1975 Corvette Differential Code AOW 111 E1

[Timothy B.]

I am working on a very original low mile (27,000) 1975 corvette convertible that has a rear housing with a stamped code of AOW 111 E1.

This rear is a 3.70 ratio (I have checked) and looks to me like it's never been out of the car. I can find no information about a AO stamping for 1975 and I wanted to see if anyone has any information or has ever seen this code on a 75. The car was built June 30, 1975 so if the 111 is a julian date that would jive with the car dates.

This car has an all original low hp 350 with a super T-10 wide box and 370 axle. It's been in storage since 1978 and must have been stored in a garage where there was very low humidity because there is hardly any surface rust on the frame, the car looks like it was parked last week. This car still had the original Firestone 500's mounted.

The paperwork (service invoices etc.) since new makes no indication about a rear axle change except a leak at the rear. Looking at the pumpkin there looks to be silicone pushed out around the cover but I don't know if the sealer was used in place of a cover gasket in 1975.

Any comments on this rear are appreciated, I will try to post a picture showing the code. The area of the pumpkin that shows the casting date looks like it's cast O N 1, I have no idea what this could mean.

Thanks, Tim

[Edward B.]

Re: 1975 Corvette Differential Code AOW 111 E1

Tim, I've run into that format twice before.

Where the format SHOULD be Ratio/Julian Date/Posi/Shift/Factory (i.e. AO 111 E1 W), I've noted in those two instances the format was wrong. It was Ratio/FACTORY/Julian date/Posi/Shift (i.e. AOW 111 E1).

As a matter of fact, a quick Google search found ANOTHER AOW code axle like yours.

Not sure why but I CAN tell you the axle probably isn't original to the car unless it's some kind of factory replacement? The AO code wasn't used in 1975.

Ed

[Gary R.]

Re: 1975 Corvette Differential Code AOW 111 E1

Tim
Regardless of the stampings I would highly recommend you pull the cover if it's out of the car. If original the axle faces will be soft and you want to address this before there are other issues. Typically I have found this year range to have good posi cases, but have the soft axles and snow flake clutches in them.

There would have been a gasket there so sounds like someone was in there before, another reason to inspect it. Could just have been a pinion seal leak but the cover would not have to be pulled for that. Look at the posi case webbing for impact marks, backed out RG bolts are not uncommon with these diff's.

[Timothy B.]

Re: 1975 Corvette Differential Code AOW 111 E1

Thanks Ed and Gary for the information, that article from your link Ed is very interesting. What I am confused about is this AO stamping which indicates a 3.7 axle (which it is) but this code was never used with a Julian date like in the seventies.

The housing on this rear looks like it only has surface rust, I will scrutinize the service records again and post some pictures.