Don O.

What is the proper color for the differential, pumpkin, chunk etc for a 1957?
Thanks, Don

jim lockwood

I'll be interested in the answer to this, too. On '57 passenger cars, the pumpkin is reddish primer.

Geralds57

DZAUTO

In those days, Corvettes ONLY got (complete) rearends from the Detroit Gear and Axle plant. As the various parts of the rearends (center section, axle housing, backing plates, etc, etc) they got SOME paint applied and in different colors (yellow, blue, green, white, etc). The various daubs and stripes of colors indicated inspections, torques specs, etc had been completed (NONE, I mean NONE of the NCRS community has yet to explain what is indicated, and where specific colors were meant). For example, a yellow paint circle has been seen around the rearend filler plug on LOTS of axle housings, as well as various yellow stripes------------------------BUT WHAT EXACTLY DO EACH COLOR AND STRIPE MEAN?????????????????
When completed at the Detroit plant, the assembled axle housing was shipped to the St. Louis assembly plant (both pass car and Corvette rears).
On the CHASSIS assembly line-------------------BEFORE body drop----------------THE ENTIRE ASSEMBLED CHASSIS (less engine/transmission) was painted chassis black. Depending on the hourly wage earner with the paint gun in his hand, some chassis got thoroughly painted with chassis black, and some did not get completely painted. Thus, some of the various colors applied at the Detroit plant could still be seen.

Now, regarding the red oxide paint on 57 rearend center sections. I've been building/rebuilding these early rearends (55-64) for 50+yrs. Here is what I have observed. The 55/56/mid-57 rearend center sections were painted (inside and out) at the Detroit plant BEFORE parts were assembled into the outer case. . It seems that SOMETIME later in the 57 model year, Detroit stopped painting the rearend center sections with the red oxide paint. ALSO, the 55/mid-57 NON-POSI differential was painted red-----------BEFORE the ring gear was bolted to the differential flange (this makes me wonder if they quit painting the red when posi was introduced in Dec 57???) After that, everything got a light coat of black---OUTSIDE, bare metal inside the case.
I have found a red primer at ACE Hardware that VERY CLOSELY duplicates the red oxide paint for customers who want their rear painted.

This is the inside of a VIRGIN, early 57 NON-posi case after I cleaned it up in the parts washer. Notice the yellow paint circle-----------------------WHAT DOES IT MEAN?????????????????
.


This is the outside of the same case--------------------------WHAT DO THE COLORS MEAN?????????????????






This is the same case after painting and duplicating the colors (per the customer's request---------------I would not have done it).
The difference in the two shades of reds below is because one was taken with a flash and the other without a flash. SORRY!

jim lockwood

Tom, for whatever it's worth, the center section of my '57 passenger car retained unmistakable remnants of the red oxide primer and my car is extremely late '57 production.

Jim

Critter1

I'm definitely not a C1 expert but I think the entire differential assembly, including brake drums/backing plates and center section was coated with chassis black before it was delivered to the St Louis assembly plant. Or possibly coated in the basement of St Louis before being hoisted to the assembly floor. There are quite a few good pictures of the complete assembly showing complete coverage of black on everything.
There may be some pictures in the Noland Adams book?

DZAUTO

I failed to point that out. It SEEMS you car correct. BEFORE shipping the assembled rearend to various assembly plants, the assembled rearends were painted black at the Detroit plant, Then it got a second coat of chassis black on the assembly line at the various plants. For 56 and 57 ONLY, the only difference that I can tell between a pass car housing and a Corvette housing, is the location of where the leaf spring pads are welded onto the axle tubes and the angle at which the 4-hole flange out on the ends of the tubes are welded. The Vette and pass car flanges are exactly the same, but are positioned at different angles prior to welding.
The 57-58 Corvette axle housings seem to be the same, BUUUUUUUUUUUUUUT, even though the 57-58 pass car housings are the same, the 58 pass car housings had trailing arm and coil spring brackets.

Now, with all of that said, is there ANYONE here who can accurately say what and why the different daubs and stripes of colors signify throughout the chassis of these early cars? Over the years I've encountered yellow, white, orange, blue, green, gray.
John Hinkley, how about you?

