69427

Quite a while back when I had the rear end out I misplaced the two bolts that fasten the pinion bracket to the bottom of the housing. I managed to find two mismatched factory looking 7/16" bolts (of some unknown origin) and use them, but over the winter I'd like to look around the shop and find the right bolt(s). Can anyone tell me what the factory bolts look like? One of the bolts I have has an integral washer on the head, while the other has a drilled hole at the end for a castle nut and cotter key. They're both about 5" long.

If someone can tell me which (if either) is the correct bolt, and for extra points, what the other bolt might have been for, I'd greatly appreciate it.

Thanks!

TimAT

I'll be back home Monday- you're welcome to come take a look at mine.

69427

Thanks, Tim. I'm tied up with family crap all next week, but I'm still interested in stopping by to see your car one of these weeks when your travel schedule/home-time permits.

Alan 71

Hi,
Perhaps something like this?
(But without the flat and lock washers.)
Regards,
Alan

jr73

If no one beats me to it Ill go out to my shop and look. My body is off and it will be easy to check.

jr73

that was fast

69427

That's one of them I'm using. (Man, I would have bet the other bolt was the correct one.) Well, now I know what to look for.

Thanks Alan.

Nowhere Man

Alan do you know when St. Louis changed the congratulation of those two bolts? on mid years only one bolt got the cotter key and the bolts were opposite of each other

CanadaGrant

My 69 is the exact same as Alan's and the bolts only go in one way with the head on the driver's side.

Nowhere Man

I am thinking sometime in the C3 era they changed that bracket. So maybe that's when they changed the bolt configuration

croaker

Just did this only go in from drivers side on my 75. Also I might add I used the originals not the ones I got in a suspension kit those were a little short. Not as meaty either.

loup68

Original 68 one's did not have that extra reinforcement plate welded where the bolts go on each side. I do not know if late 68's had the heavier duty one. Lou.

69427

Ya got me curious. I dug through some boxes for my lost bracket bolt, and actually found two, but one is about 3/16-1/4" shorter than the other two I have. Got me wondering if any chance the '68 bolts are shorter due to the lack of the reinforcement plates on the bracket.

Alan 71

Hi 69,
I'd think so, but if someone could post the part # for the bolts in both the 68 and 69 AIM, that would verify if they're the same or different.
?
Regards,
Alan

CanadaGrant

69 bolt part number is 3921658. Both the same.

Alan 71

Hi CG,
That's the number in the 71 AIM too.
Regards,
Alan

Lou should likely be able to help with the 68 number.

loup68

I have two 68 AIM's. The newer version very clearly shows the differential bracket without the reinforcement, on the sides. The 68 bracket number is 3868799. There are two different bolt numbers! The forward bolt is number 3846867. It gets a castle nut and a cotter pin. The diagram shows that a flat washer was welded around the outside hole, I think that I remember that feature. The bolt closer to the body of the differential, in other words the rear most bolt is number 193490 and it gets a nut and a lock washer.
The 68 automatic section does show the bracket with the reinforcement. It is number 3921657 and they only show one bolt, but you obviously need two. They are number 3921658, and they get a castle nut and cotter pin. So automatic 68's got the reinforced bracket. Lou.

loup68

I Just checked my older, ORIGINAL AIM copy, and the part numbers are the same. For you newer Corvette owners, if it wasn't for Mid America Enterprises to have the foresight to salvage these assembly plant manuals, we would all be clueless now! Mid America Enterprises was the first Corvette parts company, that I remember. They are now called Mid America Motorworks.
My two AIMS, a 68 and a 69 all have " Chevrolet drafting graphic " at the top left and then assembly instructions at the top right of the pages. Everyone complains that there is no index for the AIMS. These AIMS have an index in the front and use the H number at the top of the pages, or sometimes it is at the bottom.
Why all of the newer AIM copies do not have the front index and the H numbers is a mystery to me. Lou.

Alan 71

Hi Lou,
I agree that the AIM is the most important and useful source of information we have.
It's invaluable to someone taking a car apart and putting it back together.
Here's some information about the AIMs written as only the restorer's friend John Hinkley can!
What a treasure he is!
Regards,
Alan

He wrote it for the Camaro group but applies to what we use too.

http://www.camaros.org/AIM.shtml

loup68

Thank you for posting that link, Alan. I was surprised to find out that only one or two complete AIM copies were in the whole assembly plant, making a complete one really rare! Lou.