Prior to the squarebody, there was more separation between GMC and Chevy as far as the trucks went. The further back you go the more different they were.
Larry's Yellow GMC big block truck originally came with a D60 6 lug axle too.
CK5
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Larry's Yellow GMC big block truck originally came with a D60 6 lug axle too.
Ooo
Was that d60 a 19 spline?
Yes, as far as I remember. Some of the Chevy trucks got them too. I saw a couple of them.
I never have seen a 2wd with 6 lug past '71 though. Well until the GMT400 did the light duty 2500.
Don't know. I do know he broke it in high school and swapped in a d44 to get by. The 44 is still in there.
In 1/2 ton applications:
Chevy and GMC were both 6 lug from 1960-1970. Chevy used a small Eaton until switching to the 12 bolt with coil spring and trailing arms vs GMC with the Dana 44, however 60-62 GMC also used trailing arm and coil springs. Starting in 1967, Chevy offered leaf springs as an option while GMC offered trailing arms as an option. By 1971, Chevy and GMC were both using identical suspension and axles on the identical frame.
Really this all just caught me out making some assumptions that #1) all truck 12 bolts were 6 lug and #2) 2wd 1/2 ton trucks had 10 bolts. I think part of the reason I made this mistake is because the 64 C10 I had in high school was a 12 bolt but it was 6-lug. I guess it makes me wonder why they even went to 5 lug. And it's a hard lesson because I bought a diff cover than doesn't fit my axle. 
For clarification this is my axle:
Which is definitely a 12 bolt cover.
Pull the bearing on the other side and even using the special tool, things can go wrong.
This bearing really didn't want to come out. Luckily I could rotate the puller foot 90 degrees and didn't break any more of the bearing. It took a lot more effort on the slide hammer to this side out compared to the other side.
I was irritated to find the bleeder on the new wheel cylinder was metric, like fricking 10mm, who has metric wrenches.
Anyway I swapped in the old one after cleaning the dirt out of it.
I like that it's longer anyway. Plus I hate having to guess which size wrench the bleeder needs. Better to keep them all 3/8".
When the new drums show up later this week, I should finally be able to finish. Obviously I also haven't been working real hard on it anyway since I'm working from home. But I would like to get the 66 back in the garage.
For clarification this is my axle:
Which is definitely a 12 bolt cover.
Pull the bearing on the other side and even using the special tool, things can go wrong.
This bearing really didn't want to come out. Luckily I could rotate the puller foot 90 degrees and didn't break any more of the bearing. It took a lot more effort on the slide hammer to this side out compared to the other side.
I was irritated to find the bleeder on the new wheel cylinder was metric, like fricking 10mm, who has metric wrenches.
Anyway I swapped in the old one after cleaning the dirt out of it.
I like that it's longer anyway. Plus I hate having to guess which size wrench the bleeder needs. Better to keep them all 3/8".
When the new drums show up later this week, I should finally be able to finish. Obviously I also haven't been working real hard on it anyway since I'm working from home. But I would like to get the 66 back in the garage.
I did the same with the buick bleaders on the new cylinders. Really bugs me that they do that.
What I don't get is the threads are still the same which I'm guessing is an SAE thread.
I have not ever checked to see what those threads are.
So much for best laid plans. I replace the wheel cylinder on the other side and it has been replaced in the past. The bleeder on it uses a 5/16" wrench and it will not thread into the new wheel cylinder because the threaded side is also smaller.
To further confirm the wheel cylinder had been replaced, and by a hack, you can see the flare nut has been chewed up along with one of the mounting bolts.
Some a-hole using vice grips I'm sure.
For what it's worth, the smaller bleeder:
In the end, despite my best efforts, I still ended up with metric bleeders.
I couldn't help but add a bling-bling cover. Even tho I'm probably the only one that'll ever see it, it's like my reward for the hard work.
I know it's on there. 
To further confirm the wheel cylinder had been replaced, and by a hack, you can see the flare nut has been chewed up along with one of the mounting bolts.
Some a-hole using vice grips I'm sure.
For what it's worth, the smaller bleeder:
In the end, despite my best efforts, I still ended up with metric bleeders.
I couldn't help but add a bling-bling cover. Even tho I'm probably the only one that'll ever see it, it's like my reward for the hard work.
I know it's on there.
Of course as soon as I start the truck and depress the brake pedal I'm reminded I still need to replace the vacuum booster as the RPM rise every time I push the brake pedal.
Part of the reason I hadn't replaced it yet is because all I could find was reman'd boosters in which they don't even replace the diaphram. I finally found this one on Summit: https://www.summitracing.com/parts/tff-2232nb The only catch is it specifically says GMC for the application, otherwise it's for the correct year and 2wd 1/2 ton. Anyone know of a reason it wouldn't work in a Chevy?
Part of the reason I hadn't replaced it yet is because all I could find was reman'd boosters in which they don't even replace the diaphram. I finally found this one on Summit: https://www.summitracing.com/parts/tff-2232nb The only catch is it specifically says GMC for the application, otherwise it's for the correct year and 2wd 1/2 ton. Anyone know of a reason it wouldn't work in a Chevy?
The description says Chevy and GMC.
Interesting, I see that now. Must just be a glitch on Summit's part that they only list GMC for application. I didn't know they actually made a C15.
Interesting. It was still on the choke so idle was high. What is it the torque converter is doing?
I like automatics, but all the internal stuff is like magic to me. In the navy nuke program when the instructors didn't want to explain the details of how something worked and we didn't need to know, they would tell us it's PFM = Pure ****ing Magic. That's how I feel about automatic transmissions.
C15 was the GMC equivalent to Chevy C10.
