1969 three digit axle codes

[Edward B.]

I don't know if the 5th edition is different, but the 4th edition TIM&JG states that starting AFTER October, 1969, the rear axle was stamped with the 1970 model year 3 digit code. My car was assembled on October 21st, 1969 and the axle assembly date is October 6th, 1969 and it has the 3 digit code (CAT). Am I missing something or should the TIM&JG state starting IN October, 1969...?

Thanks
Ed

[Edward J.]

Re: 1969 three digit axle codes

Ed those dates line up

[Edward B.]

Re: 1969 three digit axle codes

So exactly WHEN did they start using the 1970 model year three digit codes? Apparently, if my dates line up, then the TIM&JG is incorrect. (At least the 4th edition. I don't have the 5th, so I can't compare.)

Ed

[Mike E.]

Re: 1969 three digit axle codes

Any TIM&JG can only reflect two things. 1) GM documentation, and 2) observations gleaned from original cars.
At some point in the past, contributors to the JG observed that late 69’s had the three digit code. The earliest known to those who contributed to the 4th edition of the manual was obviously in November. Your car would obviously indicate differently.
However, did the three-digit stamping begin on the same day with all late 69 diffs, or with certain gear ratios, followed later (in November?) with other gear ratios as they were needed?
Over the years, in my contributing to at least 8 JG’s (and chairing two of them) I cannot begin to tell you how many times I have heard “well, MY car has...........”, and many of those observations were helpful. Others were by self-serving owners who had installed an incorrect part on their car and were trying to get it legitimized by the manual.
Producing an accurate manual is difficult and thankless. Look at it as a textbook. Those change as they reflect further gained knowledge and understanding. E.g. The earth is flat.
AND, case in point, the 5th edition wording says “Those 1969 cars produced after September 1969 have 1970 differential codes.”

[Edward B.]

Re: 1969 three digit axle codes

Mike, I wasn't trying to belittle the authors of the TIM&JG. Quite the contrary, it's a TOUGH AND THANKLESS job as you stated, and I reference it CONSTANTLY!!! I was just curious as to why my car has the 3 digit code when it (according to the 4th edition TIM&JG) shouldn't.

So it looks like I'll need to spring for the 5th edition.

And because no one says it much... THANK YOU!

Ed

[Larry E.]

Re: 1969 three digit axle codes

Mike, I wasn't trying to belittle the authors of the TIM&JG. Quite the contrary, it's a TOUGH AND THANKLESS job as you stated, and I reference it CONSTANTLY!!! I was just curious as to why my car has the 3 digit code when it (according to the 4th edition TIM&JG) shouldn't.

So it looks like I'll need to spring for the 5th edition.

And because no one says it much... THANK YOU!

Ed

Ed>What gear ratio do you have? FWIW>I have seen some older axle's that have 2 digit codes but have Julian Dates with them instead
of the normal M/D/Y. Most of the ones in question are
the rarer ones like the 4:56 ratio. Not sure if this is correct or not. Larry

[Edward B.]

Re: 1969 three digit axle codes

Larry, the stamp is really light, but it's "2 CAT 10 6 69 W". That decodes as the 2nd shift, 3.08 Posi Heavy Duty, October 6th, 1969, Warren, MI.

Ed

[Terry M.]

Re: 1969 three digit axle codes

Mike, I wasn't trying to belittle the authors of the TIM&JG. Quite the contrary, it's a TOUGH AND THANKLESS job as you stated, and I reference it CONSTANTLY!!! I was just curious as to why my car has the 3 digit code when it (according to the 4th edition TIM&JG) shouldn't.

So it looks like I'll need to spring for the 5th edition.

And because no one says it much... THANK YOU!

Ed

Ed
Another point with respect to collecting data. Differential codes are one of the most difficult to accumulate. We have less adta on those than most any other aspect of Corvettes just because of the difficulty of getting to them as the car sits on the ground. As a result we are less able to judge this feature.

Also one should take any of the change dates shown in the TIM&JG with a grain of salt for the reasons above and those Mike puts forward. As I said in another thread over the weekend: Changes in the JM take place through enough communication with the appropriate JM Coordinator and/or the appropriate National Team Leader, but patience is required due to the normal time between manual revisions running into years.

Thanks to you for helping us make the manual more relivant.

[Terry M.]

Re: 1969 three digit axle codes

Any TIM&JG can only reflect two things. 1) GM documentation, and 2) observations gleaned from original cars.
At some point in the past, contributors to the JG observed that late 69’s had the three digit code. The earliest known to those who contributed to the 4th edition of the manual was obviously in November. Your car would obviously indicate differently.
However, did the three-digit stamping begin on the same day with all late 69 diffs, or with certain gear ratios, followed later (in November?) with other gear ratios as they were needed?
Over the years, in my contributing to at least 8 JG’s (and chairing two of them) I cannot begin to tell you how many times I have heard “well, MY car has...........”, and many of those observations were helpful. Others were by self-serving owners who had installed an incorrect part on their car and were trying to get it legitimized by the manual.
Producing an accurate manual is difficult and thankless. Look at it as a textbook. Those change as they reflect further gained knowledge and understanding. E.g. The earth is flat.
AND, case in point, the 5th edition wording says “Those 1969 cars produced after September 1969 have 1970 differential codes.”

Mike
I admire your diplomacy. You haven't lost your professional touch yet. Congratulations.

[Gary B.]

Re: 1969 three digit axle codes

Post a good picture if you can. It may end up in the 6th Edition some day....

Gary Bosselman

[Edward B.]

Re: 1969 three digit axle codes

Another point with respect to collecting data. Differential codes are one of the most difficult to accumulate. We have less adta on those than most any other aspect of Corvettes just because of the difficulty of getting to them as the car sits on the ground. As a result we are less able to judge this feature.

That's the same issue we have at the Camaro Research Group Terry! As a matter of fact, we're currently having a discussion on late 1969 Camaro axles being "peened" to remove the "C" before the suffix code. Which is why I posted the Corvette information from my car. As far as I can tell, none of the late 1969 codes were "peened" like the ones on the late 69 Camaro. And even those seem to be hit or miss!!

Post a good picture if you can. It may end up in the 6th Edition some day....

If you can wait till it gets a little warmer, I'll be happy to send you a picture!!

Ed

[Mark D.]

Re: 1969 three digit axle codes

Ed
If you’re on the CRG as an advisor, you should know better than to ask “exactly” when something changed, as you did above.
Mark

[Edward B.]

Re: 1969 three digit axle codes

Sorry. Won't happen again.

Ed

[Chris H.]

Re: 1969 three digit axle codes

Here’s my diff stamp from my old ‘70 LS5, build date Jan 9, 1970.