Panama 58

I agree. Technically here's what you should see. You should see traces of the yellow inspection marks that are showing through a light coat of chassis black. The inspection was done and then there was a final chassis paint light spray done before body placement. If you want to reproduce the correct "judged" look, paint the unit chassis black, apply the correct yellow inspection marks once the chassis black is dry and then a "hit and miss" application of a final chassis black coat.

DZAUTO

Jim,
Does your 57 car have a Detroit or a Buffalo rear?

jim lockwood

No idea, Tom. How do I tell?

DZAUTO

Jim,
Corvettes AND pass cars got rearends from the Detroit Gear and Axle plant.
The rearends from the Buffalo (NY) plant were only installed in pass cars.

As is with engines, heads, manifolds, etc, etc, Detroit rearend cases had only ONE digit in the casting date for the year (example: B77/Feb 7, 1957).
The Buffalo rear casting dates had 2 digits for the year (example: B757).
If it is a posi rear, then the big P on the Detroit case was the thin version and the big P on the Buffalo case was the thick version, as below.


This rear could be from EITHER a Corvette or a pass car.



This rear could ONLY be from a pass car (Buffalo rears DID NOT get installed in Corvettes)..


Now, of course, as was done SOOOOOOOOOO many times with SOOOOOOOOOO many cars, it was quite common to swap, change, replace rearends in these cars. BOTH 55-64 pass cars and 56-62 Vettes share the SAME center section. Thus, who knows for sure what rear was installed in what car, unless a person bought the car new.
Plus, this type rear was quite popular to install in various other cars. Both my 51 Chevy and the T-bucket have this style rearend. I love 'um because they are so easy to work on and change. I probably have about 15 of this style rearend center section under the work bench, from 3.08 to 4.88 ratios.

JohnZ

Tom -

Without digging out and reviewing the late Dale Pearman's (RIP) text from our joint C1 Chassis Restoration Workshops at Bloomington Gold in '02 and '03, I'd categorize the miscellaneous different color markings as having been applied at the different Chevrolet component plants that built the parts, primarily as indicators of in-process inspections.

DZAUTO

I have ZERO argument or disagreement with that. BUT, WHAT do the colors at the different locations mean????????????
If someone (or a group of knowledgeable people) knew WHAT the colors-------------at various locations------------mean, then it would seem that restoration efforts could be more productive and meaningful.

JohnZ

We'll probably never know.

DZAUTO

So far-----------------that's the conclusion that I've arrived at!
So, with that thought in mind ------------------------------AND KEEP IN MIND-------------------------I'm not an NCRS numbers fanatic (even though I've been a member for 40yrs), since it seems NO ONE knows what colors at what locations meant or indicated, then color daubs/stripes can be applied -------------------------------- AND (theoretically) THEY CANNOT BE DISPUTED! If a person has a car on the judging field, and a judge questions a yellow stripe, daub of blue or orange paint, and the owner says "that's what was on the frame/axle housing/front cross member/tie rod end", who is going to dispute it and what, if any, point deduction would be given??????????????
Again, as I mentioned, I am not a numbers fanatic, but after MANY, MANY years of working on old Corvettes, Chevys, Olds, etc, when I've run across stripes and daubs of paint colors, I've always just wondered what the heck they meant.

Here is just one of many examples I'm referring to. This is a front spindle support from a virgin 57 Corvette. This is what I found after cleaning.









This is what I put back on the parts-------------------------I had ZERO clue what the colors meant, but I duplicated them for the owner.

Critter1

I still don't understand what difference it makes since most, or maybe all of the paint swipes are covered in chassis black before the assembly is installed on the chassis.

Some years ago, someone in another country (Germany?) completely disassembled a brand new 61 and took pictures of all of it as it was coming apart. The pictures were posted on line. I don't remember who it was but that would probably show the entire differential assembly.

JohnZ

That was a British motoring magazine, and they tore down a brand new '61 Corvette at the government-owned M.I.R.A. (Motor Industry Research Activity) test/research facility and took hundreds of photographs of all the parts and components. I have that report somewhere, but finding it would be more a matter of luck than anything else.

Critter1

Thanks John. I wasn't sure what country that was done in but I remembered that it wasn't here in the US.