70 5 lug disc brake thread
 

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 :chevy:

Re: 70 5 lug disc brake thread
 

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

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

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

Re: 70 5 lug disc brake thread
 

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

Re: 70 5 lug disc brake thread
 

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

Re: 70 5 lug disc brake thread
 

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

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

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

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

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! :lol:

Re: 70 5 lug disc brake thread
 

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,...

Re: 70 5 lug disc brake thread
 

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

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

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...)

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

Ok guys I come to find out today that I am the fourth owner. The original owner handed it to his son and he is the one that painted it and so on. The guy I bought it from was the third and I am the fourth. I did state that I have in my 42+ years seen several 70's with disc. With this said I did not mean that I saw them rolling all over town. I was told by my buddy that these were optioned in 70 with 5 lug disc years ago and have been under the assumption that they were in the more late 70's run highly optioned trucks offered with 5 lug disc. With this information told to me by a highly reputable GM parts manager in this area thats is what I have based my thoughts on. I will try and get in touch with him in the morning when I get off and see if he can dig up some info and scan the part where it says these studs were 70,71,72. As far as me getting all of the info on my truck that some of you have asked for, I will as soon as I get a chance. With all this being said I never have in my life claimed to know it all and never will and if I am wrong about this then I am a grown enough man to admit it.


PT

Re: 70 5 lug disc brake thread
 

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.

Re: 70 5 lug disc brake thread
 

OhOneWS6, I want you to feel free to comment but just keep in mind that like Tim said there is alot to be learned on this site. It has been to my understanding that the 5 lug disc was an option for many years, this is what I have been told and this is what I think is true. I have also always thought that my trucks one of the optioned trucks but with a spid that has been painted over and not alot of data to prove it I just never said anything. I have seen a few at some local cruise arounds and stuff that the owners as well think the same. I never disputed it and was just to the understanding that this was true. I will do everything that I can on my part to try and prove this to be fact and if it is not then I have been misled for many years. All of your comments are welcome by me but just keep in mind where I am coming from. As Tim (SpecialK) stated there are alot of things on these trucks that folks have seen that are not in any data books or one says his came with and another says no way. This is what this site is here for and this has became a mission for me. So with this said your positive comments are welcome.


Thanks PT

Re: 70 5 lug disc brake thread
 

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

Re: 70 5 lug disc brake thread
 

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.:metal:

Re: 70 5 lug disc brake thread
 

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?

Re: 70 5 lug disc brake thread
 

Excellent point.

Re: 70 5 lug disc brake thread
 

Guys I called my buddy at the dealership this morning and he is going to do some indebted research on this and told me to call him in the morning. He has access to all of his old parts manuals from the 60's and 70's. He said that he would try and do some research and give me some data tomorrow. Do not shoot me yet fellows, I have one more night of 12's and then I will be off for 7 days to take a look at my truck.


PT

Re: 70 5 lug disc brake thread
 

The 70 Impala bolt circle was 5 X 4-3/4, for disc and drum. Pickups were 5X5.

Disc brakes were an option for Impala's starting in 1967.

These were the 4 piston Corvette style calipers, and used them into 1968. Sometime in 1968 they changed to the single piston calipers, that was used through 1970

The single piston caliper disc setup was an option from mid 68 through1970. The 1965-1970 Impla'a were built on the same platform.
71-76 used a different platform. AND the 71-76 used the same rotors as the 1/2 pickups, 5X5 pattern...

I'm not trying to start an arguement, I had a 67 Impala, put disc setup on it from a 1970 Impala.
The 71-76 Impala's were entirely different cars.

65-70 were rear steer, all 4-3/4 bolt circle (drum OR disc)

71-76 were front steer 5x5 pattern, ALL 71-76 were disc, NO drums on front

PT, your research will show all this!!!

Re: 70 5 lug disc brake thread
 

To all, Sorry for the snap. Had a bad day. Just had back surgery 2 weeks ago and I am still a little out of sorts. It's not an excuse just an explanation. I agree that is it possible that it was an option. Will watch quietly from my corner. :beers:

Re: 70 5 lug disc brake thread
 

Email communication can have the emotional twist, that each receiver of such can take, any direction.....Yee Ha!!!


Only one was perfect, his birthday is Sunday!!!

Re: 70 5 lug disc brake thread
 

Very well said 68Gold/white. No feelings hurt here. Hope you get that back to feeling better.


PT

Re: 70 5 lug disc brake thread
 

I perceived no ill will towards me. I'm just trying to help.. :)

I worked in an auto parts store for 13 years, now I do truck stuff. I worked for an independent auto parts store, not a chain. We did a lot of business, I learned a lot. Also learned a lot from working on m own stuff, sometimes helping a customer after quitting time....

