Rear Diff : Any help decoding what I have?
Race Director
Joined: Oct 2000
Posts: 12,687
Likes: 3,139
From: Shamong, NJ
"AY" is a 2.73 rear, "W" is Warren (where it was assembled), 331 is the Julian date is was assembled (the 331st day of the year), "E" is Eaton, the maker of the Posi unit and "2" is the plant shift it was assembled. I believe "AY" was only used in 75.
"AW" is a 3.08 rear, assembled at Warren on the 55th day (055) of the year using an Eaton Posi on the second shift. "AW" was the code for 3.08's in 71, 73, 74, & 75.
"AW" is a 3.08 rear, assembled at Warren on the 55th day (055) of the year using an Eaton Posi on the second shift. "AW" was the code for 3.08's in 71, 73, 74, & 75.
Thread Starter
Team Owner
Joined: Feb 1999
Posts: 34,455
Likes: 665
From: Republic of Texas
Thread Starter
Team Owner
Joined: Feb 1999
Posts: 34,455
Likes: 665
From: Republic of Texas
Now the dilemma... the 2.73 rear is current installed in my '68 which now has a mildly modded LS2 and 6 speed manual (double OD). I assume over the years the original '68 diff blew ( my father owned a restoration business/speed shop) and installed another diff he had laying around. I didn't feel any lack of gearing with the torque of the Big Block I had installed. In the current set up at 70mph I'm turning 1350rpms, but I can hear the radio and hold a conversation with the passenger.
I don't race it, but also know how much fun the 3.73s were in my other car. HmmmBeing that none of gears the sets outside of Tom's is American made anymore, would I be better off trying to find another diff with the original gear ratios that I want or have it rebuilt with new (likely foreign) gears?
Last edited by Corey_68; Apr 29, 2024 at 05:16 PM.
Tech Contributor
Joined: Aug 1999
Posts: 15,188
Likes: 4,010
From: Connecticut, USA
Rather than relying on housing stamping, especially on a used diff, open it up and confirm what you have.
There are no new usa made gear sets left. The last company - US Gear- closed 3-4 years ago. They made the gears for Toms as well as selling direct. All the new gears sold today are imported. I still have stock of NOS US Gear but won't sell them and if I do they would be $650 easy. You have Yukon, Motive, Richmond and reboxed gear sets sold today- all imported.
There are no new usa made gear sets left. The last company - US Gear- closed 3-4 years ago. They made the gears for Toms as well as selling direct. All the new gears sold today are imported. I still have stock of NOS US Gear but won't sell them and if I do they would be $650 easy. You have Yukon, Motive, Richmond and reboxed gear sets sold today- all imported.
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Thread Starter
Team Owner
Joined: Feb 1999
Posts: 34,455
Likes: 665
From: Republic of Texas
Rather than relying on housing stamping, especially on a used diff, open it up and confirm what you have.
There are no new usa made gear sets left. The last company - US Gear- closed 3-4 years ago. They made the gears for Toms as well as selling direct. All the new gears sold today are imported. I still have stock of NOS US Gear but won't sell them and if I do they would be $650 easy. You have Yukon, Motive, Richmond and reboxed gear sets sold today- all imported.
There are no new usa made gear sets left. The last company - US Gear- closed 3-4 years ago. They made the gears for Toms as well as selling direct. All the new gears sold today are imported. I still have stock of NOS US Gear but won't sell them and if I do they would be $650 easy. You have Yukon, Motive, Richmond and reboxed gear sets sold today- all imported.
Yep that is my plan.... appreciate the information.
Last edited by Corey_68; Apr 30, 2024 at 12:35 PM.