64 rear diff cover

[Ed P.]

64 vette 365 horse has original date coded rear diff cover that someone installed the long bolts in the front holes and cracked the end of the hole on one side causing gear oil to leak. Can this be safely repaired by a welder with cast iron know how. Ed

[Joe L.]

Re: 64 rear diff cover

64 vette 365 horse has original date coded rear diff cover that someone installed the long bolts in the front holes and cracked the end of the hole on one side causing gear oil to leak. Can this be safely repaired by a welder with cast iron know how. Ed

Ed-------


Theoretically, yes. However, personally, I'd never be confident in the durability of such a repair. If you don't plan on driving the car much and don't plan on any long trips, it might be worth a chance, though.

One thing to keep in mind: if the damage is nothing more than a hole without an adjacent crack, it can be repaired by brazing and I think this would be very durable. However, if a crack is present, that's when I would not be comfortable with any repair.

[Russ S.]

Re: 64 rear diff cover

Thirty years ago I broke an ear off my diff cover when changing a spring. I welded the ear back on with the diff still in the car. I have changed spring once since then and the weld is still holding great.

[Joe L.]

Re: 64 rear diff cover

Thirty years ago I broke an ear off my diff cover when changing a spring. I welded the ear back on with the diff still in the car. I have changed spring once since then and the weld is still holding great.

Russ------


Welds in cast iron usually do hold up very well. The main problem is usually cracks developing in areas of the native cast iron adjoining the weld. You may have gotten lucky, but this sort of thing is a very common problem with cast iron welds. Keep in mind that the rear cover is an integral part of the rear suspension of 63-82 Corvettes. The rear suspension is definitely a highly safety-related component of the car. I don't believe in compromising that safety for the sake of retaining an original component.

[Marco H.]

Re: 64 rear diff cover

Ed,
A couple of thoughts; to repair the damage so it has a chance to hold, the cover has to be removed so it can be cleaned properly. A contaminated surface will never give you a usable weld.
it is my understanding, that date codes on rear end covers didn't exist until the 1970's. Not certain, that your cover is original to your car.
Marco

[Gary R.]

Re: 64 rear diff cover

The early covers had a part number cast into them. I don't recall it but show it in my Diff rebuilding threads. The fill plug was different, it was larger and had machine threads. I believe '65 they switched to 3/4 npt plugs. I checked my stock but don't see any 63-64 covers left. A vette parts company will charge more then it's worth- IMO- so if you are going to drive the car and numbers are not that important buy a Muskegon HD cover and be done with it. I would be more concerned with the internals on that 64 diff. If original they were pretty sad, DANA posi's were bad, the pinions were also poorly designed and sheared. Now some one could have gone through it by now but if you drop the diff for the cover take a close look inside, if you're not sure what to look for again look up my thread or contact me and I'll go over it with you.
Gary

[Timothy B.]

Re: 64 rear diff cover

I think the 63-65 covers had a part # that ended with 303. Also, (not 100% sure) the 63 had a fine thread fill plug and the coarse thread plug was used on the 64-5 cover.

[Joe L.]

Re: 64 rear diff cover

I think the 63-65 covers had a part # that ended with 303. Also, (not 100% sure) the 63 had a fine thread fill plug and the coarse thread plug was used on the 64-5 cover.

Timothy------


Yes, the 63 to very early 65 cover was GM casting #3830303. All of these covers used a plug with a machine thread. Later cover used a plug with NPT thread.

[Ed P.]

Re: 64 rear diff cover

Ok thanks for the info I removed the cover today and the entire top of the dome for that hole is cracked in three directions Not even going to attempt a repair. Thanks Ed

[Wayne M.]

Re: 64 rear diff cover

.....Yes, the 63 to very early 65 cover was GM casting #3830303. All of these covers used a plug with a machine thread. Later cover used a plug with NPT thread.

Here's what I believe is the original rear cover off my '65 VIN 0148x, (assembly) stamped AP_9_17_64. No casting # on the cover. Has an NPT plug so it must be and early '65 hybrid. Third pic is off a January '64 4.56 diff that I have with a "303" cover with the fine thread plug (compared to the NPT).

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[Joe L.]

Re: 64 rear diff cover

Here's what I believe is the original rear cover off my '65 VIN 0148x, (assembly) stamped AP_9_17_65. No casting # on the cover. Has an NPT plug so it must be and early '65 hybrid.

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Wayne------


Are you sure that plug is NPT thread? From what I can see of it, it looks more like machine thread to me.

[Wayne M.]

Re: 64 rear diff cover

Are you sure that plug is NPT thread? From what I can see of it, it looks more like machine thread to me.

Joe --- Did you have a chance to check the 3rd pic that I added in an edit ? Shows a mid-'64 cover with fine thread hole and plug (at the top), with the NPT plug from my late '65 "375" cover below it.

[Gary R.]

Re: 64 rear diff cover

Wayne

Wasn't there a washer with the 63-64 machine plugs.

[Joe L.]

Re: 64 rear diff cover

Joe --- Did you have a chance to check the 3rd pic that I added in an edit ? Shows a mid-'64 cover with fine thread hole and plug (at the top), with the NPT plug from my late '65 "375" cover below it.

Wayne------


Yes, I see it now; you must have added it after I posted. However, the very first picture you posted of the 3830303 cover looks to me like it has a machine thread plug, not an NPT. If so, I don't understand how it would be a hybrid.

[Timothy B.]

Re: 64 rear diff cover

Wayne

Wasn't there a washer with the 63-64 machine plugs.

Hi Gary,

There has to be a sealing washer, on mine I had to buy a repro washer that in no way seals. If you have seen the correct washer in your comings and goings post it's size and material so I know what the original looks like.