GM usually did things that made sense, and looking at most of their parts, the parts were usually engineered to do the job.
HOWEVER 11X2 shoes on the front of a half ton pickup from 1960 till 1970 was a very poor deal.

I know I've sold parts for some 1970 C-10's w/ disc, not many...

Ford had so many stinking better ideas, it was difficult to keep up with. Going with a completely different part in the middle of the year, is insane. AND neither part usually performed the job very well. You'd of thought the later part was a major improvement, NOT.

This Ford rant is a generalization. They did this kind of thing w/ all kinds/types of parts. It wasn't something that happened every day, but you usually didn't have the info to tell where you were in relation to the stop/start date.........

Re: 70 5 lug disc brake thread
 

I have been working on these trucks since they were new and I have never seen a 70 with disc, not to mean that there were never any built. I did some research, though, and Napa does not list disc for a 70, but O'Reilleys does!!

Re: 70 5 lug disc brake thread
 

That's why in a earlier post I mentioned aftermarket parts sources as possibly being a less believeable source than O.E.
Every time we switched makes of a particular type of parts, I wouldn't let go of the old catalogs, if possible.

It's really a gas to walk in a parts store these days and ask for a part. The young person behind the counter asks all the questions the computer generates.........
Like on a front wheel car, if it has a TH400 trans....LOL...LOL

When the chains started showing up. We'd call them, ask something like..."Do you have a brass magnet, and how much???? :D

Re: 70 5 lug disc brake thread
 

Yes,GM uses a separate catalog for trucks. This comes from the 46-72 Chevrolet Truck Parts Catalog. We know there are exceptions. But,what is odd here is there is a parts listing. Generally with any exception you won't find that,due to the unique nature. If a part was borrowed from another vehicle then that is where the part number will take you.

Re: 70 5 lug disc brake thread
 

I was looking at my 46-72 catalog last night and it had the 72 plastic door panels listed as "71-72" so perhaps the catalog had its gaps or all changes didn't coincide with the model year? I realize your point it that the parts listing only adds credibility and I agree with that, guess the point i'm making is that there is no way to know for sure unless the build sheet or date code is found and I think that is what you're saying too?

Re: 70 5 lug disc brake thread
 

factory books aren't always right.... Tim's 4 speed highlander was a good example, but a more common example was the books saying no 3.07 gear limited slip rears in 67 - 72 trucks. Yet there's been about eleventy billion SPIDS shown here.
Parts stores listings are not good reference IMO... NAPA shows that big blocks were not avalible in a 72 burb... but they show it for a 1/2 ton burb. Most all parts stores don't show a 305 nor 351 V6 in GMC trucks.

71/72 SPIDs do not show disks. The SPID only shows an option, not a standard/base equipment item.

While I have been proven wrong time and time again on here (and I could be wrong on this) I'm pretty sure there were no 5 lug discs in 70. If it was an option, they would have advertised it. It would have been more common too.
Anotherr answer to this oddity is that it was swapped out many many years ago and someone forgot. There's a member on here with a 2 owner 71/72 GMC with a 68/70 grill. He swore up and down it was original and that's how his dad got it (first owner). It had been wrecked way back in the day and the body shop put the older style grill on it. His dad still said no way, it was the same style grill, and he finally showed his dad old family photos showing the truck with the correct grill. The timeline typed out on this truck in question here, the second owner, the one who painted it, may well have forgotten to mention this modification.

I'm just finding it a tough one to swallow, hardly anyone has heard of this for 40 plus years and here it is. I personally think this one is like the small window '68, and the 'ss' trucks you always hear about... and the 'special ordered vette motor'.

Re: 70 5 lug disc brake thread
 

Ok, I thought that the '70 Impala's were 5x5, but I guess I was thinking '71 and up, because I used to see truck rallys on them all the time. But I have to agree, that with tens of thousands of members on here, if it was true that discs were available in '70 on a truck, somebody would have come up with some difinitive proof by now. I've been a naysayer of other threads on here before, but I've also been around these trucks for better than 20 years. Not saying I have seen it all, but have seen alot and without a build sheet or a SPID (which now days are fairly easily reproduced) I'm going to stand my ground, after all I'm from Missouri, the "show-me state".

Re: 70 5 lug disc brake thread
 

Thanks for clearing this up for me Longhorn. I always wondered about the SPID. I have a 1970 with a "396" on my SPID but I know from research it's actually a 402. GM has done some crazy things on these trucks.
Anyone out there have a 1970 SPID showing disc brakes?