70 5 lug disc brake thread

[PT'S 70 CST]

This is a new thread carried over from the one I had posted on the parts board for some 70,71 and 72 wheel studs. The parts book that I got this info from came from a buddy of mine that is a GM parts manager for 30+ years and he said in the book this part #3985844 clearly states that these studs are for 70 disc and 71,72 all. I have a 70 5 lug disc truck and have seen a few others and have been convinced that some of the late run 70 1/2 ton models that were highly optioned were offered with 5 lug disc. Here is some of the documentation that I have and will try and post pics of the info out of his parts book as soon as I get it. Here are four pages of options sheets from the GM dealership. I know there are a ton of yall who disagree about this but all I ask is to keep this thread clean.


Thanks PT

[Vintage Windmills]

Neat topic! Would there be a date code on your calipers or mounting plates? I don't know if these parts were date marked but that could be helpful if so. I need to go out and look at my 70 CST parts truck now

[special-K]

I read through your parts thread with all the responses as to whether 5-lug discs existed. I have never seen a '70 C/10 with 5-lug discs either. But,that's the only proof anyone has provided so far. I've been into these trucks since day-1 and always knew what I knew from what I saw,which was a heck of a lot. I have learned I was wrong about many things by being on this site with all it's members from such a widespread area. I have dealer data books that state tow hooks weren't available on Blazers with chrome bumpers. They also say that all two-tones had white accent except the Dark Olive/Medium Olive and Medium Olive/Grapefruit combos. I have seen proof here that GM info is not true. I have seen a '70 Sierra Grande with Chevelle Black Cherry paint on the SPID. So,I can't honestly 100% deny what a person claims based on what I've seen.
I have the 46-72 Chevrolet Truck parts book and under PN 39858844 is shows 10 required,rear,and for 70 C-1 w/disc brake,71 G-20,71 Ser.10 (exc. 4/WD). It does not give a size. PN 1235137 calls for 10,is for 72 Ser.10 (exc. 4/WD),72 G-20,rear,and is 1/2"-20 x1 3/4". Under front hub it lists 63-70 Ser. 10,G-10-20 (exc. 4/WD),70 (Conv.) (Blazer),71 G-10,20.....3980406 A.R. (7/16"-20 x 1 3/4") and 71-72 Ser-10 w/disc brks. (exc.4/WD),71 G-20 w/disc brks.....3961258,calls for 10 (1/2"-20 x 1 7/8").
We know the '70 rear was the same as 71/72 so that explains why the studs would be the same. I think what causes the confusion is the book lists 70 C-1 w/disc brake clearly on it's own line and separated with a comma from 71 G-20. It sure looks like '70 C10s were available with disc brakes by that. But,on the other hand,there is no listing for a disc brake front stud for '70. Do 71s and 72s have different size studs? I never knew that.

[too much stuff]

Here is some info i found.
Pic one is from a 70 book and pic 2 and 3 are from a brochure.

[OhOneWS6]

How about a picture of your 70 front control arms. I am curious if the shaft bushing are screw in or press in. Press in bushings would confirm that at some point someone converted that truck with 73 up front suspension parts. Screw in would not confirm factory front disk on 70 as it still could have been converted with 71-72 parts. It just might be one more piece of the puzzle.

[PT'S 70 CST]

Thanks for all of your input. I will try asap to look for all of the info some of you have asked for but it will probably be Tuesday or so because I am on 12 hr. nights until Tuesday morning. As soon as I can get the time to get out there and jack up the truck and look for all of the info that you have provided I will gladly do so.


Thanks PT

[mcbassin]

PT,
I can only assume your 70 has 5 stud 12 bolt rear diff too? It will definetly have some numbers stamped on it.

[OhOneWS6]

Originally Posted by mcbassin

PT,
I can only assume your 70 has 5 stud 12 bolt rear diff too? It will definetly have some numbers stamped on it.

Even that will not be definitive. 71-72 axles could have been put in the 70 housing.

[mcbassin]

Originally Posted by OhOneWS6

Even that will not be definitive. 71-72 axles could have been put in the 70 housing.

I know it won't be a 100% confirmation but it will get you one step closer to figuring out this mystery. I was actually thinking of someone changing the whole differential.

[OhOneWS6]

Originally Posted by mcbassin

I know it won't be a 100% confirmation but it will get you one step closer to figuring out this mystery. I was actually thinking of someone changing the whole differential.

True. If the housing is a 71-72 that would confirm a conversion.

[special-K]

We know '71 was the first year front discs were "standard",which meant "all" trucks came with them. We know that drum brakes were "standard" on "all" trucks from '70-back. The question is whether it's possible discs were "available" in '70 on C/10s at any point.

