G91 Special Highway Axle

[Paul K.]

I am restoring a 65 coupe 327/300 4 speed, with G91 , can someone tell me what is special about this option G91 Special Highway Axle 3.08:1, available for 63,64,and 65

Paul Klemetson

[Duke W.]

Re: G91 Special Highway Axle

G-91 was a 3.08:1 open differential axle available only with the 250/300 HP engines and M-20 four-speed. The base axle for these two engines with any transmission was also open differential type with a 3.36:1 ratio. Positraction (G-81, $42-43) was available with the base ratio, or 3.08 if M-20 was ordered. Three speed and Powerglide got 3.36 open diff axles as base equipment. G-81 was optional, but only with a 3.36 axle ratio. Three-speed and Powerglide had no optional ratios.

G-91 was a whopping two dollar option.

Base axles for SHP/FI engines were also open diff, 3.36 with the base three-speed manual trans and 3.70 with M-20. Depending on the year and specific engine up to five optional ratios were available from 3.08 to 4.56, and all REQUIRED G-81.

All the above can be discerned from the power train charts in the various Corvette "vehicle information packages" that are a free download from www.gmheritage.com They're also included in the NCRS Specification Guides along with MSRP and production quantities.

I assume you have the 1965 Corvette Shop Manual, 1965 Supplement, and 1965 AIM.

Duike

[Paul K.]

Re: G91 Special Highway Axle

Thanks for the great explanation, I always learn a lot from you and this forum

Paul Klemetson