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3.70 posi


Jim F. Garrett

Just acquired a red conv. '65. Have considerable amount of
receipts, etc. One of these shows a "remove/replace the
3.70 rear end". I'm new to this but from a cursory look at some
of the literature, it looks as though this ratio was only available
with the close ratio 4 spd (which this car does not have)...
apprec confirmation/clarification re this.
Thanks, Jim

Welcome to the CAC Jim.

I see a code AO 3.70 positraction listed for 4 speed (327). This would appear to be any 4 speed 327. I also see a code AS 3.70 standard rear, not posi, listed for a close ratio 4 speed (327) only. I'll bet this is really rare. Then a FA 3.70 posi for big blocks.

I never noticed that before but clear back to '59 they list a 3.70 non posi for a close ratio or performance application only.

My conclusion is that a 3.70 posi was available with any 4 speed (327) and a 3.70 non-posi was only available with the close ratio 4 speed. The only other non posi was a 3.36. Of course that doesn't mean it could not have been rebuilt and the posi unit removed or that a 3.70 ring and pinion was substituted for a different gear. Is there a code tag on one of the cover bolts? Is it a posi? Code tags are thrown away often by rebuilders.

Let us know what you find.
Hi, Jim - welcome aboard (I just signed in the other day myself)!

In '65, the only 327 engine you could get a 3.70 with was the L-79 (327/350), with the close-ratio 4-speed. The base (250hp) and L-75 (300hp) 4-speeds were all wide-ratio, and were available only with 3.08 and 3.36 axles. The L-79 350hp only came with the close-ratio 4-speed, with the 3.70 as standard, and 3.55 and 4.11 were optional (3.55 and 3.70 were available open or Posi, 4.11 was Posi only).

A dealer could request an override to the approved combinations, but it would have to be approved by the Zone Office.

Of course, lots of things can happen to our Corvettes over 36 years of owners - trying to run those things down is half the fun!

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