On my 71, I finally determined the differential gears to be 3.36 by cross-referencing the first 2 letters on the axle which are LR.

Easy enough.

However, when reviewing the cross-reference page I noticed there is another 3.36 but the letters are AX. No other gear ratio has 2 codes.

As far as I know both are posi-traction. But why the different codes. I know this was also done in other years. An inquiring mind wants to know.

Thanks


[Modified by 1971Ultra, 8:27 PM 12/29/2003]

 

I'll bump it to the top for ya!

Larry

 

The "AX" broadcast code rear axle (also "CAX" used in late 1969 and 1970) was a heavy duty 3.36 differential assembly originally intended for use with Corvettes equipped with a solid lifter big block engine and automatic transmission. These differentials definitely had the cap/bolt style halfshaft yokes, but I'm not certain if they also had special gears as well (as was the case in the COPO 9560 and 9561 Camaro "BE" axle)... I've never seen the bill of materials for an "AX" differential so I just don't know. Regardless, I doubt that any heavy duty parts for this differential (with the exception of the side yokes) would have extended beyond the 1969 model year.

The cap/bolt side yokes were originally used only behind big block engines, but they were gradually phased into other production applications as well... LT-1s, for example, received these "heavy duty" differentials when that engine was introduced in 1970... Some small block/M-40 cars (when equipped with specific options) used them as well. There were, however, some Corvette differentials that still used a u-bolt to retain the halfshaft universal joint.

The "base" Corvette beginning with 1970 was equipped with the base 350 engine, a four speed manual transmission, and a positraction rear axle with a 3.36 to 1 ratio. My guess is that this standard 3.36 rear axle was the "CLR" code ("LR" code in the case of later years) the one used in this standard duty application and I'm willing to bet it used the u-bolt style side yokes.

So the big question... What was originally installed in your 1971 Corvette? If I had to bet, I'd guess that it is a base engine (ZQ3) backed by an M-20 transmission.

Regards,

 

Yes - drivetrainwise this car was originally a base model with the 350/270hp, M20 4-speed.

Based on your insight, it would make sense that this car was equipped with the standard differential instead of what may be the much more desired HD differential.

It is odd, that in the 4 or 5 books I have reviewed, none of them described the difference between the LR and AX code.

Thanks