1963 Rear End Ratio Question

[Gerald C.]

My 300 hp 4 speed car's rear differential reads "CA" plus the date. If I'm not mistaken, the CA is a 3:36 Non-Positraction. Yet when I look up the specifications on how many 63's were made with this non-posi designation, all I find are the stats on the G81 Positraction and they made 6,855 of these 3:36's. I looked in Noland Adams book and there is nothing mentioned there that I could find.

Is there anywhere I could look to find that production number of 3:36 non-posi for 1963 with the L75 motor?

Thanks

[Jim L.]

Re: 1963 Rear End Ratio Question

Is there anywhere I could look to find that production number of 3:36 non-posi for 1963 with the L75 motor?

Thanks

The best you'll be able to do is a statistical approximation. First determine how many non-Posi 3.36 diffs were made and how many L75 engines were made. You could then figure the fraction of each vis a vis total production. Then multiply those two fractions together and you'll have a 0th order approximation of how many L75s came with non-Posi 3.36 diffs.

[Gerald C.]

Re: 1963 Rear End Ratio Question

Jim,

Thanks for your response. My question is where do I find the number of 3:36 non-Posi's that were made? I can't find that total number. I'll then calculate to as close as I can.

Jerry

[Jim L.]

Re: 1963 Rear End Ratio Question

Good question. I don't know the answer, though.

[Gerald C.]

Re: 1963 Rear End Ratio Question

Thanks! I'm sure the 63 gurus out there will have the answer!

[Gerald C.]

Re: 1963 Rear End Ratio Question

Does anyone know how many CX 3:70 non-posi's are out there? Just trying a different approach.

[Duke W.]

Re: 1963 Rear End Ratio Question

According to the NCRS Spec Guide total '63 G-81 production was 17554 plus 211 G-91 (3.08 open diff) options out of total production of 21513, so the total of open 3.36 and 3.70 open diff. axles is 3748.

The 3.70 open diff. axle was ONLY paired with the 340/360 HP engines with the optional four-speed and NO Positraction option. It's hard to imagine anyone would order those SHP/FI engine with the optional four-speed and opt NOT to spend $43.05 for G-81. My guess is that the vast majority or open diff. 3.36 axles were installed on 250/300 HP engines, which was the standard axle on these engines for ALL transmissions.

A 3.36 open diff. axle was also standard (with no optional ratios, either open diff. or Positraction) on SHP/FI engines with the standard three-speed transmission and their might have been a few of those.

There's no way to get the actual exact number you are looking for.

Duke

[Gerald C.]

Re: 1963 Rear End Ratio Question

Thanks to a few members feedback, I came up with this spreadsheet for rear differential allocations to the various rear end ratios. It is as accurate as I can go based on the feedback and lack of real specific information on the non-posi differentials. If anyone sees any glaring errors, let me know and I'll fix the spreadsheet. But based on the information I've discovered and received, this should be pretty close.
ThanksRear End Calculations.jpg