[OhOneWS6]

Originally Posted by special-K

We know '71 was the first year front discs were "standard",which meant "all" trucks came with them. We know that drum brakes were "standard" on "all" trucks from '70-back. The question is whether it's possible discs were "available" in '70 on C/10s at any point.

Agreed. What is interesting about this are the two comments by PT in his original tread.

Originally Posted by PT'S 70 CST

Some of your 70's were 5 lug disc especially some of your more highly optioned trucks. I have a 1970 CST three owner truck and it is an original 5 lug disc brake truck.


PT

Originally Posted by PT'S 70 CST

I will see if I can get you guys some black and white info on this. I have seen several 70's with disc in this area. The info on these studs was given to me by one of my good friends that has been a GM parts manager for 30+ years and I would damn near trust anything he told me about a GM product. The info he gave me came straight out of a GM parts book.


PT

If they were even somewhat common you would think some of you old timers would have seen it before. I find it had to believe, even if it was an option, that disk on a 70 would be that rare. PT is the only person I have ever heard say he has seen one and beyond that he has seen more than one.

[special-K]

Originally Posted by OhOneWS6

Agreed. What is interesting about this are the two comments by PT in his original tread.






If they were even somewhat common you would think some of you old timers would have seen it before. I find it had to believe, even if it was an option, that disk on a 70 would be that rare. PT is the only person I have ever heard say he has seen one and beyond that he has seen more than one.

I don't see anyone saying it was somewhat common,except you. I can see where if he believed his truck had factory disc brakes,then he might have assumed others he saw were. I showed where anyone just looking at that part number could surmise that a '70 C/10 was available with 5-lug disc brakes. I've also showed where GM documentation doesn't always hold true to fact. Based on what I know,I don't think '70s were available with disc brakes. But,I am open to learning something I didn't know sooner than be suspect. I've learned a lot from this site despite all I knew when I first came here and I'm still learning. If he's wrong,he's wrong and I'm sure he will admit it once we let this run it's course. Not many people have actually responded as yet. And,only one "old-timer"...ERIC!

[too much stuff]

Originally Posted by special-K

I don't see anyone saying it was somewhat common,except you. I can see where if he believed his truck had factory disc brakes,then he might have assumed others he saw were. I showed where anyone just looking at that part number could surmise that a '70 C/10 was available with 5-lug disc brakes. I've also showed where GM documentation doesn't always hold true to fact. Based on what I know,I don't think '70s were available with disc brakes. But,I am open to learning something I didn't know sooner than be suspect. I've learned a lot from this site despite all I knew when I first came here and I'm still learning. If he's wrong,he's wrong and I'm sure he will admit it once we let this run it's course. Not many people have actually responded as yet. And,only one "old-timer"...ERIC!

Not sure if i am the old timer you are looking for...
I posted some pics above that would show no discs in 70 for the 10-30 series and showing them as new for the 71 models. I have looked at ALOT of lit. today and can't find anything showing discs as an option for 70. Not in sales brochures, parts books, or accessory brochures. I couldn't even find that part number in the 70 book. I did find it in the 72 gmc parts book and it lists it as a rear hub for an ho 35, spicer 44 and 60-35, ho 52, ho 72, sp 60 and h110. These are all for a rear hub.
Now, that doesn't mean alot, just means i didn't find anything. My personal opinion, discs didn't come out until 71 on 10-30 series.

Lolife99, that axle would have continued for along time afterwards on the 4x4

[OhOneWS6]

Originally Posted by special-K

I don't see anyone saying it was somewhat common,except you. I can see where if he believed his truck had factory disc brakes,then he might have assumed others he saw were. I showed where anyone just looking at that part number could surmise that a '70 C/10 was available with 5-lug disc brakes. I've also showed where GM documentation doesn't always hold true to fact. Based on what I know,I don't think '70s were available with disc brakes. But,I am open to learning something I didn't know sooner than be suspect. I've learned a lot from this site despite all I knew when I first came here and I'm still learning. If he's wrong,he's wrong and I'm sure he will admit it once we let this run it's course. Not many people have actually responded as yet. And,only one "old-timer"...ERIC!

I'm not getting in a pissing match with you. I never said it was somewhat common. I was referring to PT's comments from his other thread hence the bold type in the quote above my comment. You really have to walk on egg shells around this place. Oh well. It is what it is. I'll be watching but I will not comment again on this thread.

[lolife99]

I believe its possible,... even though I've never seen it.

Has anyone ever explained why GM started using the 71-72 "width" rearend housings in the '70 model year?
(even though they had 6-lug axles)

I don't understand why they would change the 6-lug axle length for just a partial model year.
Did they change suppliers?
Sure the "housings" will be carried over to the next production years (71-72),... but to make a specific 6-lug axle that was longer than the previous 67-69 axles seems odd to me.

