out for some reason..
 

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I modified some drum spindles for disc brakes. Besides trimming off the upper boss I also had to buy a tap and tap the threads deeper in that boss for the bolt to go in far enough.
 

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you can modify the spindles without taking them off the car.. takes like 30 seconds with a cutoff wheel..

and a nice manly hammer blow to the spindle next to the balljoints with a nice manly hammer pops them right out if you do want to take them out for some reason..
If that machine surface doesn't need to be 'precise', is the dust shield the only thing that mounts to it?

I've always used the 'manly hammer' blow method, but I couldn't figure out how that tool that was shown would work... Has anyone used one that can explain the process?

Another question: If I install the '69 Camaro disk brake rotor and caliper, is there any need to replace the drum brake MC and booster? I think the drum brake unit is a 1" MC, whereas the disk brake MC is a 1-1/8" ? Any difference in the booster?
 

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If that machine surface doesn't need to be 'precise', is the dust shield the only thing that mounts to it?
It holds the caliper bracket as well.

I've always used the 'manly hammer' blow method, but I couldn't figure out how that tool that was shown would work... Has anyone used one that can explain the process?
You put the tool between the 2 ball joint studs and unscrew it such that it get longer and pushes the studs out.

Another question: If I install the '69 Camaro disk brake rotor and caliper, is there any need to replace the drum brake MC and booster? I think the drum brake unit is a 1" MC, whereas the disk brake MC is a 1-1/8" ? Any difference in the booster?
You need to replace the m/c (read post #2 of this thread for suggestions).

All boosters from any GM car model or year (60's - 80's) are interchangeable (Although they don't necessarily perform the same, i.e. an 11" gives more assist than a 9", but also takes more space).
 

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All boosters from any GM car model or year (60's - 80's) are interchangeable (Although they don't necessarily perform the same, i.e. an 11" gives more assist than a 9", but also takes more space).
Let's be careful about the booster-to-master cylinder pushrod length.

Some masters use a long pushrod, some use a short pushrod. Most pushrods aren't adjustable, and the ones that are won't adjust from "long" to "short".

There was a time I thought the short pushrod/shallow pushrod seat in the master cylinder vs. long pushrod/deep pushrod seat had to do with Delco vs. Bendix master cylinder/booster pairings. I'm not convinced any more that's exactly how it works.
 

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Let's be careful about the booster-to-master cylinder pushrod length.

Some masters use a long pushrod, some use a short pushrod. Most pushrods aren't adjustable, and the ones that are won't adjust from "long" to "short".

There was a time I thought the short pushrod/shallow pushrod seat in the master cylinder vs. long pushrod/deep pushrod seat had to do with Delco vs. Bendix master cylinder/booster pairings. I'm not convinced any more that's exactly how it works.
All GM boosters have the same bolt pattern to the firewall as well as to the m/c. The only difference can only be the push rod length.

With Delco-Moraine boosters (by far the most popular models), you can easily swap the 2 push rod models that exist. With Bendix, you are stuck with a long push rod.

From what I know, you are right and push rod length was a Delco-Moraine (short) vs. Bendix (long) thing.

In my '69 Pontiac Service Manual (which covers all Pontiac: full-size, Grand Prix, Tempest, Firebird), the brake chapter is divided into 6 sections:

  • standard brakes (manual pedal, drums, hydraulic system, parking brake)
  • disc brakes (which covers only disc, caliper and metering valve)
  • Delco-Moraine power brakes
  • Delco-Moraine heavy-duty power brakes (tandem diaphragm)
  • Bendix power brakes
  • Bendix heavy-duty power brakes (tandem diaphragm)
The 4 last sections have no mention of model specifications. There is a «push rod adjustment» sub-section in all 4 sections.

Both Delco-Moraine models use the same J22647 gauge for the push rod adjustment (conclusion: all Delco-Moraine have a short push rod).

dm.jpg

For Bendix models, they are 2 different gauges (J7723-01 & J22644), but the specs are given to build one yourself or measure it directly:

  • single diaphragm: 1.225" (min. 1.210")
  • tandem diaphragm: 1.200" (min. 1.185")
Which are clearly 2 versions of the «long» push rod.

bendix.jpg

What? 2 versions of the «long» push rod? Do we have 2 versions of m/c also? Apparently there was. In the «standard brakes» section - where the hydraulic system is explained - there is a «master cylinder usage chart» which is separated into 2 sections - you guessed it - Delco-Moraine and Bendix. Note how there is a m/c for «Bendix power drum» and another one for «Bendix power drum (heavy duty)»:

chart.jpg

Note also that it seems that only the full-size Pontiac models could have the Bendix boosters.

So the long Delco-Moraine push rod came later. But I don't know if it is GM or some aftermarket company that created it. I suspect GM abandon Bendix boosters at some point but they still needed a Delco-Moraine long-push-rod booster version for replacement part.

In case - after reading the previous - someone asks the question: How do you adjust a non-adjustable Delco-Moraine push rod? If the push rod was out of specs, you had to replace it with a «service adjustable push rod and adjusting screw in end to match height of gauge.»

Yep, there are also «short» adjustable push rods out there.
 

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Thanks for that.
 
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