Correct Rear-end for 1970 LS-5?

[Tony H.]

I own a 1970 LS-5 with M-21, PS, alarm, AM/FM radio, black leather interior, Laguna Gray, and rwl Goodyear Speedways. According to the tank sticker, there is no optional rear-end ratio listed so I believe that this car would have been equiped with 3.36:1 ratio with positraction. The car is late 1970 production, VIN S415900+ with a build date of July 20, 1970. What are the correct date range and call letters for this particular rear-end? The 1970-72 NCRS Judging Manual, 2nd Ed, seems to indicate that more than one set of letters would fit this car. The letters that seem to match are: CAU and CAX (and perhaps others). Has this section of the manual been revised since this Spring 1993 printing?

[Joe L.]

Re: Correct Rear-end for 1970 LS-5?

Tony----

You are correct; 3.36:1 rear axle was the standard axle for 1970 LS-5 with M-21 4-speed. If no other optional ratio is shown on the tank sticker, the 3.36 is what your car should have.

As far as rear axle codes go, your car should have a "CAX" or "CAU"; either code was apparently used. As far as date is concerned, in my opinion the build date of the axle should precede the car's assembly by 2-8 weeks. But that's just an estimate; don't throw away your "pumpkin" if it falls outside of that range. Chances are, if it shows either of the above 2 codes, it's original.