Differential Color

[sixt9x33rs]

I cleaned up my rear end and it appears that the differential never had any paint on it. The axle tubes were black. Is it possible that the differential did not get any black paint?

Check out the "X" and the differential.

[69Z28-RS]

Generally, GM's assembly plants did not paint heavy thick steel/iron parts as part of the chassis.   They got installed as supplied by the vendors.  Their vendors generally shipped such parts unpainted, or with a coat of 'chassis black' on them purely to keep them from rusting before installation on the production line.   After that, the part is heavy enough it's not going to rust thru during the warranty period, so they didn't seem to worrry about it.  In looking at 30-40 yr old parts, it's difficult to know if that part ever had the chassis black sprayed on it or not, because generally that paint mostly got 'washed/worn' off' from being on the road..  Most 'judging' organizations accept either cast color, clear coated (to prevent rust), or even a 'chassis black' coating on those types of parts ...

69Z28-RS
 

[william]

Camaro rear axles were painted a glossy black after assembly, including brake drums. The pinion yoke was masked; brake lines were not in place at that point. As there was no surface prep the paint did not adhere very well.

Hers's a vintage photo of ZL-1 #3 as received at the dealer in 1969.

[sixt9x33rs]

Great Pic, thanks William. I will go back and put the "X" on it.

[william]

Any markings found on the axle were put there prior to paint and would not be visible afterwards. Paint was the LAST operation in manufacturing; they also added an axle code label to the face of each brake drum shown on page 166 of Jerry MacNeishs' 1969 book.

[69 4 Speed]

Did the ZL1 come with the muffler configuration as in the picture above? I thought all 69 Camaros came with the cross flow muffler or chambered exhaust mounted behind the diff. Then again, I'm not fluent in all things ZL1.  Thanks.

[william]

For '69, Z/28 and Camaro SS with 350 & 375 hp 396 engines initially had, as standard equipment, the new chambered dual exhaust system. Very quickly some owners were being ticketed for "excessive noise" in areas that had such laws. By November '68 Chevrolet dropped chambered as standard equipment and issued a voluntary recall of affected cars. Owners could have the entire system replaced at no cost with the standard dual exhaust system. There were two categories of the recall:

Z/28s built with chambered exhaust were initially retrofitted with a version of the '68 "deep-tone" dual exhaust system. This system had a unique transverse muffler, no resonators.

Camaro SS with 350 & 375 hp 396 engines were retrofitted with the same system as used on the 325 hp 396 engine. That was essentially the same system used on the 300/350; a transverse muffler with two resonators.

At this time, stuck with lots of inventory, Chevy made chambered exhaust optional on the same cars: NC8 $15.80

The interim Z/28 system was still too noisy for some so on April 15, 1969 Chevy issued an update. The interim system was now to be replaced by the standard muffler/resonator system as used on the 300/350.

In May '69 Chevy made more changes. NC8 was dropped as an option and the standard dual exhaust system now included chromed tailpipes. All dual exhuast equipped cars had a price increase of $15.80.

COPO Camaro production started after the chambered recall took place. Most ZL-1 & L-72 Camaros received the standard muffler/resonator system. A few ZL-1s are known to have been ordered & built with NC8; some L-72s may have also.

It sounded mean but with 4 muffler sections chambered exhaust was actually more restrictive than the standard muffler/resonator system.

[sixt9x33rs]

Any markings found on the axle were put there prior to paint and would not be visible afterwards. Paint was the LAST operation in manufacturing; they also added an axle code label to the face of each brake drum shown on page 166 of Jerry MacNeishs' 1969 book.

So that "x" on the differential would suggest that this part of the axle did not get any paint? It looked that way

[69Z28-RS]

.....  (portions deleted)
It sounded mean but with 4 muffler sections chambered exhaust was actually more restrictive than the standard muffler/resonator system.

Has anyone ever tried/ran just the rear most chambered exhaust sections?   John Z had told me a few years ago that the full chambered system was actually more restrictive than the standard muffler, but I love the chambered sound..   I bought all the chambered pipes in 1976, before I realized my late car couldn't have come with it... 
 

[william]

So that "x" on the differential would suggest that this part of the axle did not get any paint? It looked that way

It might look that way after 43 years but photos at the assembly plants show complete paint coverage. I know Firebird axles had sloppy paint coverage; Pontiac did those. The paint was not there for appearance; it was simply short-term rust preventative. I have been involved with the cars for 36 years; not unusual to see no paint left on anything under cars up here. No surface prep, no primer.

[sixt9x33rs]

So that "x" on the differential would suggest that this part of the axle did not get any paint? It looked that way

It might look that way after 43 years but photos at the assembly plants show complete paint coverage. I know Firebird axles had sloppy paint coverage; Pontiac did those. The paint was not there for appearance; it was simply short-term rust preventative. I have been involved with the cars for 36 years; not unusual to see no paint left on anything under cars up here. No surface prep, no primer. perhaps the black paint wore off around "x"?

[william]

The term paint is used here loosely. I don't know that the black coating applied to rear axles was paint at all-it may have been the same asphalt-based stuff they used on frames.

The X is there to indicate an important step was completed; its location suggests pinion bearing pre-load. There was probably a small can of white enamel at the workstation with a dauber in it. When that step was completed the operator painted the X on the top of the housing.

BTW I see remnants of the black coating in your photos.

[sixt9x33rs]

I agree there were remnants of black but not prevelant in the immediate location of the "X". Probably was at sometime. The black you may see close to the "X" are grease and oil clods.

[MO]

1. It would be incorrect to paint the "X" over the black paint. Yet this is done regularly on over-restored cars.
2. Heat is the major contributor to paint failure. If you look at original calipers, you will see the same paint characteristics; signs of paint, but yet they look bare overall.