Maybe there were a few prototype "executive" built trucks that had a "preview of things to come", on their high optioned personal trucks.
Who knows.
But I'm interested,...

[lolife99]

No need to "walk on eggshells".
We are all here to learn and discuss.

It is so hard to understand what is said in the "typed word", here on the internet.
I'm sure nothing personal was meant.

[special-K]

Originally Posted by lolife99

No need to "walk on eggshells".
We are all here to learn and discuss.

It is so hard to understand what is said in the "typed word", here on the internet.
I'm sure nothing personal was meant.

I agree,no need to walk on eggshells at all. Not sure where that notion even came from. The typed word can be taken wrong easily,but I feel I take a lot of effort to put my words down as clearly as anyone possibly could. I'm saying PT never said disc brakes are "fairly common",plain and simple. As I said before,only one person said that. As I have stated I have read all the posts in both the parts thread and here. I also expressed I am always learning,and that's what's happening here. I am open to whatever the result is. That's how you learn and it's certainly not taking a stance pro or con.
I hope everyone can see there is no temper in my words,just trying to be even more clear. And Eric,that was just me fooling around with you over the old-timer remark since it seems it was referring to "US". I think if it's possible for some '70s to have had 5-lugs w/discs it wasn't an option,but more like an exception to the rule,like a manual shift Highlander or any of the many other things we've seen around here. I had a Grapefruit '72 Blazer that said Wheatland Yellow on the SPID.

[stsalvage]

Now i know for a fact that GM did do a lot of things for movie stars big wigs and corporate people.Like what they do to day

I know Gm did a lot of work for the military and the federal government.Now the one thing that can prove your truck came with disc brakes is the build sheet on your glove box i think in 1971 on the4 build sheet it shows it came with disc brakes.

Now I seen a few 1-10 proto type trucks and car's built with special fuechers and add ones that you would not get on any average Joe truck or car look at Elvis the car he bought for his mother if he special ordered that car with disc brakes it would not be on the build sheet it be a dealer add on


Here is another one for strange things that GM did back in 1970 the Monte Carlo had 7 engine combos that could be put into that car but one could only be installed at the dealer

250 inline 6 , 350 standard , 350 Hi Po , 400, 402 big block, LS 6 454 SS modal only, LS 7
with dealer add on alum heads factory never put factory alum heads on any LS 7 engine dealer only and the LS 7 was a rare modal in the Monte Carlo

so Gm will add things on But at the dealer only.Now i know that some of the COPO car's and some trucks have options that are not listed on the build sheet do to there special needs program like the CDF and Fire Department just depends on who ordered the truck.and if so it will have a government Tag on it

[mcbassin]

It wouldn't suprise me at all to see disc brakes on a 70 GM executive truck like Keith said. I would like see some SPIDs of one of these trucks with this option. You 71-72 owners, does your SPID call out disc brakes? If they were standard equipment I would assume you wouldn't see it on the SPID?
I have never personally owned a 71-72 and really don't know that much about them. That's the reason for the question.

[68Gold/white]

Not disputing what anyone says/thinks...

I used to sell auto parts. Disc brakes for 70's was listed as an option. I even sold some. Not terribly common, but was surprised when I brought out a set of shoes, and the customer said it was disc...

Did the rear axle width change, when they went to 5 lug??? and is it the same width as 73-up???
(I'm new here, have a lot of old Chevy pickup knowlwdge, just not sure on this fact. I know the 73-up, rears are wider that my 68 all drum pickup...and that 66 rears are narrower than my 68...)

[too much stuff]

68 gold/white, where did you see it listed as an option? That is what we are trying to find out here.
Also, mid way through 1970 the rear axles went to a wider width. Late 70s had 6 lug with the wider rear. Approx 3" overall i think it was. I think that width held true for awhile.

[68Gold/white]

Originally Posted by too much stuff

68 gold/white, where did you see it listed as an option? That is what we are trying to find out here.
Also, mid way through 1970 the rear axles went to a wider width. Late 70s had 6 lug with the wider rear. Approx 3" overall i think it was. I think that width held true for awhile.

I sold auto parts in an independent auto parts store, not NAPA or such. I will see if I can find an old catalog. Probably Wagner Brakes parts.
I know aftermarket info is the least believeable, but many times, had it correct.

[ls1nova71]

In 1970 Impala's were offered in either drum brakes (standard) or front disc (optional), they use the same size/bolt pattern studs as the trucks. It's my guess that this is why the GM book states '70 disc and '71-'72 all. Are we sure the book is only for trucks?

[lolife99]

Originally Posted by ls1nova71

In 1970 Impala's were offered in either drum brakes (standard) or front disc (optional), they use the same size/bolt pattern studs as the trucks. It's my guess that this is why the GM book states '70 disc and '71-'72 all. Are we sure the book is only for trucks?

Excellent point.