'64 rear end cover

[Gary D.]

I'm trying to locate info on casting number 3830303, diff cover on my '64
coupe. Carrier stamp shows "CB", 3.36:1 Posi. Spring mounting bosses are
broken, and the catalogs seem to show regular replacements, or "heavy duty".
Is breakage a common problem with the stock ones? I actually have another
cover with same casting number, but not sure if that's correct for year, or if
"heavy duty" is way to go. The car is basically a 365 hp, 327 that is
original /restored condition for the most part. Thanks in advance for any
thoughts and info.

Gary

[Joe L.]

Re: '64 rear end cover

Gary------

The GM #3830303 is the correct casting for the differential cover for your 1964. Whether the spare one that you have is "correct" for the car depends upon the date code cast into it. For NCRS/NCCB judging purposes, the date should fall within 6 months prior to the build date of the car. However, I don't know if these dates are actually judged, or not. Any 1963-79 differential cover will work for you application, but only the 63-76, of which there were at least 3 casting numbers including your 3830303, will have the 9/16" spring retainer bolt tappings.

In general, the stock covers are strong enough. Usually, if the cover spring bolt bosses are broken, it's due to improper installation of a spring rather than breakage on the car. I'm not ware of these ears breaking in service/ However, MANY are broken due to failure to de-arch the spring prior to installation and torquing of the 4 spring mount bolts.

The aftermarket heavy duty covers are fine, though, except for the originality issues, if that's important to you. Also, many of the "heavy duty" versions of the aftermarket covers do not have sufficient arch in the rear section of the cover to allow for proper installation of the spare tire carrier. They get their "extra strength" by much beefier rear casting configuration and, sometimes, what is lost is proper clearance for the rear tire carrier.

[Steve L.]

Re: '64 rear end cover

My lugs are broken on a 73. I've had the car since new and I know that the rear was never touched since the factory. The car was never raced or abused except for once that I drove down a regular curb that I didn't see one dark rainy night in a parking lot

Anyone know if these lugs can be welded?

Steve L
73 coupe since new

[Joe L.]

Re: '64 rear end cover

Steve-----

Actually, as I mentioned, I've heard of few of these covers that have actually broken in service. However, perhaps this is more common than I believed. My original owner 69 with 200,000 miles on it still has the original cover. And, in my case, the cover (and spring) have been off the car several times for various restoration projects (most of which have been unneccessary, but that's another story).

In any event, I would not recommend trying to repair one of these covers. They are cast from nodular cast iron and, in my opinion, it's just too problematic to try to weld-repair this type of material, especially for an application which does require high strength. Plus, these covers are too plentiful in the used market to get involved with a repair of a broken one.

As I mentioned, except for the aspect of originality, the aftermarket covers are just fine. Some are available that will provide proper clearance for the spare tire carrier although these are not the "max heavy duty" type. But, they'll be stronger than the originals in both design and material. The aftermarket covers are cast from a higher strength cast iron alloy than the original covers. Metallurgy has improved since the 60's and 70's allowing for such improvement in the covers.