FA Code on rear housing

[Jason Upshaw]

Hi everyone,

I changed the rear gear in my Father-in-laws '64 365 hp this weekend to a 3.55 unit for better interstate drivability. The housing that was in the car has a code of FA 7 15 66 . Am I correct in thinking that this is a 3.70:1 posi unit for a '66 427? I know that the unit was not correct for the car. Could someone deciper the date codes for me? I lent a friend of mine my "Corvette by the numbers" book so I can't look it up myself. I want the correct information when I put the unit up for sale so no one is misled.

Thanks,
Jason U.
'60 245hp
'71 Conv.

[Jack H.]

Re: FA Code on rear housing

According to Noland Adams, the FA broadcast code used on posi rear end in '66 indicated an L79 (SB) with M21 manual trans power plant configuration.

[John H.]

Re: FA Code on rear housing

Jason -

The Spec Guide shows "FA" as 3.70 Posi for 4-speed 396/427 usage; the stamp on yours indicates it was made on July 15, 1966 (which was two weeks before the end of the '66 model year), so it could have originally been installed in a late '66 or an early '67.

[Wayne M.]

Re: FA Code on rear housing

Jack -- You were reading the ECL (Exception Control Letter) code for option G81 (Positraction Rear Axle), which is, as you say, the code for L79 w/M21, and this would be found on the window sticker, appearing as 02G81FA in the left RPO column. But the factory stamped code on the carrier is, as Mr. Hinckley says, for a 427.

Don't know why GM made the two coding systems so similar, but it leads to confusion 35 years later.

[Jason Upshaw]

Re: FA Code on rear housing

Thanks everyone for the help. The information you have given me confirms what I thought. Thanks again, Jason