rear end cover

[Mike M.]

I have a 65 the rear end cover and it has a casting number 3871375. I can't find a date. Where these not dated. Also what years does this casting cover. Thanks Mike

[Wayne M.]

Re: '65 rear end cover

Mike --- All's O.K. in the great white north; In spite of what the '65 tech manual and judging guide says, there is NO casting date on the rear diff cover flange (forward of the oil plug) prior to 1968 MY. I have two original examples in my garage (AU from a mid-'67 and the FA on my late '65).

[Mike M.]

Re: rear end cover

Hi Wayne, I just checked my rear cover again and it has a number on it and it ends in 375 like the judging manual says on the rear of the cover. The numbers before the 375 are diffucult to make out.Any ideas what this number stands for. Thanks Mike

[Wayne M.]

Re: rear end cover

Mike --- It's probably the cast # 3871375, on the upper edge of the diff cover flange (where the diff bolts to the cross-member) and it's upside down. On the opposite flange, there will be a cast "GM x", where I think x is the mold #. If you have the cover off, you will also notice a cast "375" inside, on the concave surface, as well as an embossed casting digit (in my case, it matches the mold #). I'm describing the insides of the '67 (which I have apart).

[Gary B.]

Some 66 covers are dated; other aren't

Mike,

You might want to check in the archives for a posting on this topic about 2-3 months ago. Some people with original cars report dated covers for years prior to 1968, e.g., 1966. I could never figure out if there was a pattern about dated covers, but some covers have dates and other contemporary ones don't. The original cover on my '66 with a July build date is not dated, but I've heard from other '66 owners with earlier build dates who do have dated covers. Please let me know if you find out any definitive information. I'm curious.

Gary

[Gary B.]

Prior postings on this topic; some '65 were dated

Mike,

The previous postings on this topic took place between Nov. 30 and Dec 30, 1999. Please check the archives. One posting said the following:

************************************************** ********************* Re: Help w/ casting dates from 63-67 owners Posted By: Wayne Womble (spider-tm034.proxy.aol.com) Date: Wednesday, 1 December 1999, at 9:34 p.m.

In Response To: Help w/ casting dates from 63-67 owners (Gary B.)

Just looked a one today, a 65 370 gear, the rear was assembled 9-22-65 . The casting date was H 26 5, located on the flange directly foward of the filler hole. ************************************************** ***********************

[Mike M.]

Re: Prior postings on this topic; some '65 were da

I just read the prior postings .It looks like the rear end covers for 65's only had a casting number which should be 3871375. No casting date till later years. Thanks Mike

[Joe L.]

Re: rear end cover

Mike-----

The GM PART #3871374 differential carrier housing cover(CASTING #3871375)was used from, at least, 1964 through 1977. It may also have been used for 1963; I'll have to check that possibility later. For 1978(and POSSIBLY very late 1977) the cover design was changed somewhat. The new cover was GM PART #464909(I believe casting #464910). This cover was designed around the use of 7/16" spring attaching bolts in contrast to the 9/16" bolts used earlier on the 3871374 cover. This change was made to accomodate the new 2-1/2" wide rear leaf spring used on these later models; earlier springs were, of course, 2-1/4" wide.

In the late 70s, the 3871374 cover was discontinued and the GM #464909 cover replaced it for SERVICE of all 63-79 Corvettes. When used on 1977 and prior years, though, the spring retainer plate and 4 spring retainer bolts had to also be replaced if the 464909 cover were to be used. In addition, 2 spacers had to be added on either side of the spring. These spacers were GM #459032 and are discontinued.

As far as date coding goes, I can tell you that my original 69 cover has no date codes appearing on it. I have several others of these covers, though, including 1 which I know originated from a 1976 model car. I will check that cover when I get a chance and report.

[Wayne M.]

Re: rear end cover

Mike, Joe, Gary --- First, let me correct my faulty reading of the '65 Tech Manual. It does NOT say there are dates on the diff cover; (anyway the castings are not judged). The '65 TM/JG talks about the cover cast #; then next sentence says casting DATE, but you have to know your differentials to realize they have switched to talking about the carrier, not the cover.

The thread on the subject of dated covers, back 4 or 5 months, was inconclusive (IMO). RESTORER articles (Winter '86, Summer '7=87) discuss every cast/stamp/crayon mark on C2 carriers and covers, and NOT ONCE do they mention cast dates on the covers.

[Tom B.]

Re: rear end cover

From what I remember also Wayne, it was inconclusive. A couple reportedly had dates prior to 68 and a couple didn't. I know my 68 cover has a date, but I never did check my 67. I'll see what I can find out, too. TBarr #24014

[Robert C.]

Re: rear end cover

Could it be?? the rear end cover was just part of the rear end ASSEMBLY, therefore it has no date.The assembly has it's date on the bottom flange. If you bust off an ear and need a NEW rear cover from the parts dept at GM dealers, maybe they were dated. ???

[Joe L.]

Re: rear end cover

Bob-----

It's within the realm of possibility, but I seriously doubt it. First of all, the purpose for the casting dates was to allow GM to "zero-in" on foundry problems. For instance, if a large number of rear end covers failed and all were produced on or about the same day, their quality control folks could use this information in "tracking down the source of the problem". Presumably, finding out the reason(s) could prevent future occurences with the resultant warranty costs and unhappy customers. The dates WERE NOT applied to castings so that some future restorers could "date-match" components on their cars for "judging" purposes.

Since the carrier housings and carrier covers were obviously cast seperately, and since the purpose of the date codes was not for the purpose of dating the assembly(usually, if that's important, the assembly will be date coded by stamping at the time of component assembly) and since the ability to "zero-in" on casting anomolies would be equally and independently applicable to the carrier housing and cover, I suspect that the reason that the covers usually didn't have the date is not related to the fact that they were part of an assembly.

Secondly, usually PRODUCTION and SERVICE parts of the same part number are produced at the same time; some are sent directly to component assembly for PRODUCTION use and some go to GMSPO for SERVICE use. I really doubt that the foundry would have cast the ones for PRODUCTION without dates and the ones for SERVICE with dates. Generally, GM would be more concerned about dates on the pieces destined for PRODUCTION use since new-vehicle customer satisfaction and warranty claims were at stake and tracking down problems a much higher priority than with SERVICE parts.

There are many instances where certain castings have dates and others don't. Most suspension component castings don't have dates with the exception of rear spindle supports which do. Some exhaust manifolds have dates, others don't. Sometimes, even exhaust manifolds of the same casting number have them and others don't, usually a factor of the era in which they were produced. What the reasons for this inconsistency are is unknown to me.

[Gary B.]

Date codes are indeed on the rear cover

Mike,

In Wayne Womble's posting from Dec 1, he is talking about a date code on the cover, not on the main housing. Some mid-year rear covers do seem to have date codes.

Gary

[Wayne W.]

Never Say Never

My experience is that every time you say Never you are Never Right. I have seen Many early covers dated you can go back to my post. The one stated is an early 66 BB It definitely has a date.

[Joe L.]

Re: Never Say Never

Wayne-----

Am I missing something here? Where did I say that early covers NEVER had the casting dates?