1966 Differential Cover Dates. Post what you have!

[Chris T.]

Re: 1966 Differential Cover Dates. Post what you have!

Mike,
November 1, 1965 built car. Diff. cover dated I 16 5.
Chris

[Mike B.]

Re: 1966 Differential Cover Dates. Post what you have!

Excellent Chris,

So another #3871375 cover from an early November built car has an I 16 5 date. Wow. This is getting very interesting!

[Vernon S.]

Re: 1966 Differential Cover Dates. Post what you have!

Hi Mike,

My Nov. 5,1965 built L-36 also has I165 cover.

Skip

[Mike B.]

Re: 1966 Differential Cover Dates. Post what you have!

Good Morning Skip,

Thanks for the response! Check out post #1 to this thread. I show three photos of L36 posi unit covers. The first two are from very early November built cars. November 5th and 9th. These pics were stored in my "filed photos." I wasn't sure who the November owners were. Now I've just figured it out. The top most pic is your '66 L36 and the next one down must be Peter Martin's L36? Two very highly optioned cars .

Here's that photo again of your car's cover for clarity. Sorry for this mix up Skip. What do you think of all of the I 16 5 responses so far? This is why I began this thread. I'm wondering just how many later built '66 cars have dated covers? Are dated covers mostly from the very early built '66 cars? Maybe a lot more folks will see this thread and respond.

Photos are great but not necessary. Just tell us all what you read there and when your car was built. Please respond too if you read no date there. That's just as important as dated cover information.

Thanks, Mike
1. Nov 5th built '66 L36 with Sep 16th dated cover (I-16-5).jpg

[E S.]

Re: 1966 Differential Cover Dates. Post what you have!

Hi- Mike-Look at my post-(#13)-Then look at your post-(#19)-If I am seeing them correctly, the casting dates are inverted!
What goes? Two foundries?
E.J.

[Mike B.]

Re: 1966 Differential Cover Dates. Post what you have!

E J,

You're right! The casting date on your cover is inverted? Or the other two early November covers are inverted? See post #1. Thanks for pointing out this anomaly. Or maybe this is more common than we know?

Mike

Hi- Mike-Look at my post-(#13)-Then look at your post-(#19)-If I am seeing them correctly, the casting dates are inverted!
What goes? Two foundries?
E.J.

[E S.]

Re: 1966 Differential Cover Dates. Post what you have!

E J,

You're right! The casting date on your cover is inverted? Or the other two early November covers are inverted? See post #1. Thanks for pointing out this anomaly. Or maybe this is more common than we know?

Mike

Mike- Do you have a picture of another L72 cover?
E.J.

[Mike T.]

Re: 1966 Differential Cover Dates. Post what you have!

Hey Guys - Just crawled under my 66 L72, late June 66 buildDSCN6574.jpg, and the rear cover shows no raised date codes at all.
Uh, disregard the big Yellow Paint Blob, done by the PO when they did a body-off back in the early 90s.
IMG_7774.jpg

[Patrick B.]

Re: 1966 Differential Cover Dates. Post what you have!

Maybe they had more than 1 wooden form to make the molds, and the date tags were screwed on with a random orientation. It seems that a lot of covers were cast on that day.

[Mark M.]

Re: 1966 Differential Cover Dates. Post what you have!

I agree with you Patrick. As John Hinckley had explained there were production demands that required multiple patterns which were used to make the sand molds for many of the casting type parts. It's noticeable that many parts were made in batches. The patterns had types of identification if there was an issue. Stingray rear end covers have a pattern number easily seen on the bottom rear flange edge above the center top of the spring. The spare tire carrier blocks the view some. Cover pattern numbers often have GM and a number. I not sure if it was the warren, Mi. plant casting these, but they must have seen a need for adding dates in 66. It would interesting to know some of the pattern numbers in this survey.

[Mike B.]

Re: 1966 Differential Cover Dates. Post what you have!

Hi E J,

Sorry, but I don't have any other dated L72 cover photos. But I'm hoping that others with or without dated covers will respond to this thread. Small block or big block cars makes no difference. As long as it's original to the car. Should be a #3871375 casting number.

[Mike B.]

Re: 1966 Differential Cover Dates. Post what you have!

Mike,

Thanks for the great shots of your late L72 cover along with your posi assembly date. Your undated cover is falling in line with other later differential covers.

[Mike B.]

Re: 1966 Differential Cover Dates. Post what you have!

Hi Pat,

I'd really like to see an example of the wooden form you mention in your post here. I've seen other anomalies with missing casting number digits. One example I recently saw on eBay showed a '66 cover casting number of 38713 5. The last 7 was not formed at all.

Wish I'd grabbed that photo. I'm searching for it now. I'll post it here if I can find it.

Mike

[Mike B.]

Re: 1966 Differential Cover Dates. Post what you have!

Hi Mark,

I've never heard of differential housing pattern numbers. I've got 2 separate differential units up north. One small block and one big block. I'd really like to know what these numbers look like. I'll check mine when I get back up there.

I know it's common to see the two letter ID stamped alone on the upper surface of the housing. "AU" for heavy duty 3.36....."FB" for heavy duty 4.11 and so on. These match what's stamped on the lower assembly date flange. This upper number isn't visible without removing the differential.

Thanks for this info,
Mike

[Mike B.]

Re: 1966 Differential Cover Dates. Post what you have!

Here's that upper ratio stamp. This one's "AZ" HD 3.55 Corvette late June assembly dated. And it shows the missing "7" in the cover casting number discussed earlier.

HD 3.55 Late '66 Posi Unit (1).jpgHD 3.55 Late '66 Posi Unit (2).jpg