Where's the rear axle code stamped on a '59?

[Norris W.]

I remember finding it somewhere on my '62, but no luck so far on this one. I can't seem to find one of my straight axle judging manuals either.

[Joe L.]

Re: Where's the rear axle code stamped on a '59?

I remember finding it somewhere on my '62, but no luck so far on this one. I can't seem to find one of my straight axle judging manuals either.

Norris------


C1 rear axle codes were on a metal tag attached to one of the differential studs. If someone has previously removed it, you're out of luck. Reproductions are available, though.

[Stephen R.]

Re: Where's the rear axle code stamped on a '59?

I believe that it's stamped on the forward, passenger side, front facing of the case.

[Norris W.]

Re: Where's the rear axle code stamped on a '59?

Thanks guys. I thought I found it on my '62 when I was verifying the 4.56's the sticker shows, but maybe I counted the ring & pinion since the chunk is out of the car. I spent time yesterday with a rag & wire toothbrush and couldn't get anywhere with the 59 although everything under there is nasty enough to have never been removed. It's up on a lift so I can see it well and didn't notice a tag under any of the bolts.

[Gary C.]

Re: Where's the rear axle code stamped on a '59?

Norris, stamped code on Drivers side & sometimes faint. No code could be OTC service replacement? What's the cast date? Gary....

[Norris W.]

Re: Where's the rear axle code stamped on a '59?

Don't know Gary. I'll take a look Monday. It's so nasty that it takes a good bit of rubbin' and scrapin' to see anything. I'd be surprised if it's ever been out, but a lotta' stuff happens in 45 yrs.

[Ian G.]

Re: Where's the rear axle code stamped on a '59?

Hey Joe, I think the tags are blank. Just different shapes based on the ratio...

[Chuck G.]

Re: Where's the rear axle code stamped on a '59?

Hey Joe, I think the tags are blank. Just different shapes based on the ratio...

Like these.

[Tom P.]

Re: Where's the rear axle code stamped on a '59?

Like these.

Those are incorrect (specifically, the 3.36-3.55). I have preached this for years-----------------------FINALLY, NCRS has made the change.
This is the correct version. The disc is attached at the 2 o:clock position stud for the center case.
BUT THE AFTERMARKET VENDORS WHO SELL THESE REPO TAGS STILL REFUSE TO MAKE THE CHANGE!!!!!!!!


ALLLLLLLL 56-62 rears have a CAST date code next to the casting number on the DRIVER side of the case. The CASTING date includes month(A-L), day, year, similar to below.




IF THE REAR IS A FACTORY POSITRACTION, then the case will also have a big P cast on it, as below. Posi was NOT available until the end of Dec 56. The first (57) posi cases had nothing indicating posi (except for the 3743833 casting number). About Feb 57, the case had an X (next to casting number) for posi. Then about late Mar or Apr, all posi cases got the big P thereafter.


BUT BEWARE, there were TWO distinctly different P configurations------------a thin P and a thick P.
ONLY THE THIN P is correct for a Corvette. The cases with the thin P came from the Detroit Gear and Axle plant and they were used in BOTH Corvettes and pass cars. The cases with the thick P came from the Buffalo (NY) plant and were used ONLY in pass cars.
Here is a thick P posi case.


Also, in the CAST date, the last number(s) is the year. The Detroit cases have ONE number for the year, such as 7 for 1957.
The Buffalo cases have two numbers for the year, such as 57 for 1957. Remember, only Detroit rear end cases went into Vettes, so if the cast date had two numbers for the year, that was ONLY a pass car rear.


BOTH the gear ratio (posi and/or NON-posi) AND the assembly date (mo-day only, the year was included in the casting date) were STAMPED on the PASSENGER side of the case, as seen below. The codes include two letters and 2-4 numbers.
Depending on the individual worker who was doing the stamping, some codes were VERY faintly stamped (nearly impossible to see) and some workers used a sledge hammer to stamp in the code. The codes are stamped in the same maner and location for both pass car and Vette rears, but the two letters are different for Vettes and pass cars.

[Norris W.]

Re: Where's the rear axle code stamped on a '59?

Thanks guys. Found the casting date E ? 9, the thin P just like in the picture, the stamped code in the pass side, also just like in the picture AP (4:11) and believe it's original to the car. From the quarter inch of crap I had to remove it looks like it may've been right there forever, but there's no tag under any of the nuts.

[Gary C.]

Re: Where's the rear axle code stamped on a '59?

Norris,

Tag would've been under the 2 o'clock nut.

Do the nuts have copper washers under them? If not, then IMHO the pumpkin's might have been removed at some time.

Gary
....

[Norris W.]

Re: Where's the rear axle code stamped on a '59?

Gary, I knew about the copper washers, but didn't think to look for them. The rear is VERY dirty. I've had this car for over 10 years, maybe 15 even, but have never seen it on a lift until last week. I'll look for the washers tomorrow. There's no sign that there was a tag on the stud at 2 oclock, but a lot of things change in 45 years. All of the original drivetrain components seem to be intact and the chunk date is in keeping with the rest of the casting dates, but I guess it could've been out for a change to a higher ratio and then changed back, or just for service. I haven't counted it to see if it's still 4:11, but I guess somebody could have had it out to change the ring & pinion also. The rear wheels rotate easily in opposite directions, indicating to trace of a posi, so either it's completely worn out or something's missing. At this point all we know is it's likely to have the original housing.

[Mike E.]

Re: Where's the rear axle code stamped on a '59?

Did all 59's have copper washers? A later 59 I helped with had original rear with original tag , and no washers. 61-62's definitely did not have them.

[Tom P.]

Re: Where's the rear axle code stamped on a '59?

Mike,
I'm so glad that you asked that. I didn't even think about that when it was asked earlier.
I cannot positively say for Corvettes, but for 55-57 pass cars, AS FAR AS I KNOW, 55-57 used nuts with seperate copper washers. Then in 58 (and I would guess it was the same for Vettes), the nuts had integral (steel) washers. But on all my rear installations, I use regular nuts and copper washers. I'm of the opinion, that as the copper washer crushes, it makes a better seal against oil weepage from around the stud threads.

[Bill M.]

Re: Where's the rear axle code stamped on a '59?

The rear wheels rotate easily in opposite directions, indicating to trace of a posi, so either it's completely worn out or something's missing. At this point all we know is it's likely to have the original housing.

The early posi units did not have a pre-load on the clutch pack. The free-hanging wheels would rotate in opposite directions when brand new. There is a ramp designed into the posi case that locked up the clutch pack as torque was applied. That changed in 1960 when Belleville washers were included in the clutch pack to provide a pre-load.