rear differential detailing
 

Was the complete differential painted black from the factory or was any of it natural cast iron or bare metal? thanks for any info.

It varied by plant and year. A lot of survivor cars I have seen seem to have had the cast iron components painted only on the back side (facing the gas tank).

….and by shift and by operator.

Just to expand on what North saying: the application was pretty haphazard so there would likely be bare spots opposite of where the operator was standing and spraying.

K

Oldsmobile Lansing plant shown, but this will give you an idea.

This guy starts at the front of the chassis and works his way rearward, drizzling the chassis black in the general direction of the frame as he goes.

K

http://forums.maxperformanceinc.com/...1&d=1602685017

I've been working on making my 68 bird as correct as possible. The rearends for 1st Gen cars were not installed when they were painted. While I can appreciate the picture above, that's for a full frame car. Since the rearends only got paint on the backside, it's 100% correct that the paint on them got varied a lot. I've heard they were painted with the rear springs attached and I've also heard they were painted without the springs attached, so I'm not sure which is correct. For the rearend itself, if you want to do a "fake" correct looking detail job, you can paint the pumpkin with cast iron gray and the tubes and brake backing plates with Stainless Steel color paint. Then paint the backside only with black covering as much as you think might be correct if you were a GM worker (read into that whatever you want). So, you might ask, were the brake backing plates on when the rearend was painted? Again, I don't know for certain. I think, yes they were on the rearend before it got painted black and therefore received the same partial coverage, but I have no absolute proof.

Here is a link to a photo of a 69 bird being assembled at the factory. Looks to me like the springs were assembled to the rearend as well as the backing plates before painting black, but you be the judge of what your eyes are telling you. BTW, the springs were gray phosphated prior to all of this.

OJ

Woops...... forgot the link: https://www.ebay.com/c/28022510633

Since I worked for GM for almost 40 years, in product design and a dozen different vehicle assembly plants, let me see if I can help your understanding a bit:

Doesn't matter. I'm trying to show you that the concept is the same.

Even though the 'bird is a unibody construction, the front suspension and rear suspension are processed in vehicle position by using the "tow-veyer", which allows you to install the brake lines ahead of body marriage and maintains the correct spacing through the process. That technique was used on early unibody vehicles like the Corvair and is still in use today building unibody vehicles.

You can get a visualization of that in the photo that you have referenced (which I am familiar with - the author of the link I am about to provide is in the photo).

You might also note in the photo that there is a Chevrolet B body on the line directly in front of the subject red bird. That's a full frame vehicle, further proof that the process was exactly the same since they were going down the same line.

Rear brake backing plates (and brake assemblies) absolutely were installed on the rear axle. The rear axle was received as an assembly, drum to drum. The appropriate axle was picked off the rack based on the build sheet and placed on the axle subassembly line, brake lines installed, drive shaft selected, and then conveyed to the main line in sequence.

I would suggest you get familiar with this website, if you are not already. It's written for Camaro, but Norwood built Firebirds as well. Although there will be some plant-to-plant variation it's probably the best and most detailed summary I've ever seen.

http://www.camaros.org/assemblyprocess.shtml

K

'61 Tempest (Pontiac Michigan plant):

http://forums.maxperformanceinc.com/...1&d=1390154032

http://i23.photobucket.com/albums/b3...9-Assembly.jpg

http://i23.photobucket.com/albums/b3...01/Corvair.jpg

http://i1016.photobucket.com/albums/...ps87f49a70.jpg

Quite a bit of general discussion (A body related) in this thread, too:

http://forums.maxperformanceinc.com/...ht=constraints

The factory assembly manual specifies that the brake backing plates are NOT to be painted. The paint on the tubes is to end about an inch away from the backing plates.

This is how I do them at
Pure Stock Auto Restorations Inc

Axle here is original 3.42 OO code posi rear axle in a customer's 1970 Buick GS Stage 1.

I will post some pics of 1969 GTO Judge axle later.

There are a lot of variations when it comes to restored vs original. Especially true with regards to colors, plating, gloss and black-out.
Model, year, plant had variations in the process + the human factor; One Operator sprays differently than the next Operator.

At least for '67-'69 Firebirds, the Axle was not fully blacked-out; mostly just the rear facing side was hit with paint as well as some overspray on the backing plates as evident in '69 Lordstown pix above.

Another variation I often see at shows is the Upper Control Arm Shaft Hardware. More often than not, these will be shiny zinc plated washers & bolts. Shaft is often left natural (or painted to appear natural).
However, reference pix from factory, magazine road tests and low-mile original, survivor, unrestored cars show these were painted black. Only the attaching nuts and shims (to subframe) would have been natural or zinc.
According to CRG site (John Z), the Control Arms were dip painted, with the Shaft/Hardware in place.
https://live.staticflickr.com/65535/...ae08d831_b.jpg

Also interesting in that pic from Van Nuys that the end of the tailpipe is black, looks like it was dipped?